diff --git a/marked/T/T-REC-T.1-198811-I_PDF-E/raw.md b/marked/T/T-REC-T.1-198811-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..2654794da834e5460d6b4631339e6700fc33d8bd --- /dev/null +++ b/marked/T/T-REC-T.1-198811-I_PDF-E/raw.md @@ -0,0 +1,221 @@ + + +![ITU logo: a globe with the letters ITU and a lightning bolt symbol.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: a globe with the letters ITU and a lightning bolt symbol. + +INTERNATIONAL TELECOMMUNICATION UNION + +# ITU-T + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +## T.1 + +**TERMINAL EQUIPMENT AND PROTOCOLS FOR +TELEMATIC SERVICES** + +--- + +**STANDARDIZATION OF PHOTOTELEGRAPH +APPARATUS** + +**ITU-T Recommendation T.1** + +(Extract from the *Blue Book*) + +--- + +# NOTES + +1 ITU-T Recommendation T.1 was published in Fascicle VII.3 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below). + +2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## Recommendation T.1 + +## STANDARDIZATION OF PHOTOTELEGRAPH APPARATUS + +*(former CCIT Recommendation D.1; amended at +New Delhi, 1960; Geneva, 1964; Mar del Plata, 1968; +Malaga-Torremolinos, 1984 and Melbourne, 1988)* + +The CCITT, + +*considering* + +that the transmission of pictures is possible only if certain characteristics of the transmitting and receiving equipments are identical, + +*unanimously declares the view* + +that phototelegraph apparatus and the associated modulating and demodulating equipment should be constructed and employed according to the following standards: + +### **1 Scanning track** + +At the transmitting apparatus the message area should be scanned in a “negative” direction. The orientation of the document in relation to the scanning plane will depend upon its dimensions and is of no consequence. + +At the receiving apparatus scanning takes place in a “negative” direction for “positive” reception and in a “positive” direction for “negative” reception. + +### **2 Index of cooperation** + +The normal index is 352 (corresponds to a factor of cooperation of 1105). + +The preferred alternative index, for use when less dense scanning is required, or when the characteristics of circuits (and particularly combined radio and metallic circuits) so demand, is 264 (a factor of cooperation of 829). + +The admissible tolerances on the above-mentioned values are $\pm 1\%$ . + +### **3 Dimensions of apparatus** + +#### *3.1 Apparatus with drum scanning* + +The most currently used drum diameters are 66, 70 and 88 mm. + +The drum factor of the sending apparatus shall not be more than 2.4. + +The drum factor of the receiving apparatus shall not be less than 2.4. + +The width of the picture-retaining device (dead sector) may not exceed 15 mm. An allowance of 3% of the total length of a scanning line is also made for phasing. Thus, since the total circumference of a drum of the diameter of 66 mm is about 207 mm, the usable circumference will be at least 186 mm. + +### 3.2 Apparatus with flat-bed scanning + +The total lengths of the most current scanning lines are 207, 220 and 276 mm of which 15 mm are not used for effective transmission, because of the possibility that the receiving station may use a drum apparatus. + +Before transmitting a picture to a receiving station using a drum apparatus, it is necessary to ensure that the value of ratio: + +$$\frac{\text{length of document to be transmitted}^{1)} }{\text{total length of a scanning line}} \times \pi \text{Error! Bookmark not defined.}$$ + +is less or at most equal to the drum factor of the receiver used. + +3.3 Table 1/T.1 gives corresponding values of index of cooperation $M$ , factor of cooperation $C$ , drum diameter $D$ , total length of scanning line $L$ , scanning pitch $P$ and scanning density $F$ for apparatus in most common use. + +TABLE 1/T.1 + +| $M$ | $C$ | $D$ (mm) | $L$ (mm) | $P$ (mm) | $F$ (lines/mm) | +|-----|------|----------|----------|----------|----------------| +| 264 | 829 | 66 | 207 | 1/4 | 4 | +| 264 | 829 | 70 | 220 | 1/3.77 | 3.77 | +| 264 | 829 | 88 | 276 | 1/3 | 3 | +| 350 | 1099 | 70 | 220 | 1/5 | 5 | +| 352 | 1105 | 66 | 207 | 3/16 | 16/3 | +| 352 | 1105 | 88 | 276 | 1/4 | 4 | + +*Note* – The maximum dimensions of the pictures to be transmitted result from the parameters given in the table. + +### 4 Reproduction ratio + +In the case where apparatus working with different lengths of scanning line (but with the same index of cooperation) are interconnected, there will be a slight change in size and the reproduction will bear the same proportion as the original, the ratio being that of the total lengths of the scanning lines. + +### 5 Drum rotation speed – scanning line frequency + +5.1 Table 2/T.1 gives the normal and approved alternative combinations of drum rotation speeds or of scanning line frequencies and indices of cooperation. + +1) Measured in the direction perpendicular to the scanning line. + +TABLE 2/T.1 + +| | Drum rotation speed
in rpm or scanning
line frequency | Index of cooperation | | +|-------------------------------------------------------------------------------------------------|-------------------------------------------------------------|----------------------|-----------------------------------------| +| | | Metallic
circuits | Combined metallic
and radio circuits | +| Normal conditions | 60 | 352 | 352 | +| | 90 | | 264 | +| Alternatives for use when the
phototelegraph apparatus and metallic
circuits are suitable | 90 | 264 and 352 | | +| | 120 | 264 and 352 | | +| | 150 | 264 | | + +*Note 1* – In the case of transmitters operating on metallic circuits, the index 264 is not intended to be used with an 88-mm drum. In the case of transmitters operating on combined metallic and radio circuits, the index 264 associated with a drum diameter of 88-mm is intended to be used only exceptionally. + +*Note 2* – The provisions given in the table are not intended to require the imposition of such standards on users who use their own equipment for the transmission of pictures over leased circuits. However, the characteristics of the apparatus used should be compatible with the characteristics of the circuits used. + +5.2 The speed of transmitters must be maintained as nearly as possible to the nominal speed and in any case within $\pm 10$ parts in $10^6$ of the nominal speed. The speed of receivers must be adjustable and the range of adjustment should be at least $\pm 30$ parts in $10^6$ from the nominal speed. After regulation, the speeds of the transmitting and receiving sets should not differ by more than 10 parts in $10^6$ . + +### 6 Judder + +The stability of the speed during one rotation should be such that the maximum shift of the drum surface from the average position should not exceed one quarter of the scanning pitch $P$ at normal index 352, which means that the maximum angle of the oscillations should not exceed 0.08 degree measured from the average position. + +### 7 Synchronization + +When phototelegraph stations have available a standard of frequency which is better than $\pm 5$ parts in $10^6$ , verification of the synchronism between the two stations may be dispensed with. In view of the saving of time, this method should be adopted wherever possible. + +To compare the speeds of a transmitter and a receiver, an alternating current whose frequency bears an unvarying relationship to the transmitter speed and has a nominal value of 1020 Hz is used. + +Where there is the possibility that the transmitter and receiver may be connected by a circuit liable to introduce frequency drifts, for example, by a carrier telephone circuit, the use of the simple 1020-Hz synchronizing tone is unsatisfactory. The preferred method of overcoming this difficulty is to transmit the phototelegraph carrier (of about 1900 Hz) modulated by the 1020-Hz synchronizing tone. + +At the receiving end, the 1020-Hz synchronizing frequency is restored by detection and can then be used in the normal manner. + +### 8 Phasing + +Phasing is performed after the speeds of the transmitter and receiver drums have been equalized. + +For phasing purposes, the transmitter sends a series of alternating white and black signals in such a way that the black lasts 95% and the white 5% of the total scanning line period (admissible tolerance: $\pm 0.5\%$ of the total duration of a scanning line). The apparatus must be so adjusted that the pulses corresponding to the signal for white are transmitted: + +- during scanning of the “dead sector”, when drum apparatus is used, +- during “lost time”, when flat-bed apparatus is used, + +and that they are placed at the middle of the dead sector (or of the interval corresponding to the lost time). + +(Tolerance admitted in the position of the "white" pulses: $\Delta_E = \pm 1\%$ of a “total scanning line length”.) + +At the receiving station, phasing signals are used to start the apparatus so that short white pulses occur in the middle of the "lost time" (tolerance admitted: $\Delta_R = \pm 2\%$ of a "total scanning line length"). + +*Note* – These tolerances allow for the fact that the restitution of the original may deviate from its nominal position by 3% of a “total scanning line length”, when the sending and receiving stations are operating with the maximum authorized drift in the same direction. + +### 9 Contrast + +The transmitter must transmit the original document without changing the contrast of the tone scales of the picture to be transmitted. + +### 10 Modulation and demodulation equipment + +#### 10.1 Amplitude modulation + +Phototelegraph equipment shall normally provide for transmission and reception of an amplitude-modulated audio-frequency carrier, which is the normal mode of transmission for international metallic circuits. + +The level of the output signal of the transmitter shall be greatest for white and least for black. It is desirable that the ratio of nominal white signal to nominal black signal should be approximately 30 decibels. + +To simplify multi-destination operation and AM/FM conversion for radio operation it is desirable that the amplitude of the transmitted signal should vary linearly with the photocell voltage and that no corrections for tone scale should be made at the phototelegraph transmitting station. + +For audio-frequency telephone circuits, the frequency of the picture carrier-current is fixed at about 1300 Hz. This frequency gives the least delay distortion on lightly loaded underground cables. + +In the case of carrier telephone circuits providing a transmission band from 300 to 3400 Hz, a carrier-current frequency of about 1900 Hz is recommended. + +### 10.2 Frequency modulation + +Preferably phototelegraph apparatus should also provide for transmission and reception of a frequency-modulated audio-frequency carrier for use when necessary: + +- a) on combined metallic and radio circuits; +- b) on wholly metallic circuits. + +In such a case, the characteristics of the frequency-modulated output should be: + +| | | +|----------------------|---------| +| mean frequency..... | 1900 Hz | +| white frequency..... | 1500 Hz | +| black frequency..... | 2300 Hz | + +The deviation of frequency should vary linearly with photocell voltage or, in the case of conversion from amplitude modulation to frequency modulation, with the amplitude of the amplitude-modulated carrier. + +The stability of the transmission must be such that the frequency corresponding to a given tone does not vary by more than 8 Hz in a period of 1 second and by more than 16 Hz in a period of 15 minutes. + +The receiving apparatus must be capable of operating correctly when the drift of black and white frequencies received does not exceed their nominal value by more than $\pm 32$ Hz. + +*Note* - It is recognized that there are difficulties operating with these frequency limits on the public switched telephone network (PSTN) where certain types of signalling equipment are used. By prior agreement between users on the PSTN, alternative frequencies of 1300 Hz for white and 2100 Hz for black may be used. + +### **11 Positive or negative reception** + +Selection of positive or negative reception should be made by adjustment at the receiver. The adaptation of the transmitted signals to the characteristics of the photographic materials must also be effected at the receiving end according to the type of reproduction, negative or positive. + +### **12 Colour transmission (optional)** + +12.1 Phototelegraphy apparatus constructed in accordance with this Recommendation can be used in colour phototelegraphy by splitting the spectrum of light reflected from the picture elements into three basic colours and transmitting the three resulting signals sequentially. Then each signal can be treated and transmitted as a phototelegraphy signal as specified in this Recommendation above. + +12.2 The splitting of light reflected from picture element into three spectral components should be performed simultaneously. Thus synchro and phase coincidence and electronic colour correction can be achieved. + +12.3 The triad RGB (red, green, blue) shall be used as a basis of main colours. The red colour shall be in range of 575-700 nm, green 485-575 nm, blue 400-485 nm. + +*Note* – For the high quality reproduction of art images by means of graphic facilities, transmission of fourth components (i.e. black overtone) is desirable. + +12.4 The order of signal transmission shall be as follows: red, green, blue. In the case of negative reproduction the order of colour separated signals transmission is reversed. + +12.5 The speeds of the transmitting and receiving sets should not differ by more than 1 part in $10^7$ . \ No newline at end of file diff --git a/marked/T/T-REC-T.10-198811-I_PDF-E/raw.md b/marked/T/T-REC-T.10-198811-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..89b28258a716ff84728f9a877c29d8637aca0a58 --- /dev/null +++ b/marked/T/T-REC-T.10-198811-I_PDF-E/raw.md @@ -0,0 +1,70 @@ + + +![ITU logo: a globe with the letters ITU and a lightning bolt symbol.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: a globe with the letters ITU and a lightning bolt symbol. + +INTERNATIONAL TELECOMMUNICATION UNION + +**ITU-T** + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +**T.10** + +**TERMINAL EQUIPMENT AND PROTOCOLS FOR +TELEMATIC SERVICES** + +--- + +**DOCUMENT FACSIMILE TRANSMISSIONS +ON LEASED TELEPHONE - TYPE CIRCUITS** + +**ITU-T Recommendation T.10** + +(Extract from the *Blue Book*) + +--- + +## NOTES + +1 ITU-T Recommendation T.10 was published in Fascicle VII.3 of the *Blue Book*. This file is an extract from the *Blue Book*. While the presentation and layout of the text might be slightly different from the *Blue Book* version, the contents of the file are identical to the *Blue Book* version and copyright conditions remain unchanged (see below). + +2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +## **Recommendation T.10** + +## **DOCUMENT FACSIMILE TRANSMISSIONS ON LEASED TELEPHONE-TYPE CIRCUITS** + +*(Geneva, 1964; amended at Mar del Plata, 1968; +at Geneva, 1972, 1976 and 1980)* + +## **1 Type of circuits to be used** + +The telephone-type circuits used should have characteristics as recommended in Recommendation H.12. + +*Note* – If the leased circuit is used alternately for telephone conversation and facsimile transmission and if the latter is unidirectional, it is not necessary to provide for disabling echo suppressors located on the long-distance leased circuit. However, when such a circuit is used for the simultaneous operation in both directions appropriate measures should be taken to disable echo suppressors before the actual facsimile transmission takes place. + +## **2 Modulation** + +Equipment conforming to Recommendation T.2 or Recommendation T.3 may be used. In the case of Recommendation T.2 equipment, either amplitude or frequency modulation may be chosen. + +## **3 Power** + +The maximum power output of the transmitting apparatus into the line shall not exceed 1 mW whatever the frequency. + +For frequency-modulation equipment conforming to Recommendation T.2, the level at the transmitter output shall be so adjusted that the level of the facsimile and control signals on the trunk circuit does not exceed –13 dBm0 regardless of the type of operation (duplex or simplex). + +For amplitude-modulation equipment conforming to Recommendation T.2, higher black levels may be used provided the mean power in any hour, in one direction of transmission, does not exceed 32 microwatts (–15 dBm0) at the zero relative level point of the trunk circuit. + +For equipment conforming to Recommendation T.3, higher white levels may be used provided the mean power in any hour, in one direction of transmission, does not exceed 32 microwatts (–15 dBm0) at the zero relative level point of the trunk circuit. + +## **4 Multipoint transmission** + +If facsimile transmissions take place simultaneously from a transmitting station to several receiving stations, arrangements shall be made at the junction points so that, on the circuits following the junction points, the same power levels are maintained as those prescribed for individual transmissions. + +## **5 Phase distortion** + +Equipment conforming to Recommendation T.2 should not require any special treatment. However, equipment conforming to Recommendation T.3 may require phase distortion correction in some cases. \ No newline at end of file diff --git a/marked/T/T-REC-T.102-199303-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/T/T-REC-T.102-199303-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..432769edb4f120076609a832501c9e96f79b786b --- /dev/null +++ b/marked/T/T-REC-T.102-199303-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:0552d540738f8daf8c2ee12001b59e5a0f31ed0f04973743379f5397886ecf57 +size 8347 diff --git a/marked/T/T-REC-T.102-199303-I_PDF-E/a738993919a50143787084ee7ce6e2f2_img.jpg b/marked/T/T-REC-T.102-199303-I_PDF-E/a738993919a50143787084ee7ce6e2f2_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..5a2cca46c0f5c74d105c83fedb8f7ed511748ec0 --- /dev/null +++ b/marked/T/T-REC-T.102-199303-I_PDF-E/a738993919a50143787084ee7ce6e2f2_img.jpg @@ -0,0 +1,3 @@ +version https://git-lfs.github.com/spec/v1 +oid sha256:f7d30b7d7736beba340207d0a2b78c30510cc33d3b7e0689a867f4e0fb9c6e75 +size 36759 diff --git a/marked/T/T-REC-T.102-199303-I_PDF-E/raw.md b/marked/T/T-REC-T.102-199303-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..f155d4dbee6a3805a22f2b601eb0b4ec8a09c716 --- /dev/null +++ b/marked/T/T-REC-T.102-199303-I_PDF-E/raw.md @@ -0,0 +1,351 @@ + + +![ITU logo: a globe with the letters ITU inside, and a lightning bolt symbol below it.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: a globe with the letters ITU inside, and a lightning bolt symbol below it. + +INTERNATIONAL TELECOMMUNICATION UNION + +# ITU-T + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +## T.102 + +(03/93) + +**TELEMATIC SERVICES** + +**TERMINAL EQUIPMENTS AND PROTOCOLS +FOR TELEMATIC SERVICES** + +--- + +**SYNTAX-BASED VIDEOTEX END-TO-END +PROTOCOLS FOR THE CIRCUIT MODE ISDN** + +**ITU-T Recommendation T.102** + +(Previously "CCITT Recommendation") + +--- + +# FOREWORD + +The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecommunication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +ITU-T Recommendation T.102 was prepared by the ITU-T Study Group VIII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). + +# --- NOTES + +1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. + +In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. + +2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +# CONTENTS + +| | | Page | +|----|-------------------------------------------------------------|-------------| +| 1 | Scope ..... | 1 | +| 2 | Normative references ..... | 1 | +| 3 | Definitions and abbreviations ..... | 2 | +| | 3.1 Definitions ..... | 2 | +| | 3.2 Abbreviations ..... | 2 | +| 4 | Overview ..... | 2 | +| 5 | Configurations ..... | 2 | +| 6 | General model ..... | 2 | +| | 6.1 Reference configuration ..... | 3 | +| | 6.2 Protocol pillars ..... | 3 | +| 7 | Service definition ..... | 3 | +| 8 | Protocol ..... | 3 | +| 9 | Coding ..... | 3 | +| 10 | Use of CCITT Recommendation X.3 parameters ..... | 4 | +| 11 | Layer 1 ..... | 4 | +| | 11.1 Basic access ..... | 4 | +| | 11.2 Primary rate access ..... | 4 | +| 12 | Layer 2 protocols ..... | 4 | +| | 12.1 Layer 2 protocol for the D-channel ..... | 4 | +| | 12.2 Layer 2 protocol for the B-channel ..... | 4 | +| 13 | Layer 3 protocols ..... | 5 | +| | 13.1 Layer 3 protocol for the D-channel ..... | 5 | +| | 13.1.1 Terminal selection ..... | 5 | +| | 13.1.2 Compatibility checking ..... | 5 | +| | 13.1.3 Service specific use of supplementary services ..... | 5 | +| | 13.1.4 Call progress signals ..... | 5 | +| | 13.2 Layer 3 protocol for the B-channel ..... | 5 | +| 14 | Use of the Bearer Independent Service (BIS) ..... | 5 | +| | 14.1 Out-band procedure ..... | 5 | +| | 14.1.1 Mapping of the BIS to Recommendation Q.931 ..... | 5 | +| | 14.1.1.1 BIS-N-CONNECT ..... | 5 | +| | 14.1.1.2 BIS-N-DISCONNECT ..... | 5 | +| | 14.2 In-band procedure ..... | 5 | +| 15 | Coordination between D- and B-channel ..... | 6 | + + + +# SYNTAX-BASED VIDEOTEX END-TO-END PROTOCOLS FOR THE CIRCUIT MODE ISDN + +(Helsinki, 1993) + +# 1 Scope + +This Recommendation specifies the usage of all protocols and supplementary services up to and including layer 3 for syntax-based Videotex terminal equipment in the ISDN. The scope of this Recommendation is limited to circuit switched calls using the 64 kbit/s unrestricted digital information bearer capability and the DTE/DTE case of the network layer peer entities in B-channel connection. + +This standard is applicable to terminal equipment supporting the syntax-based Videotex using either basic access or primary rate access to the ISDN. In this context, a terminal equipment is either a Videotex terminal, a Videotex service centre, a Videotex access point or a Videotex host. + +This Recommendation is based on other CCITT Recommendations and International Standards and where necessary, it adds new or other requirements as application rules. + +# 2 Normative references + +This Recommendation incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references subsequent amendments to, or revisions of, any of these publications apply to this Recommendation only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. + +- [0] CCITT Recommendation F.300 (1988), *Videotex Service*. +- [1] CCITT Recommendation I.430 (1988), *Integrated Services Digital Network (ISDN) – Basic user-network interface, Layer 1 specification*. +- [2] CCITT Recommendation I.431 (1988), *Integrated Services Digital Network (ISDN) – Primary rate user-network interface, Layer 1 specification*. +- [3] CCITT Recommendation Q.921 (1990), *Integrated Services Digital Network (ISDN) – User-network interface data-link layer specification*. +- [4] CCITT Recommendation Q.931 (1990), *Integrated Services Digital Network (ISDN) – User-network interface Layer 3, specification for basic call control*. +- [5] CCITT Recommendation Q.932 [1988], *Generic Procedures for the Control of ISDN Supplementary Services*. +- [6] CCITT Recommendation T.90 [1991], *Characteristics and Protocols for Terminals for Telematic Services in ISDN*. +- [7] CCITT Recommendation T.105, *Syntax-based Videotex Application Layer Protocol*. +- [8] CCITT Recommendation X.3, *Packet Assembly/Disassembly Facility (PAD) in a Public Data Network*. +- [9] CCITT Recommendation X.75 (1984), *Packet-Switched Signalling System between Public Networks providing Data Transmission Services*. +- [10] ISO/IEC 8208: 1990, *Information Technology – Data Communications – X.25 Packet Layer Protocol for Data Terminal Equipment*. +- [11] ISO 7498, *Information processing systems – Open Systems Interconnection – Basic Reference Model*. + +# 3 Definitions and abbreviations + +## 3.1 Definitions + +For the purposes of this Recommendation, the following definitions apply: + +**data terminal equipment:** See ISO/IEC 8208 [10]. + +**network connection:** See OSI Reference Model ISO 7498 [11]. + +**network layer:** See OSI Reference Model ISO 7498 [11]. + +**packet layer:** See ISO/IEC 8208 [10]. + +**videotex access point:** See CCITT Recommendation F.300 [0]. + +**videotex host:** This term describes a computer which offers one or more applications and/or facilities. It can be represented through a Videotex Host Computer, an External Videotex Host or a Videotex Service Centre. + +**videotex service centre:** See CCITT Recommendation F.300 [0]. + +NOTE – According to CCITT Recommendation F.300 [0], a Videotex Service Centre provides host and/or access functions, i.e. it may also act as a Videotex Access Point. + +**videotex terminal:** See CCITT Recommendation F.300 [0] + +## 3.2 Abbreviations + +For the purpose of this Recommendation, the following abbreviations apply: + +| | | +|------|-------------------------------------| +| BIS | Bearer Independent Service | +| CD | Call Deflection | +| DTE | Data Terminal Equipment | +| ISDN | Integrated Services Digital Network | +| HLC | High Layer Compatibility | +| NSAP | Network Service Access Point | +| SBV | Syntax-based Videotex | +| SUB | Sub-addressing | +| UUS | User-to-User Signalling | + +# 4 Overview + +Clause 4/T.105 [7] applies. + +The following subclauses specify the additional requirements to those as specified in Recommendation T.105 [7] to provide the Bearer Independent Service for syntax-based Videotex (SBV BIS). + +ISDN end-systems conforming to this Recommendation present protocol stacks at the S-or T-reference point as indicated in 6.2. + +# 5 Configurations + +Various configurations and topologies may be used, examples of which are given in informative Annex A/T.105 [7]. It shall be the responsibility of the Videotex Service providers to opt for the appropriate configuration(s) in the definition of the syntax-based Videotex Service. + +# 6 General model + +Clause 6/T.105 [7] applies with the additions given in 6.1 and 6.2. + +## 6.1 Reference configuration + +Figure 1 below illustrates the reference configuration for the DTE/DTE case of connection. The ISDN provides for an end-to-end circuit switched link between the terminal and the Videotex System. + +![Diagram of the reference configuration for the DTE/DTE case of connection. The diagram shows an ISDN SBVT (Syntax-based Videotex Terminal) connected to an ISDN network. The ISDN network is represented by a dashed circle containing two 'E T' (Exchange termination) blocks connected by a line with a cross in the middle. The ISDN SBVT is connected to the first 'E T' block via an 'S/T' (Coincident S- and T-reference point) interface. The second 'E T' block is connected to a 'Videotex System' via another 'S/T' interface. The reference point T0808480-91/d01 is indicated below the Videotex System.](a738993919a50143787084ee7ce6e2f2_img.jpg) + +S/T      Coincident S- and T-reference point +ET      Exchange termination +SBVT    Syntax-based Videotex Terminal + +T0808480-91/d01 + +Diagram of the reference configuration for the DTE/DTE case of connection. The diagram shows an ISDN SBVT (Syntax-based Videotex Terminal) connected to an ISDN network. The ISDN network is represented by a dashed circle containing two 'E T' (Exchange termination) blocks connected by a line with a cross in the middle. The ISDN SBVT is connected to the first 'E T' block via an 'S/T' (Coincident S- and T-reference point) interface. The second 'E T' block is connected to a 'Videotex System' via another 'S/T' interface. The reference point T0808480-91/d01 is indicated below the Videotex System. + +FIGURE 1/T.102 +Reference configuration + +## 6.2 Protocol pillars + +The protocol pillars are given in Figure 2. + +At layer 1, Recommendation I.430 [1] is used for ISDN basic access and Recommendation I.431 [2] is used for ISDN primary rate access. + +At layer 2, Recommendation Q.921 [3] provides for the LAPD data link procedures on the D-channel and Recommendation X.75 [9] provides for the LAPB data link procedures on the B-channel (additional application rules are given in clause 12). + +At layer 3, CCITT Recommendation Q.931 [4] signalling procedures are used on the D-channel, and ISO/IEC 8208 [10] packet level protocol is used in DTE/DTE operation on the B-channel (additional application rules are given in clause 13). + +The provision of the SBV BIS as defined in clause 11/T.105 [7] apply with regard to the mappings of the BIS primitives and parameters to and from the elements (additional rules are given in clause 14). + +# 7 Service definition + +Clause 7/T.105 [7] applies without any additional rule. + +# 8 Protocol + +Clause 8/T.105 [7] applies without any additional rule. + +# 9 Coding + +Clause 9/T.105 [7] applies without any additional rule. + +| | | | +|---|------------------------|---------------| +| 3 | Coordination (Note 1) | | +| | BIS (Note 2) | | +| | Q.931 [4] | ISO 8208 [10] | +| 2 | Q.921 [3] | X.75 [9] | +| 1 | I.431 [2]
I.430 [1] | | +| | Layer | B-channel | + +# NOTES + +1 The coordination function specifies the relationship between D-channel and B-channel protocol pillars. + +2 The syntax-based Videotex Bearer Independent Service (SBV BIS) is defined in clause 11/T.105 [7]. It also covers some aspects of the out-band signalling procedures. + +FIGURE 2/T.102 + +## Protocol pillars + +# 10 Use of CCITT Recommendation X.3 [8] parameters + +In addition to clause 10/T.105 [7], the “X.3 parameter reference number 11” is defined in this Recommendation and shall take the value 18 (64 kbit/s). + +# 11 Layer 1 + +## 11.1 Basic access + +For terminals using the basic access to an ISDN, Recommendation I.430 [1] is applicable without any additional rule. + +## 11.2 Primary rate access + +For terminals using the primary rate access to an ISDN, Recommendation I.431 [2] is applicable without any additional rule. + +# 12 Layer 2 protocols + +## 12.1 Layer 2 protocol for the D-channel + +Subclause 2.2.2/T.90 [6] shall apply without any additional rule. + +## 12.2 Layer 2 protocol for the B-channel + +Subclause 2.2.3/T.90 [6] shall apply without any additional rule. + +# **13 Layer 3 protocols** + +## **13.1 Layer 3 protocol for the D-channel** + +### **13.1.1 Terminal selection** + +Subclause 2.2.4/T.90 [6] shall apply without any additional rule. + +### **13.1.2 Compatibility checking** + +Compatibility checking as part of the access protocol is specified in Annex B/Q.931 and shall apply without any additional rule. + +### **13.1.3 Service specific use of supplementary services** + +The procedures which are required for the use of supplementary services are specified in Recommendation Q.932 [5] and in I.240-Series and I.250-Series Recommendations. + +The use of supplementary services is optional. + +In order to realize some of the configurations mentioned in Annex A/T.105 [7], the following services may be necessary: + +- Sub-addressing (SUB); +- User-to-User Signalling (UUS) Service 1; +- Call Deflection (CD) in combination with UUS Service 1. + +### **13.1.4 Call progress signals** + +Call progress signals may be handled locally by the terminal. + +## **13.2 Layer 3 protocol for the B-channel** + +Subclause 2.2.5/T.90 [6] shall apply. Clause 4/T.90 [6] is also relevant, including the restrictions for Videotex. The use of NSAP does not apply. + +# **14 Use of the Bearer Independent Service (BIS)** + +## **14.1 Out-band procedure** + +The base Recommendation for the layer 3 protocol of the D-channel is Recommendation Q.931 [4] as already mentioned above. Clause 11/T.105 [7] defines the Bearer Independent Service (BIS) for syntax-based Videotex. + +General information about the out-band procedure of the BIS are described in subclause 11.3.1/T.105 [7] and the specific mapping is given below. + +### **14.1.1 Mapping of the BIS to Recommendation Q.931** + +#### **14.1.1.1 BIS-N-CONNECT** + +The protocol elements providing the BIS-N-CONNECT service are carried by the D-channel messages as defined in Table 1. Also the mapping of the parameters is given in Table 1. + +#### **14.1.1.2 BIS-N-DISCONNECT** + +The protocol elements providing the BIS-N-DISCONNECT service are carried by the D-channel messages as defined in Table 2. Also the mapping of the parameters is given in Table 2. + +## **14.2 In-band procedure** + +The service that the network layer entity provides to the Videotex application with respect to the establishment, release and data transfer of network connections, shall be as described in clause 11/T.105 [7]. + +TABLE 1/T.102 +**BIS-N-CONNECT mapping** + +| BIS | D-channel | Reference
Q.931 | +|------------------------------------------------------------------------------------------------------|-------------------------------------------------------|----------------------------------| +| Service primitives | Messages | | +| BIS-N-CONNECT request
BIS-N-CONNECT indication
BIS-N-CONNECT response
BIS-N-CONNECT confirm | SETUP
SETUP
CONNECT
CONNECT | 3.2.9
3.2.9
3.2.3
3.2.3 | +| Parameters | Information elements | | +| Called Address | Called party number
Called party subaddress (Note) | 4.5.8
4.5.9 | +| Calling Address
Responding Address
BIS-user-data | Not used
Not used
User-user | 4.5.29 | +| NOTE – The use of the subaddress is not mandatory and depends on local operation requirements. | | | + +TABLE 2/T.102 +**BIS-N-DISCONNECT mapping** + +| BIS | D-channel | Reference
Q.931 | +|--------------------------------------------------------------|---------------------------------------------------------------|----------------------------------| +| Service primitives | Messages | | +| BIS-N-DISCONNECT request
BIS-N-DISCONNECT indication | DISCONNECT
DISCONNECT or
RELEASE or
RELEASE COMPLETE | 3.2.5
3.2.5
3.2.7
3.2.8 | +| Parameters | Information elements | | +| Originator and Reason
Responding Address
BIS-user-data | Cause
Not used
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a/marked/T/T-REC-T.103-199303-I_PDF-E/raw.md b/marked/T/T-REC-T.103-199303-I_PDF-E/raw.md new file mode 100644 index 0000000000000000000000000000000000000000..3583e45df10236a2a0eae86db7a751e65b5184ea --- /dev/null +++ b/marked/T/T-REC-T.103-199303-I_PDF-E/raw.md @@ -0,0 +1,2805 @@ + + +![ITU logo: a globe with the letters ITU inside, and a lightning bolt symbol below it.](2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg) + +ITU logo: a globe with the letters ITU inside, and a lightning bolt symbol below it. + +INTERNATIONAL TELECOMMUNICATION UNION + +# ITU-T + +TELECOMMUNICATION +STANDARDIZATION SECTOR +OF ITU + +## T.103 + +(03/93) + +**TELEMATIC SERVICES** + +**TERMINAL EQUIPMENTS AND PROTOCOLS +FOR TELEMATIC SERVICES** + +--- + +**SYNTAX-BASED VIDEOTEX END-TO-END +PROTOCOLS FOR THE PACKET +MODE ISDN** + +**ITU-T Recommendation T.103** + +(Previously "CCITT Recommendation") + +--- + +# FOREWORD + +The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecommunication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +ITU-T Recommendation T.103 was prepared by the ITU-T Study Group VIII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). + +# --- NOTES + +1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. + +In order not to delay publication of this Recommendation, no change has been made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. + +2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +# CONTENTS + +| | Page | +|---------------------------------------------------------------------------------------------------------|-------------| +| 1 Scope ..... | 1 | +| 2 Normative references ..... | 1 | +| 3 Definitions and abbreviations ..... | 2 | +| 3.1 Definitions ..... | 2 | +| 3.2 Abbreviations ..... | 3 | +| 4 Introduction ..... | 3 | +| 4.1 General ..... | 3 | +| 4.1.1 X.31 Case A access ..... | 4 | +| 4.1.2 X.31 Case B, B-channel access ..... | 4 | +| 4.1.3 X.31 Case B, D-channel access ..... | 4 | +| 4.2 Reference Configurations ..... | 4 | +| 4.2.1 Using access to PSPDN services (X.31 Case A) ..... | 4 | +| 4.2.2 Using the ISDN virtual circuit service (X.31 Case B) through the B-channel or the D-channel ..... | 4 | +| 4.3 Protocol Pillars ..... | 4 | +| 4.3.1 Using access to PSPDN services (X.31 Case A) ..... | 4 | +| 4.3.2 Using the ISDN virtual circuit service (X.31 Case B) through the B-channel ..... | 8 | +| 4.3.3 Using the ISDN virtual circuit service (X.31 Case B) through the D-channel ..... | 9 | +| 5 Layer 1 ..... | 9 | +| 5.1 Basic access ..... | 9 | +| 5.2 Primary rate access ..... | 10 | +| 6 Access to PSPDN services (X.31 Case A) ..... | 10 | +| 6.1 Co-ordination between B-channel and D-channel ..... | 10 | +| 6.1.1 General ..... | 10 | +| 6.1.2 Outgoing calls ..... | 10 | +| 6.1.3 Incoming calls ..... | 10 | +| 6.1.4 Clearing virtual circuits ..... | 11 | +| 6.1.5 Error handling ..... | 11 | +| 6.2 Layer 2 protocols ..... | 11 | +| 6.2.1 Layer 2 protocol for the D-channel ..... | 11 | +| 6.2.2 Layer 2 protocol for the B-channel ..... | 11 | +| 6.2.2.1 Application rules ..... | 11 | +| 6.2.2.2 Implementation recommendations ..... | 11 | +| 6.3 Layer 3 protocols ..... | 11 | +| 6.3.1 Layer 3 protocol for the D-channel ..... | 11 | +| 6.3.1.1 The access protocol ..... | 11 | +| 6.3.1.2 Terminal addresses ..... | 11 | +| 6.3.1.3 Outgoing calls ..... | 13 | +| 6.3.1.4 Incoming Calls ..... | 14 | +| 6.3.1.5 Release of the switched connection ..... | 15 | +| 6.3.1.6 Supplementary services ..... | 15 | +| 6.3.2 Layer 3 protocol for the B-channel ..... | 15 | +| 6.3.2.1 Bearer Independent Service ..... | 16 | +| 6.3.2.2 Operation over multiple B-channels ..... | 16 | +| 6.3.2.3 DTE role ..... | 16 | +| 6.3.2.4 Logical channels to be used ..... | 16 | +| 6.3.2.5 Packet sizes ..... | 16 | +| 6.3.2.6 Default packet level window size ..... | 16 | +| 6.3.2.7 Default throughput class ..... | 16 | + +| | | | | +|---|----------|-------------------------------------------------------------------------------------|----| +| | 6.3.2.8 | D-bit..... | 16 | +| | 6.3.2.9 | Q-bit..... | 16 | +| | 6.3.2.10 | Protocol identifier ..... | 17 | +| | 6.3.2.11 | Address fields..... | 17 | +| | 6.3.2.12 | Data Link Disconnection Request..... | 17 | +| | 6.3.2.13 | Optional user facilities that shall be supported ..... | 17 | +| | 6.3.2.14 | Recommended optional user facilities and CCITT specified DTE facilities .. | 18 | +| | 6.3.2.15 | Excluded Optional user facilities ..... | 18 | +| 7 | | Access to the ISDN virtual circuit service (X.31 Case B) through the B-channel..... | 19 | +| | 7.1 | Coordination between B-channel and D-channel ..... | 19 | +| | 7.1.1 | General..... | 19 | +| | 7.1.2 | Outgoing calls ..... | 19 | +| | 7.1.3 | Incoming calls..... | 19 | +| | 7.1.4 | Clearing virtual circuits..... | 20 | +| | 7.1.5 | Error handling ..... | 20 | +| | 7.2 | Layer 2 protocols ..... | 20 | +| | 7.2.1 | Layer 2 protocol for the D-channel..... | 20 | +| | 7.2.2 | Layer 2 protocol for the B-channel ..... | 20 | +| | 7.2.2.1 | Application rules..... | 20 | +| | 7.2.2.2 | Implementation recommendations ..... | 20 | +| | 7.3 | Layer 3 protocols ..... | 20 | +| | 7.3.1 | Layer 3 protocol for the D-channel..... | 20 | +| | 7.3.1.1 | The access protocol..... | 20 | +| | 7.3.1.2 | Terminal addresses..... | 20 | +| | 7.3.1.3 | Outgoing calls ..... | 21 | +| | 7.3.1.4 | Incoming calls..... | 22 | +| | 7.3.1.5 | Release of the switched connection ..... | 23 | +| | 7.3.1.6 | Supplementary services..... | 23 | +| | 7.3.2 | Layer 3 protocol for the B-channel ..... | 23 | +| | 7.3.2.1 | Bearer Independent Service ..... | 23 | +| | 7.3.2.2 | Operation over multiple B-channels ..... | 24 | +| | 7.3.2.3 | DTE role ..... | 24 | +| | 7.3.2.4 | Logical channels to be used ..... | 24 | +| | 7.3.2.5 | Packet sizes ..... | 24 | +| | 7.3.2.6 | Default packet level window size ..... | 24 | +| | 7.3.2.7 | Default throughput class ..... | 24 | +| | 7.3.2.8 | D-bit..... | 24 | +| | 7.3.2.9 | Q-bit..... | 24 | +| | 7.3.2.10 | Protocol identifier ..... | 24 | +| | 7.3.2.11 | Address fields..... | 25 | +| | 7.3.2.12 | Data Link Disconnection Request..... | 25 | +| | 7.3.2.13 | Optional user facilities that shall be supported ..... | 25 | +| | 7.3.2.14 | Recommended optional user facilities and CCITT specified DTE facilities .. | 25 | +| | 7.3.2.15 | Excluded optional user facilities ..... | 26 | +| 8 | | Access to the ISDN virtual circuit service (X.31 Case B) through the D-channel..... | 26 | +| | 8.1 | Layer 2 protocol..... | 26 | +| | 8.1.1 | The base Recommendation ..... | 26 | +| | 8.1.2 | Same Connection Endpoint Suffix (CES)..... | 27 | +| | 8.1.3 | Responsibility for Data Link set-up ..... | 27 | + +| | Page | +|---------------------------------------------------------------------------------------------------------------|-------------| +| 8.2 Layer 3 protocols ..... | 27 | +| 8.2.1 General ..... | 27 | +| 8.2.2 Layer 3 ISDN signalling protocols ..... | 27 | +| 8.2.2.1 The base Recommendation ..... | 27 | +| 8.2.2.2 Terminal addresses ..... | 27 | +| 8.2.2.3 Outgoing calls ..... | 27 | +| 8.2.2.4 Incoming calls ..... | 27 | +| 8.2.2.5 Release of the call ..... | 29 | +| 8.2.2.6 Supplementary services ..... | 29 | +| 8.2.3 Layer 3 data communication protocol ..... | 29 | +| 8.2.3.1 Bearer Independent Service ..... | 29 | +| 8.2.3.2 Operation over p-Data Link Connections ..... | 29 | +| 8.2.3.3 DTE role ..... | 29 | +| 8.2.3.4 Logical channels to be used ..... | 29 | +| 8.2.3.5 Packet sizes ..... | 29 | +| 8.2.3.6 Default packet level window size ..... | 29 | +| 8.2.3.7 Default throughput class ..... | 30 | +| 8.2.3.8 D-bit ..... | 30 | +| 8.2.3.9 Q-bit ..... | 30 | +| 8.2.3.10 Protocol identifier ..... | 30 | +| 8.2.3.11 Address fields ..... | 30 | +| 8.2.3.12 Data Link Disconnection Request ..... | 30 | +| 8.2.3.13 Optional user facilities that shall be supported ..... | 30 | +| 8.2.3.14 Recommended optional user facilities and CCITT specified DTE facilities .. | 31 | +| 8.2.3.15 Excluded optional user facilities ..... | 31 | +| Annex A (informative) – ISDN lower layer communication modes for syntax-based Videotex ..... | 32 | +| Annex B (informative) – Overview on communication establishment parameters ..... | 34 | +| B.1 General ..... | 34 | +| B.2 X.25 packet service access ..... | 34 | +| B.2.1 X.25 packet service access parameters ..... | 34 | +| B.2.2 Access of X.25 packet services over the B-channel (X.31 Case A or Case B) ..... | 35 | +| B.2.3 Access of X.25 packet services over the D-channel (X.31 Case B) ..... | 35 | +| B.3 Case selection for communication establishment ..... | 36 | +| B.3.1 Outgoing calls ..... | 36 | +| B.3.2 Incoming calls ..... | 37 | +| Annex C (informative) – End-to-end system configurations ..... | 39 | +| C.1 Introduction ..... | 39 | +| C.2 Network configurations ..... | 39 | +| C.3 Types of interfaces at the two end-systems ..... | 42 | +| C.4 End-system characteristics ..... | 42 | +| Annex D (normative) – Additional provisions for Recommendation X.31 ..... | 43 | +| D.1 General ..... | 43 | +| D.2 Subclause 2.2/X.31: Configuration for the ISDN virtual circuit service (Case B) ..... | 43 | +| D.3 Subclause 3.2.3.2/X.31: Conditional notification class ..... | 44 | +| D.4 Subclause 3.2.3.3/X.31: Unconditional notification class ..... | 44 | +| D.5 Subclause 3.2.3.4/X.31: Information mapping from the X.25 incoming call packet to the Q.931 message ..... | 44 | +| D.6 Subclause 4.1/X.31: Terminal and interface selection ..... | 44 | +| D.7 Subclause 6.1.1/X.31: Circuit-switched access to PSPDN services (Case A) ..... | 44 | +| D.8 Subclause 6.1.2.1/X.31: B-channel ..... | 44 | +| D.9 Subclause 6.2.1.2/X.31: Channel selection ..... | 44 | +| D.10 Subclause 6.2.2.1/X.31: B-channel ..... | 45 | + +| | | | +|---------|---------------------------------------------------------------------------------------|----| +| D.11 | Subclause 6.2.2.3.1/X.31: Channel selection through call offering..... | 45 | +| D.12 | Subclause 6.2.2.3.2/X.31: Information element mapping..... | 45 | +| D.13 | Subclause 6.4.1/X.31: B-channel..... | 45 | +| D.14 | Subclause 7.3.2/X.31: Rate adaption..... | 45 | +| Annex E | (normative) – Additional provisions for Recommendation Q.931 ..... | 46 | +| E.1 | General..... | 46 | +| E.2 | Subclause 2.1.2/Q.931: Network call states ..... | 46 | +| E.3 | Subclause 3.1/Q.931: Messages for circuit mode connection control ..... | 46 | +| E.4 | Subclause 3.1.4/Q.931: CONNECT ..... | 46 | +| E.5 | Subclause 3.1.8/Q.931: Information ..... | 47 | +| E.6 | Subclause 3.1.16/Q.931: Setup..... | 47 | +| E.7 | Subclause 3.2/Q.931: Messages for packet-mode access connection control ..... | 47 | +| E.8 | Subclause 3.4/Q.931: Messages used with the global call reference ..... | 48 | +| E.9 | Subclause 4.3/Q.931: Call reference..... | 48 | +| E.10 | Subclause 4.4/Q.931: Message type ..... | 48 | +| E.11 | Subclause 4.5/Q.931: Other information elements ..... | 48 | +| E.12 | Subclause 4.5.1/Q.931: Coding rules ..... | 48 | +| E.13 | Subclause 4.5.2/Q.931: Extension codesets..... | 49 | +| E.14 | Subclause 4.5.5/Q.931: Bearer capability..... | 49 | +| E.15 | Subclause 4.5.6/Q.931: Call identity ..... | 49 | +| E.16 | Subclause 4.5.7/Q.931: Call state ..... | 49 | +| E.17 | Subclause 4.5.8/Q.931: Called party number ..... | 49 | +| E.18 | Subclause 4.5.9/Q.931: Called party sub-address..... | 49 | +| E.19 | Subclause 4.5.10/Q.931: Calling party number ..... | 49 | +| E.20 | Subclause 4.5.11/Q.931: Calling party sub-address ..... | 49 | +| E.21 | Subclause 4.5.13/Q.931: Channel identification..... | 50 | +| E.22 | Subclause 4.5.15/Q.931: Display..... | 50 | +| E.23 | Subclause 4.5.16/Q.931: High layer compatibility ..... | 50 | +| E.24 | Subclause 4.5.18/Q.931: Low layer compatibility..... | 51 | +| E.25 | Subclause 4.5.21/Q.931: Notification indicator..... | 51 | +| E.26 | Subclause 4.5.23/Q.931: Repeat indicator ..... | 51 | +| E.27 | Subclause 4.5.24/Q.931: Restart indicator..... | 51 | +| E.28 | Subclause 4.7.6/Q.931: Redirecting number ..... | 51 | +| E.29 | Subclause 5.1.1/Q.931: Call request..... | 52 | +| E.30 | Subclause 5.1.2/Q.931: B-channel selection – Originating ..... | 52 | +| E.31 | Subclause 5.1.8/Q.931: Call connected ..... | 52 | +| E.32 | Subclause 5.2/Q.931: Call establishment at the destination interface ..... | 52 | +| E.33 | Subclause 5.2.1/Q.931: Incoming call ..... | 52 | +| E.34 | Subclause 5.2.3.1/Q.931: SETUP message delivered by point-to-point data link..... | 52 | +| E.35 | Subclause 5.2.6/Q.931: Notification of interworking at the terminating interface..... | 52 | +| E.36 | Subclause 5.2.4/Q.931: Overlap receiving ..... | 52 | +| E.37 | Subclause 5.2.7/Q.931: Call accept ..... | 53 | +| E.38 | Subclause 5.3.3/Q.931: Clearing initiated by the user..... | 53 | +| E.39 | Subclause 5.3.4.3/Q.931: Completion of clearing ..... | 53 | +| E.40 | Subclause 5.3.5/Q.931: Clear collision..... | 53 | +| E.41 | Subclause 5.5/Q.931: Restart procedure..... | 53 | +| E.42 | Subclause 5.5.1/Q.931: Sending RESTART ..... | 53 | +| E.43 | Subclause 5.5.2/Q.931: Receipt of RESTART ..... | 53 | +| E.44 | Subclause 5.6/Q.931: Call rearrangements..... | 54 | +| E.45 | Subclauses 5.6.1/Q.931 and 5.6.2/Q.931: Call suspension/suspended ..... | 54 | +| E.46 | Subclause 5.6.3/Q.931: Call suspend error..... | 54 | + +| | Page | +|----------------------------------------------------------------------------------------------------|-------------| +| E.47 Subclause 5.6.4/Q.931: Call re-establishment ..... | 54 | +| E.48 Subclause 5.6.5/Q.931: Call resume errors..... | 54 | +| E.49 Subclause 5.8.3.1/Q.931: Invalid call reference format..... | 54 | +| E.50 Subclause 5.8.3.2/Q.931: Call reference procedural errors ..... | 54 | +| E.51 Subclause 5.8.5/Q.931: General information element errors..... | 54 | +| E.52 Subclause 5.8.7.2/Q.931: Non-mandatory information element content error ..... | 54 | +| E.53 Subclause 5.8.9/Q.931: Data link failure ..... | 55 | +| E.54 Subclause 5.8.10/Q.931: Status enquiry procedure ..... | 55 | +| E.55 Annex B/Q.931: Compatibility checking ..... | 55 | +| Annex F (normative) – Information elements for the control of packet-mode access connections ..... | 55 | +| F.1 Protocol discriminator..... | 55 | +| F.2 Call reference..... | 55 | +| F.3 Message type ..... | 56 | +| F.4 Other information elements ..... | 56 | +| F.6 Redirecting number ..... | 57 | +| Annex G (informative) – References..... | 60 | + + + +# SYNTAX-BASED VIDEOTEX END-TO-END PROTOCOLS FOR THE PACKET MODE ISDN + +(Helsinki, 1993) + +# 1 Scope + +This Recommendation specifies the usage of all protocols and supplementary services up to and including layer 3 for syntax-based Videotex terminal equipment in the ISDN. The scope of this Recommendation is limited to virtual circuits using the three different DTE/DCE modes of connection. i.e.: + +- a) the DTE/DCE connection to PSPDN services (X.31 Case A); +- b) the ISDN virtual circuit service through the B-channel (X.31 Case B); +- c) the ISDN virtual circuit service through the D-channel (X.31 Case B). + +This Recommendation is applicable to terminal equipment supporting the syntax-based Videotex using either basic access or primary rate access to the ISDN. In this context, a terminal equipment is either a Videotex Terminal, a Videotex Service Centre, a Videotex Access Point or a Videotex Host (see 3. 1). + +This Recommendation is based on other CCITT Recommendations or International Standards, and where necessary, it adds new or other requirements as application rules. + +# 2 Normative references + +- [1] CCITT Recommendation F.300 (1988), *Videotex Service*. +- [2] CCITT Recommendation I.333 (1988), *Terminal Selection Functions in ISDN*. +- [3] CCITT Recommendation I.430 (1988), *Integrated Services Digital Network (ISDN) – Basic user-network interface, Layer 1 specification*. +- [4] CCITT Recommendation I.431 (1988), *Integrated Services Digital Network (ISDN) – Primary rate user-network interface, Layer 1 specification*. +- [5] CCITT Recommendation T.105 (1993), *Syntax-based Videotex application layer protocol*. +- [6] CCITT Recommendation Q.921 (1988), *Integrated Services Digital Network (ISDN) – User-network interface data link layer specification*. +- [7] CCITT Recommendation 0.931 (1988), *Integrated Services Digital Network (ISDN) – User-network interface layer 3, Specification for basic call control*. +- [8] CCITT Recommendation X.25 (1988), *Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and connected to public data network by dedicated circuit*. +- [9] CCITT Recommendation X.31 (1988), *Support of packet mode terminal equipment by an ISDN*. +- [10] CCITT Recommendation X.32 (1988), *Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and accessing a packet switched public data network through a public switched telephone network or an integrated services digital network or a circuit switched public data network*. +- [11] ISO 7498:1984, *Information processing systems – Open Systems Interconnection – Basic Reference Model*. +- [12] ISO 7776:1986, *Information processing systems – Data communications – High-level data link control procedures – Description of the X.25 LAPB-compatible DTE data link procedures*. + +- [13] ISO/IEC 8208:1990, *Information technology – Data communications – X.25 Packet Layer Protocol for Data Terminal equipment*. +- [14] ISO 8509:1987, *Information processing systems – Open Systems interconnection – Service Conventions*. +- [15] ISO/IEC TR 9577:1990, *Information technology – Telecommunications and information exchange between systems – Protocol identification in the network layer*. + +# 3 Definitions and abbreviations + +## 3.1 Definitions + +For the purposes of this Recommendation, the following definitions apply: + +**access function:** The functional entity which gives access to the Videotex Service. This entity is an integral part of the Videotex Service. + +**access network:** The network which provides the link between the Terminal Function and the Access Function. + +**bearer independent service access point:** Point in an end system where the user of the Bearer Independent Service accesses the service. + +**called BIS user:** A BIS user with whom a calling BIS user wishes to establish a Network Connection. + +**calling BIS user:** A BIS user that initiates a Network Connection establishment request. + +**data circuit-terminating-equipment:** See ISO/IEC8208 [13] and CCITT Recommendation X.25 [8]. + +**data terminal equipment:** See ISO/IEC 8208 [13] and CCITT Recommendation X.25 [8]. + +**host function:** The abstraction of the Videotex Applications available in a particular Videotex Service. + +**logical channel:** See ISO/IEC 8208 [13] and CCITT Recommendation X.25 [8]. + +**network connection:** See OSI Reference Model ISO 7498 [11]. + +**network layer:** See OSI Reference Model ISO 7498 [11]. + +**network service:** See OSI Reference Model ISO 7498 [11]. + +**packet layer:** See ISO/IEC 8208 [13] and CCITT Recommendation X.25 [8]. + +**primitive:** See Service Conventions Standard ISO/TR 8509 [14]. + +**terminal function:** The abstraction of a functional entity which acts as a Videotex Terminal. + +**videotex access point:** See CCITT Recommendation F.300 [1]. + +**videotex host:** This term describes a computer which offers one or more applications and/or facilities. It can be represented through a Videotex Host Computer, an External Videotex Host or a Videotex Service Centre. + +**videotex host computer:** See CCITT Recommendation F.300 [1]. + +**videotex service:** See CCITT Recommendation F.300 [1]. + +**videotex service centre:** See CCITT Recommendation F.300 [1]. + +NOTE – According to CCITT Recommendation F.300, a Videotex Service Centre provides host and/or access functions, i.e. it may also act as a Videotex Access Point. + +**videotex terminal:** See CCITT Recommendation F.300 [1]. + +**virtual call:** See ISO/IEC 8208 [13] and CCITT Recommendation X.25 [8]. + +**virtual circuit:** See ISO/IEC 8208 [13] and CCITT Recommendation X.25 [8]. + +## 3.2 Abbreviations + +For the purposes of this Recommendation, the following abbreviations apply: + +| | | +|-------|--------------------------------------------------------------| +| AU | Access Unit | +| BC | Bearer Capability | +| BIS | Bearer Independent Service | +| CCITT | International Telegraph and Telephone Consultative Committee | +| CES | Connection Endpoint Suffix | +| D-bit | Delivery Confirmation bit | +| DCE | Data Circuit-terminating Equipment | +| DDI | Direct-Dialling-In | +| DTE | Data Terminal Equipment | +| DXE | either a DTE or a DCE | +| ETS | European Telecommunication Standard | +| HLC | High Layer Compatibility | +| ISDN | Integrated Services Digital Network | +| ISO | International Organization for Standardization | +| LLC | Low Layer Compatibility | +| M-bit | More Data bit | +| MSN | Multiple Subscriber Number | +| NL | Network Layer | +| NS | Network Service | +| OSI | Open Systems Interconnection | +| PABX | Private Automatic Branch eXchange | +| PDN | Public Data Network | +| PH | Packet Handler | +| PLP | Packet Level Protocol | +| PSPDN | Packet Switched PDN | +| PSTN | Public Switched Telephone Network | +| PVC | Permanent Virtual Circuit | +| Q-bit | Qualifier bit | +| SBV | Syntax-Based Videotex | +| SUB | Sub-addressing | +| TP | Terminal Portability | +| UUS | User-to-User Signalling | +| VC | Virtual Call | + +# 4 Introduction + +## 4.1 General + +The following subclauses specify the additional requirements to those as specified in Recommendation T. 105 [5] to provide the Bearer Independent Service for syntax-based Videotex (SBV BIS) + +ISDN end-systems conforming to this Recommendation present protocol stacks at the S- or T-reference point as indicated in 4.3. Only virtual circuit services are within the scope of this Recommendation. + +For outgoing calls, the requirements of 6.1/X.31 [9] shall apply. + +For incoming calls, the requirements of 6.2/X.31 [9] shall apply + +The following subclauses consider the different cases of X.25 packet service access types (i.e. X.31 [9] case A, X.31 [9] case B, B-channel or D-channel). + +### NOTES + +1 Annex A (informative) gives an overview of all the different possible communication modes in an ISDN. + +2 Annex B (informative) summarises possibilities for accessing the X.25 [8] packet services at the S/T reference point and gives the different parameters for case selection. + +3 This Recommendation makes reference to Recommendations X.31 [9] and Q.931 [7]. Additional provisions in the context of this Recommendation are given in normative Annexes D and E, respectively. + +4 In the following subclauses, the term “Semi-permanent” refers to both of the two access types as defined in clause 6/X.31 [9]. + +### 4.1.1 X.31 Case A access + +For the X.31 Case A “Switched” access of the B-channel, the requirements of clauses 5 (Layer 1) and 6 shall apply. + +For the X.31 Case A “Semi-permanent access of the B-channel, the requirements of clause 5 (Layer 1) and of 6.1.5 (error handling), 6.2.2 (Layer 2 of the B-channel) and 6.3.2 (Layer 3 of the B-channel) shall apply. + +### 4.1.2 X.31 Case B, B-channel access + +For the X.31 Case B “Switched” access of the B-channel, the requirements of clauses 5 (Layer 1) and 7 shall apply. + +For the X-31 Case B “Semi-permanent” access of the B-channel, the requirements of clause 5 (Layer 1) and of 7.1.5 (error handling), 7.2.2 (Layer 2 of the B-channel) and 7.3.2 (Layer 3 of the B-channel) shall apply. + +### 4.1.3 X.31 Case B, D-channel access + +The requirements of clauses 5 (Layer 1) and 8 shall apply, except that 8.2.2.4 (incoming calls) shall not be applicable if the “No notification” class is used. + +## 4.2 Reference Configurations + +This subclause illustrates the different scenarios as covered by this Recommendation. For a clarification of the resulting possible end-to-end configurations refer to Annex C (informative). + +### 4.2.1 Using access to PSPDN services (X.31 Case A) + +Figure 1 illustrates the scenario for the access via an access unit (AU) to a PSPDN which is conceptually not a part of the ISDN. For a detailed description refer to 2.1/X.31 [9], “Configuration when accessing PSPDN services”. + +### 4.2.2 Using the ISDN virtual circuit service (X.31 Case B) through the B-channel or the D-channel + +Figure 2 shows the scenario for the case that a packet handler (PH) is an integral part of the ISDN. For a detailed description refer to 2.2/X.31 [9], “Configuration for the ISDN virtual circuit service”. + +## 4.3 Protocol Pillars + +### 4.3.1 Using access to PSPDN services (X.31 Case A) + +The protocol pillar in Figure 3 is applicable for the access to PSPDN services: + +![Diagram of ISDN configuration based on X.31 [9], Case A. Two ISDN SBVTs connect via S/T reference points to NT units. These connect to an ISDN cloud containing ET units. The ISDN cloud connects to a PSPDN cloud via AU ports. One path shows a direct connection through ETs, another shows a connection through an ET to an AU. A cross symbol indicates a connection point within the ISDN cloud.](af7916c89a458fdab6c3f443217388ae_img.jpg) + +``` + +graph LR + subgraph User_Side_1 + SBVT1[ISDN SBVT] -- S/T --- NT1[NT] + end + subgraph User_Side_2 + SBVT2[ISDN SBVT] -- S/T --- NT2[NT] + end + subgraph ISDN_Network[ISDN] + NT1 --- ET1[ET] + NT2 --- ET3[ET] + ET1 --- X((X)) --- ET2[ET] + end + subgraph PSPDN_Network[PSPDN] + ET2 --- AU1[AU] + ET3 --- AU2[AU] + end + +``` + +ISDN + +T0818410-94/d01 + +Diagram of ISDN configuration based on X.31 [9], Case A. Two ISDN SBVTs connect via S/T reference points to NT units. These connect to an ISDN cloud containing ET units. The ISDN cloud connects to a PSPDN cloud via AU ports. One path shows a direct connection through ETs, another shows a connection through an ET to an AU. A cross symbol indicates a connection point within the ISDN cloud. + +— B-channel is used +S/T Coincident S- and T-reference point +NT Network termination +ET Exchange termination +AU ISDN access unit ports +SBVT Syntax-based Videotex terminal + +NOTE – This figure is only an example of many possible configurations and is included as an aid to the text describing the various interface configuration. + +FIGURE 1/T.103 +**Configuration based on X.31 [9], Case A** + +![Diagram of ISDN configuration based on X.31 [9], Case B. Two ISDN SBVT terminals connect to NT blocks via S/T interfaces. These connect to an ISDN network containing ET and PH blocks. The ISDN network connects to a PSPDN and another ISDN network. Solid lines represent B-channels, and dashed lines represent D-channel or B-channel usage.](4801720824e4b5e2361a5564f91cfb70_img.jpg) + +B-channel is used + D-channel or B-channel is used + S\T Coincident S- and T-reference point + NT Network termination + ET Exchange termination + PH ISDN packet handling function + SBVT Syntax-based Videotex terminal + +NOTES + +- 1 This figure is only an example of many possible configurations and is included as an aid to the text describing the various interface configurations. +- 2 For access over the D-channel, this connection is either on demand or semi-permanent. This fact has no relevance for the user-network procedures. +- 3 In some implementations, the PH belonging to the ISDN may reside physically in a node of the PSPDN. The service provided is still the ISDN virtual circuit service. + +T0818420-94/d02 + +Diagram of ISDN configuration based on X.31 [9], Case B. Two ISDN SBVT terminals connect to NT blocks via S/T interfaces. These connect to an ISDN network containing ET and PH blocks. The ISDN network connects to a PSPDN and another ISDN network. Solid lines represent B-channels, and dashed lines represent D-channel or B-channel usage. + +FIGURE 2/T.103 +**Configuration based on X.31 [9], Case B** + +| | | | +|-------|---------------------------|---------------------------------------------------------| +| 3 | Coordination (Note 1) | | +| | BIS (Note 2) | | +| | Q.931 [7] | ISO/IEC 8208 [13]
(X.25 PLP for DTE/DCE)
(Note 3) | +| 2 | Q.921 [6] | ISO 7776 [12]
(X.25 LAPB for DTE/DCE)
(Note 4) | +| 1 | I.431 [4] or
I.430 [3] | | +| Layer | D-channel | B-channel | + +#### NOTES + +1 The coordination function specifies the relationship between D-channel and B-channel protocol pillars and is consistent with Recommendation X.31 [9]. + +2 The syntax-based Videotex Bearer Independent Service (SBV BIS) is defined in clause 11/T.105 [5]. It covers also some aspects of the out-band signalling procedures. + +3 CCITT Rec. X.25 [8] PLP may also be taken as the base Recommendation. However, only ISO/IEC 8208 [13] is referred to explicitly throughout this Recommendation. + +4 CCITT Rec. X.25 [8] LAPB may also be taken as the base Recommendation. However, only ISO 7776 [12] is referred to explicitly throughout this Recommendation. + +FIGURE 3/T.103 + +#### Protocol pillar for the DTE/DCE connection to PSPDN services (X.31 [9] Case A) + +At layer 1, Recommendation I.430 [3] is used for ISDN basic access and Recommendation I.431 [4] is used for ISDN primary rate access. At layer 2, CCITT Rec. Q.921 [6] provides for the LAPD Data link procedures on the D-channel and ISO 7776 [12] provides for the LAPB Data link procedures on the B-channel (additional application rules are given in 6.2) At layer 3, CCITT Rec. Q.931 [7] signalling procedures are used on the D-channel, and ISO/IEC 8208 [13] packet level protocol is used in DTE/DCE operation on the B-channel (additional application rules are given in 6.3). + +The provisions of the SBV BIS as defined in clause 11/CCITT Rec. T.105 [5] apply with regard to the mappings of the BIS primitives and parameters to and from the elements of the ISO/IEC 8208 [13] packet level protocol. + +### 4.3.2 Using the ISDN virtual circuit service (X.31 Case B) through the B-channel + +The protocol pillar in Figure 4 is applicable for an access using ISDN virtual circuit services over the B-channel. + +| | | | +|-------|---------------------------|---------------------------------------------------------| +| 3 | Coordination (Note 1) | | +| | BIS (Note 2) | | +| | Q.931 [7] | ISO/IEC 8208 [13]
(X.25 PLP for DTE/DCE)
(Note 3) | +| 2 | Q.921 [6] | ISO 7776 [12]
(X.25 LAPB for DTE/DCE)
(Note 4) | +| 1 | I.431 [4] or
I.430 [3] | | +| Layer | D-channel | B-channel | + +#### NOTES + +1 The coordination function specifies the relationship between D-channel and B-channel protocol pillars and is consistent with Recommendation X.31 [9]. + +2 The syntax-based Videotex Bearer Independent Service (SBV BIS) is defined in clause 11 of Recommendation T.105 [5]. It covers also some aspects of the out-band signalling procedures. + +3 CCITT Rec. X.25 [8] PLP may also be taken as the base Recommendation. However, only ISO/IEC 8208 [13] is referred to explicitly throughout this Recommendation. + +4 CCITT Rec. X.25 [8] LAPB may also be taken as the base Recommendation. However, only ISO 7776 [12] is referred to explicitly throughout this Recommendation. + +FIGURE 4/T.103 + +#### Protocol pillar for the DTE/DCE connection using the ISDN virtual circuit service through the B-channel (X.31 [9] Case B) + +At layer 1, Recommendation I.430 [3] is used for ISDN basic access and Recommendation I.431 [4] is used for ISDN primary rate access. At layer 2, CCITT Rec. Q.921 [6] provides for the LAPD Data link procedures on the D-channel and ISO 7776 [12] provides for the LAPB Data link procedures on the B-channel (additional application rules are given in 7.2). At layer 3, CCITT Rec. Q.931 [7] signalling procedures are used on the D-channel, and ISO/IEC 8208 [13] packet level protocol is used in DTE/DCE operation on the B-channel (additional application rules are given in 7.3). + +The provisions of the SBV BIS as defined in clause 11/CCITT Rec. T.105 [5] apply with regard to the mappings of the BIS primitives and parameters to and from the elements of the ISO/IEC 8208 [13] packet level protocol. + +### 4.3.3 Using the ISDN virtual circuit service (X.31 Case B) through the D-channel + +The protocol pillar in Figure 5 is applicable for an access using ISDN virtual circuit services over the D-channel. + +| 3 | Coordination (Note 1) | | +|-------|---------------------------|---------------------------------------------------------| +| | BIS (Note 2) | | +| | Q.931 [7]
(Note 3) | ISO/IEC 8208 [13]
(X.25 PLP for DTE/DCE)
(Note 4) | +| 2 | Q.921 [6] | | +| 1 | I.431 [4] or
I.430 [3] | | +| Layer | D-channel | | + +#### NOTES + +1 The coordination function specifies the relationship between the two layer 3 protocol pillars and is consistent with Recommendation X.31 [9]. + +2 The syntax-based Videotex Bearer Independent Service (SBV BIS) is defined in clause 11/T.105 [5]. It covers also some aspects of the out-band signalling procedures. + +3 Recommendation Q.931 [7] is applicable for incoming calls. + +4 CCITT Rec. X.25 [8] PLP may also be taken as the base Recommendation. However, only ISO/IEC 8208 [13] is referred to explicitly throughout this Recommendation. + +FIGURE 5/T.103 + +#### Protocol pillar for the DTE/DCE connection using the ISDN virtual circuit service through the D-channel (X.31 [9] Case B) + +At layer 1, Recommendation I.430 [3] is used for ISDN basic access and Recommendation I.431 [4] is used for ISDN primary rate access. At layer 2, Rec. Q 921 [6] provides for the LAPD Data link procedures on the D-channel (additional application rules are given in 8.1). At layer 3, ISO/IEC 8208 [13] packet level protocol is used in DTE/DCE operation (additional application rules are given in 8.2.3). In addition, CCITT Rec. Q.931 [7] is used for the notification of incoming calls (additional application rules are given in 8.2.2). + +The provisions of the SBV BIS as defined in clause 11/CCITT Rec. T.105 [5] apply with regard to the mappings of the BIS primitives and parameters to and from the elements of the ISO/IEC 8208 [13] packet level protocol. + +## 5 Layer 1 + +### 5.1 Basic access + +For terminals using the basic access to an ISDN, Recommendation I.430 [3] is applicable without any additional rule + +## **5.2 Primary rate access** + +For terminals using the primary rate access to an ISDN, Recommendation I.431 [4] is applicable without any additional rule. + +## **6 Access to PSPDN services (X.31 Case A)** + +### **6.1 Co-ordination between B-channel and D-channel** + +#### **6.1.1 General** + +ISDN Videotex end-systems supporting access to PSPDN services over the B-channel (X.31 [9] Case A) shall use a protocol stack at the S- or T- reference point in accordance with the standards as indicated in Figure 3 (see 4.3.1). + +One stack is used to support signalling on the D-channel for circuit switched access to the access unit function (AU) of the PSPDN. In the case of the semi-permanent B-channel service, this stack is null. The other stack is used to support packet switched signalling and information transfer. The detailed protocols are given in 6.2.2 and 6.3.2. + +Clause 11/CCITT Rec. T.105 [5] provides the definition of a Bearer Independent Service for syntax-based Videotex (SBV BIS) and the mapping of its elements to the protocol and procedures of ISO/IEC 8208 [13]. Additional requirements for calls originated by or directed toward the ISDN end-system are specified below. Co-ordination is only required for switched B-channel ISDN connections between the end-system and the AU. + +#### **6.1.2 Outgoing calls** + +Additional procedures are required if a B-channel is not already established or if an additional B-channel is needed to support the additional traffic. + +The reception by layer 3 of a BIS-N-CONNECT request primitive shall first cause the ISDN D-channel signalling procedure for demand access to be used to establish a B-channel as indicated in 6.3. + +NOTE 1 The “Called party number” information element of the SETUP message as defined in Recommendation Q.931 [7] contains the ISDN address of the PSPDN Access Unit. The determination of the contents of this information element, and its derivation from the “Called Address” parameter of the BIS-N-CONNECT primitive are a local matter. + +After a successful establishment of this B-channel connection, the procedures of clause 11/T.105 [5] shall apply. + +NOTE 2 – The called address in the X.25 CALL REQUEST packet (derived from the BIS-N-CONNECT request primitive) is used for routing from the AU through the Access Network to the Access Function. + +Failure to establish the B-channel connection is indicated to the BIS user by means of a BIS-N-DISCONNECT indication primitive with the originator parameter indicating “ISDN” and the reason parameter filled as indicated in 6.1.5. + +#### **6.1.3 Incoming calls** + +For the “No notification” class, no additional procedures are required. + +If an ISDN end-system interface has subscribed to the “Conditional notification” class, and the AU needs to establish a B-channel (first B-channel or additional B-channel) for the incoming call packet which it has to send to this ISDN packet mode end-system, the following additional procedures are required. + +The attempt to establish a B-channel will cause the ISDN call offering procedures to be used at the ISDN end-system interfaces, as described in 6.3.1.4 and in 6.2.1.2/X.31 [9]. These procedures may offer the called ISDN end-system to determine which idle B-channel is to be used. These procedures are not visible to the BIS user (i.e. no BIS primitive will be issued to this BIS user). + +After the successful establishment of this B-channel connection, the procedures specified in 6.2.2 and 6.3.2 and clause 11/T.105 [5] shall apply. + +#### **6.1.4 Clearing virtual circuits** + +It is recommended that the NL entity starts a timer T320 (see Recommendation Q.931 [7]) after the last SBV Network Connection has been released. This timer is cleared upon establishment of the next virtual circuit. Upon expiry of T320, clearing of the B-channel should be initiated. + +These procedures are not visible to the BIS user. + +#### **6.1.5 Error handling** + +If one or more SBV Network Connections are established or in the process of being established on an established B-channel and that B-channel is disconnected, this disconnection shall be indicated to the BIS user by means of a BIS-N-DISCONNECT indication primitive with the originator parameter indicating "ISDN". + +The reason parameter for each of the SBV Network Connections established or in the process of being established is equal to Recommendation Q.931 [7] cause of the related clearing message. In case of the transmission or the receipt of a RESTART message, the reason parameter indicates "Temporary failure" (cause #41). + +### **6.2 Layer 2 protocols** + +#### **6.2.1 Layer 2 protocol for the D-channel** + +The base Recommendation for the layer 2 protocol of the D-channel is Recommendation Q.921 [6]. The provision of Recommendation Q.921 [6] applicable to Data Link Connections between SAPs used for call control procedures (SAPI = 0) are valid without further application rules. + +NOTE – The D-channel protocol is only applicable to switched ISDN connections between the terminal and the AU. + +#### **6.2.2 Layer 2 protocol for the B-channel** + +The base Recommendation for the layer 2 protocol of the B-channel is ISO 7776 [12]. The conformance requirements for the Data Link Layer in the B-channel shall be in accordance with the base Recommendation with respect to DTE/DCE operation and with CCITT Rec. X.32 [10], subject to the provisions as detailed in the remainder of this subclause. + +NOTE – CCITT Rec. X.25 [8] LAPB may also be taken as base Recommendation, however explicit references to subclauses are only made with respect to ISO 7776 [12] in this Recommendation. + +##### **6.2.2.1 Application rules** + +The application rules of Table I shall apply. + +##### **6.2.2.2 Implementation recommendations** + +The implementation recommendations for layer 2 of the channel are contained in Table 2. + +### **6.3 Layer 3 protocols** + +#### **6.3.1 Layer 3 protocol for the D-channel** + +##### **6.3.1.1 The access protocol** + +The base Recommendation for the layer 3 protocol of the D-channel is Recommendation Q.931 [7]. The requirements of the base Recommendation shall apply, subject to the provisions of Recommendation X.31 [9] (as far as applicable to terminals accessing the PSPDN service), and subject to the provisions of the subsequent subclauses. + +NOTE – The D-channel protocol is only applicable to switched ISDN connections between the terminal and the AU. + +##### **6.3.1.2 Terminal addresses** + +Subclause 4.1/X-31 [9] shall apply. For the use of addressing supplementary services, see 6.3.1.6 below. + +TABLE 1/T.103 + +**Application rules for B-channel layer 2** + +| Case | Item | Application Rule | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| a | Single link procedure | Only the single link procedure shall be supported. | +| b | Independence of LAPB protocols | An independent LAPB protocol shall operate over each B-channel. | +| c | Data Link set-up | The responsibility for Data Link setup depends on the notification class and on other agreements with the network provider. Table B.1 (informative) shows the different possibilities. | +| d | Maximum frame length NI | Parameter NI (maximum number of bits in an I-frame) shall be such that the Data Link layer is capable of carrying the maximum packet size negotiated at the packet level, plus the related packet level and Data Link level control information. Guidance on the derivation of the value of NI can be found in Appendix II/X.25 [8]. | +| e | Link set-up in FRMR condition | The DTE shall support the procedure of transmitting an FRMR response frame up to N2 times, if necessary, in order to get the DCE to reset the link. | +| f | Address assignment | The Data Link Layer address assignment shall be according to one of the methods described in 5.2/X.32 [10]. | +| g | Modes of operation | Basic (module 8) operation shall be supported. Extended mode of operation (module 128) may be supported in addition. | +| h | Default window size k | The default window sizes shall be:
7 for basic mode of operation;
80 for extended mode of operation. | +| i | Selection of mode of operation and window size | In case of demand access of the PSPDN:

If no negotiation of the mode of operation is performed, the basic mode shall be used. If no negotiation of the window size k is performed, the default window size shall be taken.

The use of out-band signalling employing LLC information elements to negotiate the mode of operation and/or window size is for further study.

The use of XID procedures to negotiate the mode of operation and/or window size is for further study.

In case of semi-permanent access of PSPDN:

Operational agreements between the user and the provider of the PSPDN services apply. | +| j | Disconnection order | In the normal procedure for disconnection, the Data Link shall be disconnected before disconnecting the B-channel. | +| k | Identification | When an exchange of identification information between DTE and DCE is needed, the method of exchange shall be one of the methods given in X.32 [10]. The requirements of the PSPDN govern which method is used. | +|

NOTES

1 The different draft functional standards specify the use of basic mode. However, extended mode is not ruled out explicitly and is for further study.

2 Recommendation T.90 (1992) specifies procedures for B-channel negotiation of layer 2 parameters using the "Exchange Identification (XID) Frame" mechanism. The use of this is for further study.

| | | + +TABLE 2/T.103 + +**Implementation recommendations for B-channel layer 2** + +| Case | Item | Implementation recommendations | +|------|-------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| a | Address assignment | It is strongly recommended, that both methods of Data Link Layer address assignment, as described in 5.2/X.32 [10], are implemented. Which method is used, depends on the operational requirements of the PSPDN. | +| b | Parameter N2 | For parameter N2 (maximum number of attempts) the value 10 is recommended. | +| c | Timer T1 | It is recommended that the value of Timer T1 (retransmission) is tuneable in the range from 100 ms to 15 s. | +| d | I-frame acknowledgement | It is recommended that an RR frame be used as an acknowledgement of received I-frames, unless an outgoing I-frame is available. | +| e | Timer T3 | It implemented Timer T3 (disconnected) is recommended to be greater than or equal to $T1 \times 10$ . | +| f | Timer T4 | It is recommended to implement Timer T4. | + +**6.3.1.3 Outgoing calls** + +The requirements of 4.2 and 6.1.1/X.31 [9] apply without modification. + +The Bearer Capability information element shall be coded as indicated in Table 3. Fields not shown in the table shall be omitted. + +TABLE 3/T.103 + +**Coding of the Bearer Capability information element** + +| Octets | Information element field | Field value | +|--------|-------------------------------------------|----------------------------------| +| 1 | Information element identifier | Bearer capability | +| 2 | Length of contents of information element | 00000010 | +| 3 | Coding standard | CCITT standardized coding | +| | Information transfer capability | Unrestricted digital information | +| 4 | Transfer mode | Circuit mode | +| | Information transfer rate | 64 kbit/s | + +The Low Layer Compatibility information element shall be coded as indicated in Table 4. Fields not shown in the table shall be omitted. + +The High Layer Compatibility information element shall not be included in the SETUP message. + +TABLE 4/T.103 + +**Coding of the Low Layer Compatibility information element** + +| Octets | Information element field | Field value | +|---------------------------------------------------------------------------------------------------|-------------------------------------------|-----------------------------------------------------------------| +| 1 | Information element identifier | Low layer compatibility | +| 2 | Length of contents of information element | 00000101 | +| 3 | Coding standard | CCITT standardized coding | +| | Information transfer capability | Unrestricted digital information | +| 4 | Transfer mode | Circuit mode | +| | Information transfer rate | 64 kbit/s | +| 5 | User information layer 1 protocol | CCITT standardized rate adaption X.31 HDLC flag stuffing (Note) | +| 6 | User information layer 2 protocol | Recommendation X.25, link layer | +| 7 | User information layer 3 protocol | Recommendation X.25, packet layer | +| NOTE – Octet 5 is not mandatory in Recommendation T.90. When used, it should be coded like above. | | | + +**6.3.1.4 Incoming Calls** + +To select a called terminal correctly, the terminal(s) at the user/network interface will be served with information generated by the calling terminal and the intermediate network(s). + +Annex B/Q.931 [7], specifies the procedure of compatibility checking as part of the access protocol. The information elements to be considered are those containing address information, the Bearer Capability information element and the Low Layer Compatibility information element. + +The requirements of Annex B/Q.931 [7] shall apply. The following rules specify further details on terminal selection and compatibility checking and add requirements for Syntax-based Videotex terminals. + +The result of this procedure is to decide whether to ignore, to reject or to accept the incoming call. + +a) *B.3.1/Q.931 [7]* + +It a call is offered with address information, this information shall be checked against the local address before network-to-user and user-to-user compatibility checking. In this context, Note 1 in B.3.1/Q.931 [7] is not applicable. + +In case of mismatch of any presented address information, no further compatibility checking is required and the call shall be ignored. + +If no address information is offered, or the offered address information is not complete with respect to the local address (e.g. because the Sub-addressing supplementary service is subscribed, but the called sub-address is not offered), the terminal shall continue with network-to-user and user-to-user compatibility checking. It is not allowed to ignore a call for missing address information only. + +b) *B.3.2/Q.931 [7]* + +A terminal matches the received network-to-user information, if the information in the received Bearer Capability information element offered in the SETUP message is exactly as specified in Table 3 (i.e. fields not indicated in this table shall not be present). + +It a mismatch is detected while checking the Bearer Capability information element, the terminal shall reject the call in accordance to 5.2.5.1/Q.931 [7]. It is not permitted to ignore the call. + +c) *B.3.3/Q.931 [7]* + +All offered user-to-user compatibility information shall be checked. + +The user-to-user compatibility information may not be presented in some interworking cases with certain ISDNs and non-ISDNs. Not all of these interworking cases will be indicated by means of a progress indicator information element. Therefore a terminal need not reject an incoming call due to missing user-to-user information elements, independently of the information possibly provided by progress indicators. + +If user-to-user compatibility information (contained in the LLC information element) is offered in the SETUP message, a terminal matches this information if this information is as specified in Table 4. + +If the user-to-user compatibility information is not offered or not offered completely, a terminal may act as a compatible terminal independently of whether the progress indicator is present or not. + +If a mismatch is detected, the terminal shall reject the call in accordance to 5.2.5.1/Q.931 [7]. It is not permitted to ignore the call. + +d) *B.3.4/Q.931 [7]* + +This subclause requires user actions to be carried out as result of compatibility checking. It is superseded by this Recommendation. + +If a terminal has not rejected or ignored the call while following the procedures a), b), c) and d), it shall accept the call or reject it for other reasons (see below). + +If a terminal is obliged to reject the call while following the procedures a) to d), the cause code to be used is defined in B.3/Q.931 [7]. + +If a terminal rejects the call for different reasons, it should indicate a cause from the following list: + +- a) cause code # 17: User busy (already involved in another call); +- b) cause code #47: Resources unavailable, unspecified; +- c) cause code #21: Call rejected (e.g., other local reasons apply). + +If the terminal accepts the incoming call, the co-ordination function initiates the appropriate Link Layer and Network Layer functions in the channel as detailed in 6. 1. + +#### **6.3.1.5 Release of the switched connection** + +Subclause 6.4.1/X.31 [9] applies, however the terminal shall not release the switched connection while a virtual call is established or in the process of being established over the related B-channel. + +NOTE – Further requirements on handling of failures or premature clearing of the switched connection can be found in the description of the co-ordination function in 6.1. + +#### **6.3.1.6 Supplementary services** + +The use of supplementary services of a specific ISDN depends on provisions and requirements of the network. + +The procedures for UUS are specified in Recommendation Q.931 [7]. + +The addressing supplementary services: DDI (Direct-Dialling-In), MSN (Multiple Subscriber Number) or SUB (Sub-addressing), or a combination of them, may be useful or even required by the network, if multiple terminals have been attached to the same ISDN address. + +The TP (Terminal Portability) supplementary service shall not be used. + +#### **6.3.2 Layer 3 protocol for the B-channel** + +The base Recommendation for the Network Layer in the B-channel is ISO/IEC 8208 [13]. The conformance requirements for the Network Layer in the channel shall be in accordance with the base Recommendation with respect to DTE/DCE operation and with CCITT Rec. X.32 [10], subject to the additional requirements as detailed in the remainder of this subclause. + +NOTE – Rec. X.25 [8] PLP may also be taken as base Recommendation, however explicit references to subclauses are only made with respect to ISO/IEC 8208 [13] in this Recommendation. + +#### **6.3.2.1 Bearer Independent Service** + +The service that the Network Layer entity provides to the Videotex application with respect to setup, clear, reset of Network Connections and data transfer over established Network Connections, shall be as described in clause 11/T.105 [5]. + +#### **6.3.2.2 Operation over multiple B-channels** + +If a terminal operates more than one B-channel, the Network Layer of each B-channel connection shall be processed independently from the Network Layer of each other B-channel connection. + +#### **6.3.2.3 DTE role** + +The Network Layer entity shall adopt the role of a DTE. + +#### **6.3.2.4 Logical channels to be used** + +The logical channel ranges (LIC, HIC, LTC, HTC, LOC and HOC) to be used are determined by local knowledge. If local knowledge is not available, then by default only a single two-way logical channel shall be used. (i.e. LTC and HTC will be set to 1, while LIC, HIC, LOC and HOC shall be set to zero). If more than one logical channel is available, a higher value of HTC may be negotiated using the On-line Facility Registration facility. + +If a DTE is capable of initiating a REGISTRATION request packet, then the registration parameters shall be set as follows: + +- The LIC, HIC, LOC and HOC parameter shall be set to zero. The LTC shall be set to the value of 1. The value in the “total number of logical channels” parameter field shall be set equal to the value in the HTC parameter field. + +#### **6.3.2.5 Packet sizes** + +The Network Layer entity shall be capable of supporting the standard default packet size of 128 octets. The only permitted maximum data packet sizes are 128, 256, 512, 1024 and 2048 octets. Packet sizes other than the standard default packet size may be negotiated on a per call basis using the “Flow Control Parameter Negotiation” facility. + +#### **6.3.2.6 Default packet level window size** + +The Network Layer entity shall be capable of supporting the standard default window size of 2. Other window sizes may be negotiated on a per call basis using the “Flow Control Parameter Negotiation” facility. + +#### **6.3.2.7 Default throughput class** + +The default throughput class assigned to each direction of transmission shall be 64 kbit/s. Other default throughput class values may be agreed on a subscription basis. Other throughput classes may be negotiated on a per call basis using the “Throughput Class Negotiation” facility. + +#### **6.3.2.8 D-bit** + +The D-bit shall always be set to 0. + +The Network Layer entity shall either ignore the D-bit in a received data packet, or treat as an error the occurrence of the D-bit set to 1 in a received data packet. If the Network Layer entity chooses to treat it as an error, it shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “D-bit procedure not supported” (value = 166). + +#### **6.3.2.9 Q-bit** + +The Q-bit shall be set to the same value in all data packets of a complete data packet sequence to be transmitted. + +The user data of a received complete data packet sequence shall be passed to the higher layers, if the Q-bit setting is the same in all packets of the sequence. Otherwise the Network Layer entity shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “Inconsistent Q-bit settings” (value = 83). + +#### 6.3.2.10 Protocol identifier + +The protocol identification in the Network Layer is described in the Technical Report ISO/IEC TR 9577 [15]. In ISO/IEC 8208 [13], the first octet of the call user data field within a CALL REQUEST/INCOMING CALL packet contains the “subsequent protocol identifier” (SPI) used to identify the higher layer protocols. + +For the application of Videotex the bit pattern of the SPI is: + +| bit | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +|-----|---|---|---|---|---|---|---|---| +| | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | + +This bit pattern corresponds to “CCITT X.29” in Table 4/ISO/IEC TR 9577 [15]. + +In outgoing calls, the call user data field of the CALL REQUEST packet shall contain the above bit pattern as first octet. + +In incoming calls, the above bit pattern shall be interpreted by the Network Layer entity that the Videotex application is requested. + +The contents of remaining octets (besides the first octet) of the call user data field within an INCOMING CALL packet shall be ignored by the Network Layer entity. + +#### 6.3.2.11 Address fields + +The CALL REQUEST packet shall contain the called DTE address. The encoding depends on the requirements of the PSPDN (see also 6.1.2). The use of the calling DTE address field is dependent on the requirements of the PSPDN. + +#### 6.3.2.12 Data Link Disconnection Request + +In the normal procedure for clearing, all calls should be cleared before requesting the disconnection of the Data Link. + +#### 6.3.2.13 Optional user facilities that shall be supported + +The packet level optional user facilities that shall be supported by the terminal are shown in Table 5. + +NOTE – For switched B-channel access, PSPDNs/ISDNs might offer only a restricted set of facilities (default profile). Thus, if a DTE (Videotex terminal) requests a specific facility, this might not be available or even cause the call to be cleared (e.g., flow control parameter negotiation is not allowed by the network). + +TABLE 5/T.103 + +#### Supported packet level optional user facilities + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|---------------------------------------|-----------------------------------| +| Default Throughput Classes Assignment | 13.11 | +| Flow Control Parameter Negotiation | 13.12 | +| Throughput Class Negotiation | 13.13 | + +### 6.3.2.14 Recommended optional user facilities and CCITT specified DTE facilities + +The packet level optional user facilities and CCITT specified DTE facilities that are shown in Table 6 are those for which implementation is recommended for greater flexibility. The use of the optional user facilities depends on operational requirements of the PSPDN. + +TABLE 6/T.103 + +#### Recommended facilities + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------| +| On-line Facility Registration | 13.1 | +| Fast Select Acceptance | 13.17 (Note) | +| Network User Identification (NUI) related facilities | 13.21 | +| Calling Address Extension | 14.1 | +| Called Address Extension | 14.2 | +| NOTE – Recommendation T.105 [5] allows the use and non-use of the Fast Select facility in an outgoing call. If the Past Select Acceptance facility is not required from a Videotex terminal, then the interworking between terminals that use and terminals that do not use the FS facility is not generally possible. | | + +### 6.3.2.15 Excluded Optional user facilities + +The packet level optional user facilities shown in Table 7 shall not be used. + +TABLE 7/T.103 + +#### Excluded facilities + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|------------------------------------------------|-----------------------------------| +| Extended Packet Sequence Numbering | 13.2 | +| Packet Retransmission | 13.4 | +| Non-standard Default Packet sizes | 13.9 | +| Non-standard Default Window sizes | 13.10 | +| Bilateral Closed User Group related facilities | 13.15 | +| ROA Selection related facilities | 13.23 | + +## **7 Access to the ISDN virtual circuit service (X.31 Case B) through the B-channel** + +### **7.1 Coordination between B-channel and D-channel** + +#### **7.1.1 General** + +ISDN videotex end-systems supporting access to ISDN virtual circuit services over the B-channel (X.31 [9] Case B) shall use a protocol stack at the S- or T- reference point in accordance with the standards as indicated in Figure 4 (see 4.3.2). + +One stack is used to support signalling on the D-channel for circuit switched access to the packet handling function (PH) of the ISDN. In the case of the semi-permanent B-channel service, this stack is null. The other stack is used to support packet switched signalling and information transfer. The detailed protocols are given in 7.2.2 and 7.3.2. + +Clause 11/CCITT Rec. T.105 [5] provides the definition of a Bearer Independent Service for syntax-based Videotex (SBV BIS) and the mapping of its elements to the protocol and procedures of ISO/IEC 8208 [13]. Additional requirements for calls originated by or directed toward the ISDN end-system are specified below. Co-ordination is only required for switched B-Channel ISDN connections between the end-system and the PH. + +#### **7.1.2 Outgoing calls** + +Additional procedures are required if a B-channel is not already established or if an additional B-channel is needed to support the additional traffic. + +The reception by layer 3 of a BIS-N-CONNECT request primitive shall first cause the ISDN D-Channel signalling procedure for demand access to be used to establish a B-Channel as indicated in 7.3. + +NOTE 1 – The “Called party number” information element of the SETUP message as defined in Recommendation Q.931 [7] is not used. + +After a successful establishment of this B-channel connection, the procedures of clause 11/T.105 [5] shall apply. + +NOTE 2 – The called address in the X.25 CALL REQUEST packet (derived from the BIS-N-CONNECT request primitive) is used for routing through the Access Network to the Access Function. + +Failure to establish the channel connection is indicated to the BIS user by means of a BIS-N-DISCONNECT indication primitive with the originator parameter indicating “ISDN” and the reason parameter filled as indicated in 7.1.5. + +#### **7.1.3 Incoming calls** + +Additional procedures are required if an ISDN end-system interface has subscribed to the “Conditional notification” class, and the network uses the call offering procedures as described in 7.3.1.4 and 6.2.2.3.1/X.31 [9]. + +The ISDN call offering procedures determine which B-channel is to be used. If the network does not indicate an exclusive channel, the ISDN end-system may select (see Note) an already established B-channel. These procedures are not visible to the BIS user. + +#### **NOTES** + +1 Either the “point-to-point” configuration or the “point-to-multipoint” configuration support this B-channel negotiation. + +2 It is not recommended that the terminal chooses an already established B-channel if the network indicates “preferred B-channel” (see Table 6-3/X.31, subclause 6.2.2.3.2 (SETUP message)). + +3 A negotiation between idle B-channel and established B-channel presents technical difficulties from the network point of view. Nevertheless, in case of the “No notification” class, the network will have to use an already established B-channel to send an INCOMING CALL packet to the user (6.2.2/X.31 [9]). This seems to present similar technical difficulties for the network. + +After the successful establishment of this B-channel connection, or successful selection of an already established B-channel, the procedures specified in 7.2.2 and 7.3.2 and in clause 11/T.105 [5] shall apply. + +#### **7.1.4 Clearing virtual circuits** + +It is recommended that the NL entity starts a timer T320 (see Recommendation Q.931 [7]) after the last SBV Network Connection has been released. This timer is cleared upon establishment of the next virtual circuit. Upon expiry of T320, clearing of the B-channel should be initiated. + +These procedures are not visible to the BIS user. + +#### **7.1.5 Error handling** + +If one or more SBV Network Connections are established or in the process of being established on an established B-channel and that B-channel is disconnected, this disconnection shall be indicated to the BIS user by means of a BIS-N-DISCONNECT indication primitive with the originator parameter indicating "ISDN". + +The reason parameter is as given in subclause 6.1.5 for each of the SBV Network Connections established or in the process of being established. + +### **7.2 Layer 2 protocols** + +#### **7.2.1 Layer 2 protocol for the D-channel** + +The base Recommendation for the layer 2 protocol of the D-channel is Recommendation Q.921 [6]. The provisions of Recommendation Q.921 [6] applicable to Data Link Connections between SAPs used for call control procedures (SAPI = 0) are valid without further application rules. + +NOTE – The D-channel protocol is only applicable to switched ISDN connections between the terminal and the PH. + +#### **7.2.2 Layer 2 protocol for the B-channel** + +The base Recommendation for the layer 2 protocol in the B-channel is ISO 7776 [12]. The conformance requirements for the Data Link Layer in the B-channel shall be in accordance with the base Recommendation with respect to DTE/DCE operation, and subject to the additional requirements as detailed in the remainder of this subclause. + +NOTE – CCITT X.25 [8] LAPB may also be taken as base Recommendation, however explicit references to subclauses are only made with respect to ISO 7776 [12] in this Recommendation. + +##### **7.2.2.1 Application rules** + +The application rules of Table 8 shall apply. + +##### **7.2.2.2 Implementation recommendations** + +The implementation recommendations for layer 2 of the B-channel are contained in Table 9. + +### **7.3 Layer 3 protocols** + +#### **7.3.1 Layer 3 protocol for the D-channel** + +##### **7.3.1.1 The access protocol** + +The base Recommendation for the layer 3 protocol of the D-channel is Recommendation Q.931 [7]. The requirements of the base standards shall apply, subject to the provisions of Recommendation X.31 [9] (as far as applicable to terminals accessing the ISDN virtual circuit service over the B-channel), and subject to the provisions of the subsequent subclauses. + +##### **NOTES** + +- 1 The D-channel protocol is only applicable to switched ISDN connections between the terminal and the PH. +- 2 Annex F (normative) defines the messages for the control of packet-mode access connections. + +##### **7.3.1.2 Terminal addresses** + +Subclause 4.1/X.31 [9] shall apply. For the use of addressing supplementary services, refer to 7.3.1.6. + +TABLE 8/T.103 + +**Application rules for B-Channel layer 2** + +| Case | Item | Application Rule | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| a | Single link procedure | Only the single link procedure shall be supported. | +| b | Independence of LAPB protocols | An independent LAPB protocol shall operate over each B-channel. | +| c | Data Link set-up | The responsibility for Data Link set-up depends on the notification class and on other agreements with the network provider. Table B.1 (informative) shows the different possibilities. | +| d | Maximum frame length N1 | Parameter N1 (maximum number of bits in an I-frame) shall be such that the Data Link layer is capable of carrying the maximum packet size negotiated at the packet level, plus the related packet level and Data Link level control information. Guidance on the derivation of the value of N1 can be found in Appendix II/X.25 [8]. | +| e | Link set-up in FRMR condition | The DTE shall support the procedure of transmitting an FRMR response frame up to N2 times, if necessary. In order to get the DCE to reset the link. | +| f | Address assignment | The address assignment shall be as defined in 5.1/ISO 7776 [12]. | +| g | Modes of operation | Basic (module 8) operation shall be supported. | +| h | Window size k | For parameter k (window size), the support of the value 7 is mandatory for basic operation. | +| i | Disconnection order | In the normal procedure for disconnection, the Data Link shall be disconnected before disconnecting the B-channel. | +| NOTE – The different draft functional standards specify the use of basic mode only. However, extended mode is not ruled out explicitly and is for further study. | | | + +TABLE 9/T.103 + +**Implementation recommendations for B-channel layer 2** + +| Case | Item | Implementation recommendations | +|------|-------------------------|---------------------------------------------------------------------------------------------------------------------------------| +| a | Parameter N2 | For parameter N2 (maximum number of attempts) the value 10 is recommended. | +| b | Timer T1 | It is recommended that the value of Timer T1 (retransmission) is tuneable in the range from 100 ms to 15 s. | +| c | I-frame acknowledgement | It is recommended that an RR frame be used as an acknowledgement of received I-frames, unless an outgoing I-frame is available. | +| d | Timer T3 | If implemented, Timer T3 (disconnected) is recommended to be greater than or equal to $T1 \times 10$ . | +| e | Timer T4 | It is recommended to implement Timer T4. | + +**7.3.1.3 Outgoing calls** + +The requirements of subclauses 4.3.2 and 6.1.2.1/X.31 [9] apply without modification. + +NOTE – No called party number and no called party sub-address is contained in the SETUP message. Some networks may require the inclusion of the calling party number and/or calling party sub-address in the SETUP message. + +The Bearer Capability information element shall be coded as indicated in Table 10. Fields not shown in the table shall be omitted. + +Low Layer Compatibility and High Layer Compatibility information elements shall not be included in the SETUP message. + +TABLE 10/T.103 + +**Coding of the Bearer Capability information element** + +| Octets | Information element field | Field value | +|--------|-------------------------------------------|----------------------------------| +| 1 | Information element identifier | Bearer capability | +| 2 | Length of contents of information element | 00000100 | +| 3 | Coding standard | CCITT standardized coding | +| | Information transfer capability | Unrestricted digital information | +| 4 | Transfer mode | Packet mode | +| | Information transfer rate | 00000: packet | +| 6 | User information layer 2 protocol | X.25 link layer | +| 7 | User information layer 3 protocol | X.25 packet layer | + +#### 7.3.1.4 Incoming calls + +To select a called terminal correctly, the terminal(s) at the user/network interface will be served with information generated by the calling terminal and the intermediate network(s). + +The terminal selection functions and procedures are specified in Recommendation I.333 [2]. + +Annex B/Q.931 [7] specifies the procedure of compatibility checking as part of the access protocol. The information elements to be considered are those containing address information and the Bearer Capability information element. + +The requirements of Annex B/Q.931 [7] shall apply. The following rules specify further details on terminal selection and compatibility checking and add requirements for Syntax-based Videotex terminals. + +The result of this procedure is to decide, whether to ignore, to reject or to accept the incoming call. + +a) *B.3.1/Q.931 [7]* + +If a call is offered with address information, this information shall be checked against the local address before network-to-user compatibility checking. In this context, Note 1 of B.3.1/Q.931 [7] is not applicable. + +In case of mismatch of any presented address information, no further compatibility checking is required and the call shall be ignored. + +If no address information is offered, or the offered address information is not complete with respect to the local address (e.g. because the Sub-addressing supplementary service is subscribed, but the called subaddress is not offered), the terminal shall continue with network-to-user compatibility checking. It is not allowed to ignore a call for missing address information only. + +b) *B.3.2/Q.931 [7]* + +A terminal matches the received network-to-user information, if the information in the received Bearer Capability information element offered in the SETUP message is exactly as specified in Table 10 (i.e. fields not indicated in this table shall not be present). + +If a mismatch is detected while checking the Bearer Capability information element, the terminal shall reject the call in accordance to 5.2.5.1/Q.931 [7]. It is not permitted to ignore the call. + +c) *B.3.3/Q.931 [7]* + +Received Low Layer Compatibility and High Layer Compatibility information elements shall be ignored. + +d) *B.3.4/Q.931 [7]* + +This subclause requires user actions to be carried out as result of compatibility checking. It is superseded by this Recommendation. + +If a terminal has not rejected or ignored the call while following the procedures a), b), c) and d), it shall accept the call or reject it for other reasons (see below). + +If a terminal is obliged to reject the call while following the procedures a) to d), the cause code to be used is defined in B.3/Q.931 [7]. + +If a terminal rejects the call for different reasons, it should indicate a cause from the following list: + +- a) cause code #17: User busy (already involved in another call); +- b) cause code #47: Resources unavailable, unspecified; +- c) cause code #21: Call rejected (e.g. other local reasons apply). + +If the terminal accepts the Incoming call, the co-ordination function initiates the appropriate Link Layer and Network Layer functions in the B-channel as detailed in 7. 1. + +### **7.3.1.5 Release of the switched connection** + +Subclause 6.4.1/X31 [9] applies. However the terminal shall not release the switched connection while a virtual call is established or in the process of being established over the related B-channel. + +NOTE – Further requirements on handling of failures or premature clearing of the switched connection can be found in the description of the co-ordination function in 7. 1. + +### **7.3.1.6 Supplementary services** + +The use of supplementary services of a specific ISDN depends on provisions and requirements of the network. + +The procedures for UUS are specified in Recommendation Q.931 [7]. + +The addressing supplementary services: DDI (Direct-Dialling-In), MSN (Multiple Subscriber Number) or SUB (Sub-addressing), or a combination of them, may be useful or even required by the network, if multiple terminals have been attached to the same ISDN address. + +The TP (Terminal Portability) supplementary service shall not be used. + +### **7.3.2 Layer 3 protocol for the B-channel** + +The base recommendation for the Network Layer in the B-channel is ISO/IEC 8208 [13]. The conformance requirements for the Network Layer in the B-channel shall be in accordance with the base recommendation with respect to DTE/DCE operation, and subject to the additional requirements as detailed in the remainder of this subclause, + +NOTE – CCITT X.25 [8] PLP may also be taken as base recommendation, however explicit references to subclauses are only made with respect to ISO/IEC 8208 [13] in this Recommendation. + +#### **7.3.2.1 Bearer Independent Service** + +The service that the Network Layer entity provides to the Videotex application with respect to set-up, clear, reset of Network Connections and data transfer over established Network Connections, shall be as described in clause 11/T.105 [5]. + +### **7.3.2.2 Operation over multiple B-channels** + +If a terminal operates more than one B-channel, the Network Layer of each B-channel connection shall be processed independently from the Network Layer of each other B-channel connection. + +### **7.3.2.3 DTE role** + +The Network Layer entity shall adopt the role of a DTE. + +### **7.3.2.4 Logical channels to be used** + +The logical channel ranges (UC, HIC, LTC, HTC, LOC and HOC) to be used are determined by local knowledge. If local knowledge is not available, then by default only a single two-way logical channel shall be used (i.e. LTC and HTC will be set to 1, while LIC, HIC, LOC and HOC shall be set to zero). If more than one logical channel is available, a higher value of HTC may be negotiated using the On line Facility Registration facility. + +If a DTE is capable of initiating a REGISTRATION request packet, then the registration parameters shall be set as follows: + +- The LIC, HIC, LOC and HOC parameter shall be set to zero. The LTC shall be set to the value of 1. The value in the “total number of logical channels” parameter field shall be set equal to the value in the HTC parameter field. + +### **7.3.2.5 Packet sizes** + +The Network Layer entity shall be capable of supporting the standard default packet size of 128 octets. The only permitted maximum data packet sizes are 128, 256, 512, 1024 and 2048 octets. Packet sizes other than the standard default packet size may be negotiated on a per call basis using the “Flow Control Parameter Negotiation” facility. + +### **7.3.2.6 Default packet level window size** + +The Network Layer entity shall be capable of supporting the standard default window size of 2. Other window sizes may be negotiated on a per call basis using the “Flow Control Parameter Negotiation” facility. + +### **7.3.2.7 Default throughput class** + +The default throughput class assigned to each direction of transmission shall be 64 kbit/s. Other default throughput class values may be agreed on a subscription basis. Other throughput classes may be negotiated on a per call basis using the “Throughput Class Negotiation” facility. + +### **7.3.2.8 D-bit** + +The D-bit shall always be set to 0. + +The Network Layer entity shall either ignore the D-bit in a received data packet, or treat as an error the occurrence of the D-bit set to 1 in a received data packet. If the Network Layer entity chooses to treat it as an error, it shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “D-bit procedure not supported” (value = 166). + +### **7.3.2.9 Q-bit** + +The Q-bit shall be set to the same value in all data packets of a complete data packet sequence to be transmitted. + +The user data of a received complete data packet sequence shall be passed to the higher layers, if the Q-bit setting is the same in all packets of the sequence. Otherwise the Network Layer entity shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “Inconsistent Q-bit settings” (value = 83). + +### **7.3.2.10 Protocol identifier** + +The protocol identification in the Network Layer is described in the Technical Report ISO/IEC TA 9577 [15]. In ISO/IEC 8208 [13], the first octet of the call user data field within a CALL REQUEST/INCOMING CALL packet contains the “subsequent protocol identifier” (SPI) used to identify the higher layer protocols. + +For the application of Videotex the bit pattern of the SPI is: + +| | | | | | | | | | +|-----|---|---|---|---|---|---|---|---| +| bit | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | + +This bit pattern corresponds to “CCITT X.29” in Table 4/ISO/IEC TR 9577 [15]. + +In outgoing calls, the call user data field of the CALL REQUEST packet shall contain the above bit pattern as first octet. + +In incoming calls, the above bit pattern shall be interpreted by the Network Layer entity that the Videotex application is requested. + +The contents of remaining octets (besides the first octet) of the call user data field within an INCOMING CALL packet shall be ignored by the Network Layer entity. + +### 7.3.2.11 Address fields + +The CALL REQUEST packet shall contain the called DTE address. The encoding depends on the requirements of the PSPDN/ISDN. The use of the calling DTE address field is dependent on the requirements of the PSPDN/ISDN. + +### 7.3.2.12 Data Link Disconnection Request + +In the normal Procedure for clearing, all calls should be cleared before requesting the disconnection of the Data Link + +### 7.3.2.13 Optional user facilities that shall be supported + +The packet level optional user facilities that shall be supported by the terminal are shown in Table 11. + +NOTE – For switched B-channel access. PSPDNs/ISDNs might offer only a restricted set of facilities (default profile). Thus, if a DTE (Videotex terminal) requests a specific facility, this might not be available or even cause the call to be cleared (e.g. flow control parameter negotiation is not allowed by the network). + +TABLE 11/T.103 + +#### Supported packet level optional user facilities + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|---------------------------------------|-----------------------------------| +| Default Throughput Classes Assignment | 13.11 | +| Flow Control Parameter Negotiation | 13.12 | +| Throughput Class Negotiation | 13.13 | + +### 7.3.2.14 Recommended optional user facilities and CCITT specified DTE facilities + +The packet level optional user facilities and CCITT specified DTE facilities that are shown in Table 12 are those for which implementation is recommended for greater flexibility. The use of the optional user facilities depends on operational requirements of the PSPDN/ISDN. + +TABLE 12/T.103 + +**Recommended facilities** + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------| +| On-line Facility Registration | 13.1 | +| Fast Select Acceptance | 13.17 (Note) | +| Network User Identification (NUI) related facilities | 13.21 | +| Calling Address Extension | 14.1 | +| Called Address Extension | 14.2 | +| NOTE – Recommendation T.105 [5] allows the use and non-use of the Fast Select facility in an outgoing call. If the Fast Select Acceptance facility is not required from a Videotex terminal, then the interworking between terminals that use and terminals that do not use the FS facility is not generally possible. | | + +**7.3.2.15 Excluded optional user facilities** + +The packet level optional user facilities shown in Table 13 shall not be used. + +TABLE 13/T.103 + +**Excluded facilities** + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|------------------------------------------------|-----------------------------------| +| Extended Packet Sequence Numbering | 13.2 | +| Packet Retransmission | 13.4 | +| Bilateral Closed User Group related facilities | 13.15 | +| Charging Information | 13.22 | +| ROA Selection related facilities | 13.23 | + +**8 Access to the ISDN virtual circuit service (X.31 Case B) through the D-channel****8.1 Layer 2 protocol****8.1.1 The base Recommendation** + +The base Recommendation for the layer 2 protocol in the D-channel is Recommendation Q.921 [6]. + +If call offering procedures including channel selection are implemented (see clause 4), the provisions of Recommendation Q.921 [6] applicable to Data Link Connections between SAPs used for call control procedures (SAPI=0) shall apply, with additional requirements indicated in the subsequent subclauses. + +NOTE – Call offering over ISDN layer 2 procedures using SAPI = 16 are not supported. + +A single Data Link Connection with SAPI = 16 shall be used to carry the packets of the Network Layer in numbered I-frames. The provisions of Recommendation Q.921 [6] shall apply with additional requirements as indicated in the subsequent subclauses. + +### **8.1.2 Same Connection Endpoint Suffix (CES)** + +If call offering procedures are used, the CES shall be the same in the signalling phase and in the data transfer phase for a given communication. + +### **8.1.3 Responsibility for Data Link set-up** + +The responsibility for Data Link set-up depends on the notification class and is agreed with the network. Table B.3 shows the different possibilities. + +## **8.2 Layer 3 protocols** + +### **8.2.1 General** + +Two different protocols are applicable to Network Layer operations over the D-channel: + +- 1) The protocol used to notify the NL entity of an incoming call +Additional procedures are required, if the ISDN end-system has subscribed to the “Conditional notification” class, and the network uses the call offering procedures as described in 8.2.2.4 and 8.2.2.5. These procedures are not visible to the BIS user. +- 2) The protocol used for packet data communications over the D-channel as described in 8.2.3. + +### **8.2.2 Layer 3 ISDN signalling protocols** + +#### **8.2.2.1 The base Recommendation** + +The base Recommendation for the layer 3 protocol of the D-channel used for notification of an incoming call is Recommendation Q.931 [7]. The requirements of the base standards shall apply, subject to the provisions of Recommendation X.31 [9] (as far as applicable to terminals accessing the ISDN virtual circuit service over the D-channel). and subject to the provisions of the subsequent subclauses. + +NOTE – Annex F (normative) defines the messages for the control of packet-mode access connections and the coding of their information elements. + +#### **8.2.2.2 Terminal addresses** + +Subclause 4.1/X.31 [9] shall apply. For the use of addressing supplementary services see 8.2.2.6 below. + +#### **8.2.2.3 Outgoing calls** + +The protocol is not applicable for outgoing calls on the D-channel. + +#### **8.2.2.4 Incoming calls** + +To select a called terminal correctly, the terminal(s) at the user/network interface will be served with information generated by the calling terminal and the intermediate network(s). + +The terminal selection functions and procedures are specified in Recommendation I.333 [2]. Compatibility checking for terminals supporting specific basic services is described in ETR 018 [(?)]. + +Annex B/Q.931 [7] specifies the procedure of compatibility checking as part of the access protocol. The information elements to be considered are those containing address information and the Bearer Capability information element. + +The requirements of Annex B/Q.931 [7] shall apply. The following rules specify further details on terminal selection and compatibility checking and add requirements for Syntax-based Videotex terminals. + +The result of this procedure is to decide, whether to ignore, to reject or to accept the incoming call. + +##### **a) B.3.1/Q.931 [7]** + +If a call is offered with address information, this information shall be checked against the local address before network-to-user compatibility checking. In this context, Note 1 of B.3.1/Q.931 [7] is not applicable. + +In case of mismatch of any presented address information, no further compatibility checking is required and the call shall be ignored. + +If no address information is offered, or the offered address information is not complete with respect to the local address (e.g. because the Sub-addressing supplementary service is subscribed, but the called subaddress is not offered), the terminal shall continue with network-to user compatibility checking. It is not allowed to ignore a call for missing address information only. + +b) *B.3.2/Q.931 [7]* + +A terminal matches the received network-to-user information, if the information in the received Bearer Capability information element offered in the SETUP message is exactly as specified in Table 14 (i.e. fields not indicated in this Table shall not be present). + +If a mismatch is detected while checking the Bearer Capability information element, the terminal shall reject the call in accordance to 5.2.5.1/Q.931 [7]. It is not permitted to ignore the call. + +c) *B.3.3/Q.931 [7]* + +Received Low Layer Compatibility and High Layer Compatibility information elements shall be ignored. + +d) *B.3.4/Q.931 [7]* + +This subclause requires user actions to be carried out as result of compatibility checking. It is superseded by this Recommendation. + +TABLE 14/T.103 + +**Coding of the Bearer Capability information element** + +| Octets | Information element field | Field value | +|--------|-------------------------------------------|----------------------------------| +| 1 | Information element identifier | Bearer capability | +| 2 | Length of contents of information element | 00000100 | +| 3 | Coding standard | CCITT standardized coding | +| | Information transfer capability | Unrestricted digital information | +| 4 | Transfer mode | Packet mode | +| | Information transfer rate | 00000: packet | +| 6 | User information layer 2 protocol | Recommendation Q.921/I.441 | +| 7 | User information layer 3 protocol | Recommendation X.25 packet level | + +If a terminal has not rejected or ignored the call while following the procedures a), b), c) and d), it shall accept the call or reject it for other reasons (see below). + +If a terminal is obliged to reject the call while following the procedures a) to d), the cause code to be used is defined in B.3/Q.931 [7]. + +If a terminal rejects the call for different reasons, it should indicate a cause from the following list: + +- a) cause code #17: User busy (already involved in another call); +- b) cause code #47: Resources unavailable, unspecified; +- c) cause code #21: Call rejected (e.g. other local reasons apply). + +If the terminal accepts the incoming call, the terminal initiates the appropriate Link Layer and Network Layer functions in the D-channel as detailed in 8.1 and 8.2.3. + +### **8.2.2.5 Release of the call** + +Subclause 6.2.2.3.1/X.31 [9] applies with respect to selection of the D-channel. + +NOTE – After having received the CONNECT message from the accepting terminal, the network will release the call with a RELEASE message containing cause code #7 “call awarded and being delivered in an established channel”. + +### **8.2.2.6 Supplementary services** + +The use of supplementary services of a specific ISDN depends on provisions and requirements of the network. + +The procedures for UUS are specified in Recommendation Q.931 [7]. + +The addressing supplementary services: DDI (Direct-Dialling-In), MSN (Multiple Subscriber Number) or SUB (Sub-addressing), or a combination of them, may be useful or even required by the network, if multiple terminals have been attached to the same ISDN address. + +The TP (Terminal Portability) supplementary service shall not be used. + +## **8.2.3 Layer 3 data communication protocol** + +The base Recommendation for the Network Layer in the D-channel is ISO/IEC 8208 [13]. The conformance requirements for the Network Layer in the D-channel shall be in accordance with the base Recommendation with respect to DTE/DCE operation, and subject to the additional requirements as detailed in the remainder of this subclause. + +NOTE – CCITT X.25 [8] PLP may also be taken as base Recommendation, however explicit references to subclauses are made in this Recommendation only with respect to ISO/IEC 8208 [13]. + +### **8.2.3.1 Bearer Independent Service** + +The service that the Network Layer entity provides to the Videotex application with respect to set-up, clear, reset of Network Connections and data transfer over established Network Connections, shall be as described in clause 11/T.105 [5]. + +### **8.2.3.2 Operation over p-Data Link Connections** + +The Network Layer entity shall operate over a single p-Data Link Connection (SAPI = 16). + +If a terminal supports more than one TEI, the Network Layer entity of each p-Data Link Connection shall be processed independently from the Network Layer entities of the other p-Data Link Connections. + +### **8.2.3.3 DTE role** + +The Network Layer entity shall adopt the role of a DTE. + +### **8.2.3.4 Logical channels to be used** + +The logical channel ranges (LIC, HIC, LTC, HTC, LOC and HOC) to be used are determined by local knowledge. If local knowledge is not available, then by default only a single two-way logical channel shall be used. (i.e. LTC and HTC will be set to 1, while LIC, HIC, LOC and HOC shall be set to zero). If more than one logical channel is available, a higher value of HTC may be negotiated using the On-line Facility Registration facility. + +If a DTE is capable of initiating a REGISTRATION request packet, then the registration parameters shall be set as follows: + +- The LIC, HIC, LOC and HOC parameter shall be set to zero. The LTC shall be set to the value of 1. The value in the “total number of logical channels” parameter field shall be set equal to the value in the HTC parameter field. + +### **8.2.3.5 Packet sizes** + +The Network Layer entity shall be capable of supporting the standard default packet size of 128 octets. The only permitted maximum data packet sizes are 128 and 256 octets. Packet sizes other than the standard default packet size may be negotiated on a per call basis using the “Flow Control Parameter Negotiation” facility. + +### **8.2.3.6 Default packet level window size** + +The Network Layer entity shall be capable of supporting the standard default window size of 2. Other window sizes may be negotiated on a per call basis using the “Flow Control Parameter Negotiation” facility. + +### 8.2.3.7 Default throughput class + +The default throughput class assigned to each direction of transmission shall be 9.6 kbit/s. Other default throughput class values may be agreed on a subscription basis. + +Other throughput classes may be negotiated on a per call basis using the “Throughput Class Negotiation” facility. The maximum negotiable throughput class shall be 9.6 kbit/s at the Basic Rate Inter-face, and 64 kbit/s at the Primary Rate Interface. + +### 8.2.3.8 D-bit + +The D-bit shall always be set to 0. + +The Network Layer entity shall either ignore the D-bit in a received data packet, or treat as an error the occurrence of the D-bit set to 1 in a received data packet. If the Network Layer entity chooses to treat it as an error, it shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “D-bit procedure not supported” (value = 166). + +### 8.2.3.9 Q-bit + +The Q-bit shall be set to the same value in all data packets of a complete data packet sequence to be transmitted. + +The user data of a received complete data packet sequence shall be passed to the higher layers, if the Q-bit setting is the same in all packets of the sequence. Otherwise the Network Layer entity shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “Inconsistent Q-bit settings” (value = 83). + +### 8.2.3.10 Protocol identifier + +The protocol identification in the Network Layer is described in the Technical Report ISO/IEC TR 9577 [15]. In ISO/IEC 8208 [13], the first octet of the call user data field within a CALL REQUEST/INCOMING CALL packet contains the “subsequent protocol identifier” (SPI) used to identify the higher layer protocols. + +For the application of Videotex the bit pattern of the SPI is: + +| | | | | | | | | | +|-----|---|---|---|---|---|---|---|---| +| bit | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | +| | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | + +This bit pattern corresponds to “CCITT X.29” in Table 4/ISO/IEC TR 9577 [15]. + +In outgoing calls, the call user data field of the CALL REQUEST packet shall contain the above bit pattern as first octet. + +In incoming calls, the above bit pattern shall be interpreted by the Network Layer entity that the Videotex application is requested. + +The contents of remaining octets (besides the first octet) of the call user data field within an INCOMING CALL packet shall be ignored by the Network Layer entity. + +### 8.2.3.11 Address fields + +The CALL REQUEST packet shall contain the called DTE address. The encoding depends on the requirements of the PSPDN/ISDN. The use of the calling DTE address field is dependent on the requirements of the PSPDN/ISDN. + +### 8.2.3.12 Data Link Disconnection Request + +In the normal procedure for clearing, all calls should be cleared before requesting the disconnection of the Data Link. + +### 8.2.3.13 Optional user facilities that shall be supported + +The packet level optional user facilities that shall be supported by the terminal are shown in Table 15. + +NOTE – For switched B-channel access, PSPDNs/ISDNs might offer only a restricted set of facilities (default profile). Thus, if a DTE (Videotex terminal) requests a specific facility, this might not be available or even cause the call to be cleared (e.g. flow control parameter negotiation is not allowed by the network). + +TABLE 15/T.103 + +**Supported packet level optional user facilities** + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|---------------------------------------|-----------------------------------| +| Default Throughput Classes Assignment | 13.11 | +| Flow Control Parameter Negotiation | 13.12 | +| Throughput Class Negotiation | 13.13 | + +**8.2.3.14 Recommended optional user facilities and CCITT specified DTE facilities** + +The packet level optional user facilities and CCITT specified DTE facilities that are shown in Table 16 are those for which implementation is recommended for greater flexibility. The use of the optional user facilities depends on operational requirements of the PSPDN/ISDN. + +TABLE 16/T.103 + +**Recommended facilities** + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------| +| On-line Facility Registration | 13.1 | +| Fast Select Acceptance | 13.17 (Note) | +| Network User Identification (NUI) related facilities | 13.21 | +| Calling Address Extension | 14.1 | +| Called Address Extension | 14.2 | +|

NOTES

1 Recommendation T.105 [5 ] allows the use and non-use of the Fast Select facility in an outgoing call. If the Fast Select Acceptance facility is not required from a Videotex terminal, then the interworking between terminals that use and terminals that do not use the FS facility is not generally possible.

2 The recommended facilities are equal to those taken for Case B/B-channel. T/ 1221 recommends no facilities at all. The difference should be discussed.

| | + +**8.2.3.15 Excluded optional user facilities** + +The packet level optional user facilities shown in Table 17 shall not be used. + +TABLE 17/T.103 + +**Excluded facilities** + +| Facility | ISO/IEC 8208 [13]
(Subclauses) | +|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------| +| Extended Packet Sequence Numbering | 13.2 | +| Packet Retransmission | 13.4 | +| Bilateral Closed User Group related facilities | 13.15 | +| Charging Information | 13.22 | +| ROA Selection related facilities | 13.23 | +| NOTE – The excluded facilities are equal to those taken for Case B/B-channel. T/1221 excludes only extended packet sequence numbering. The difference should be discussed. | | + +## **Annex A** + +(informative) + +### **ISDN lower layer communication modes for syntax-based Videotex** + +(This annex does not form an integral part of this Recommendation) + +The X.25-based ISDN end-system may have one or several possibilities to establish a communication with another end-system. DTE/DTE mode of communication, X.31 Case A access, X.31 Case B/B-channel access, or X.31 Case B/D-channel access. + +For Videotex end-systems, establishment and release of channel connections and data transfer on these connections is provided by the SBV Bearer Independent Service (SBV BIS) defined in Recommendation T.105 [5] through the use of Virtual Circuit services of the X.25 [8] Packet Layer Protocol (X.25/PLP). + +Moreover, the ISDN interface may require some coordination between the signalling ISDN protocol (the out-of-band protocol) and the X.25 [8] protocol (the in-band protocol). The procedures for this coordination depend on the communication case selected. + +Figure A.1 presents the structure of the lower layers for the four cases considered above: + +Upon the reception of a BIS-N-CONNECT request primitive from the higher layers, or in the case of incoming calls, the Network Layer entity may have to choose among the possibilities for case selection implemented in the ISDN end-system, or may at least have to check the compatibility between the request and these possibilities. + +In the case of simultaneous multiple network connections, different modes of communication may be used for each of them, e.g. the D-channel for alphamosaic data and a B-channel for photographic data. + +Annex B (informative) describes the parameters which may influence the access to X.25 [8] packet services and the selection of a particular mode of communication. + +![Diagram of ISDN lower layers for ISDN syntax-based videotex. The diagram shows a three-layer architecture (Layer 1, Layer 2, Layer 3) for a 'Syntax-based videotex network service'. Layer 3 includes 'Case selection' and 'Coordination' blocks with 'BIS' sub-blocks. Layer 2 includes 'LAPD' and 'LAPB' blocks. Layer 1 includes 'BRA/PRA' blocks. The diagram is divided into 'Circuit mode bearer service' (Rec. T.102) and 'Packet mode bearer service' (This Recommendation). Cases shown are 'DTE/DTE', 'Case A', 'Case B/B-ch', and 'Case B/D-ch'.](9a5927586a691c4908aa2cf98bd47ebb_img.jpg) + +The diagram illustrates the ISDN lower layers for a syntax-based videotex network service, organized into three layers: + +- Layer 3:** Contains a 'Case selection' block at the top. Below it, there are four main sections: 'DTE/DTE', 'Case A', 'Case B/B-ch', and 'Case B/D-ch'. Each section contains a 'Coordination' block with a 'BIS' (Bearer Independent Service) sub-block. The 'DTE/DTE' section is further divided into 'D' and 'B' channels. +- Layer 2:** Contains 'LAPD' and 'LAPB' (Link Access Procedure in Balanced mode) blocks. The 'DTE/DTE' section has two blocks, while 'Case A', 'Case B/B-ch', and 'Case B/D-ch' each have one. +- Layer 1:** Contains 'BRA/PRA' (Basic Rate Access/Primary Rate Access) blocks. Each of the four cases has one such block. + +At the bottom, the diagram is divided into two service types: + +- Circuit mode bearer service:** Corresponds to 'Rec. T.102' and covers the 'DTE/DTE' and 'Case A' sections. +- Packet mode bearer service:** Corresponds to 'This Recommendation' and covers the 'Case B/B-ch' and 'Case B/D-ch' sections. + +Vertical dashed lines separate the four cases. Horizontal lines separate the layers. Arrows indicate the flow of data and control between components. + +Diagram of ISDN lower layers for ISDN syntax-based videotex. The diagram shows a three-layer architecture (Layer 1, Layer 2, Layer 3) for a 'Syntax-based videotex network service'. Layer 3 includes 'Case selection' and 'Coordination' blocks with 'BIS' sub-blocks. Layer 2 includes 'LAPD' and 'LAPB' blocks. Layer 1 includes 'BRA/PRA' blocks. The diagram is divided into 'Circuit mode bearer service' (Rec. T.102) and 'Packet mode bearer service' (This Recommendation). Cases shown are 'DTE/DTE', 'Case A', 'Case B/B-ch', and 'Case B/D-ch'. + +T0818430-94/d03 + +| | | +|--------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Coordination | Refer to the coordination function described in subclauses 6.1, 7.1 and clause 8 | +| BIS | Refer to the syntax-based videotex independent bearer service defined in Recommendation T.105 [5] | +| Call | Refer to the basic call control procedures defined in Recommendation Q.931 [7] | +| X.25 | Refer to the network layer protocol defined in ISO/IEC 8208 [13] | +| LAPD | Refer to the ISDN data link layer defined in Recommendation Q.921 [6] | +| LAPB | Refer to the HDLC procedures defined in ISO 7776 [12] | +| BRA/PRA | Refer to the physical network-user interfaces for either Basic Rate Access (BRA) or Primary Rate Interface (PRA) as defined in Recommendation I.430 [3] or Recommendation I.431 [4], respectively | + +FIGURE A.1/T.103 +ISDN lower layers for ISDN syntax-based videotex + +## **Annex B** + +(informative) + +### **Overview on communication establishment parameters** + +(This annex does not form an integral part of this Recommendation) + +#### **B.1 General** + +A terminal equipment (acting as a Videotex terminal or a Videotex access function) may have several possibilities to access the X.25 [8] packet service at the S/T reference point. These possibilities are determined by parameters which have to be fixed either at subscription time or dynamically when using the access. + +Subclause B.2 presents the parameters involved and their possible usage. + +Subclause B.3 presents the parameters involved in the case selection and highlight when a coordination is needed between the two protocol stacks of out-band signalling (Recommendation Q.931 [7] protocol) and in-band signalling (X.25 [8] protocol). + +#### **B.2 X.25 packet service access** + +##### **B.2.1 X.25 packet service access parameters** + +Recommendation X.31 [9] allows several possibilities to access the X.25 [8] packet services. The options applicable to this Recommendation are listed below. These options depend on several parameters indicated in Table B.1. The values of these parameters may be combined as detailed in Tables B.2 and B.3. Only virtual circuit services are within the scope of this Recommendation. + +TABLE B.1/T.103 + +**Parameters influencing the access of X.25 [8] packet services over an ISDN** + +| Parameter | Values | Comment | +|---------------------------------------------------|----------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| B-channel access type | Semi-permanent
Switched | B-channel connection is set up at subscription time and the physical layer is kept activated by the network in case of a basic rate interface.
Q.931 [7] procedures are used to set up and to disconnect a B-channel. | +| Notification class | No notification
Conditional notification | As defined in Recommendation X.31 [9]. | +| In band Layer 2 activation type (B- or D-channel) | Semi-permanent
User demand
Originator demand | Layer 2 is activated at subscription time and held activated by the network.
The user is responsible to set up the data link (the PH will clear an INCOMING CALL if the data link is not activated).
The responsibility for the data link set-up depends on the direction of the first virtual call. | +| TEI assignment | Fixed
Dynamic | TEI fixed at subscription time.
Dynamic TEI assignment using Recommendation Q.921 [6] procedures. | +| X-25 packet service type | Customized
Identified
Non-identified | As defined in Recommendation X.32 [10]. | + +### B.2.2 Access of X.25 packet services over the B-channel (X.31 Case A or Case B) + +Table B.2 shows the valid parameter combinations to access X.25 [8] packet services over the B-channel. + +TABLE B.2/T.103 + +#### Parameter combinations for B-channel services + +| Notification class | B-channel access type | Layer 2 activation | X.25 packet service types | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------|-------------------------------------------------------|----------------------------------------| +| No notification (Note) | Semi-permanent | User demand | Customized, Identified | +| | | Semi-permanent | Customized, Identified | +| | Switched | User or Network, after layer 1 activation by the user | Customized, Identified, Non-identified | +| Conditional notification | Semi-permanent | Originator demand | Customized, Identified | +| | Switched | Originator demand | Customized, Identified, Non-identified | +| NOTE – The definition of notification classes given in Recommendation X.31 [9] does not precise whether semi-permanent B-channels are concerned in combination with the “conditional notification” class. However, the three possibilities of B-channel layer 2 activation have to be considered. | | | | + +### B.2.3 Access of X.25 packet services over the D-channel (X.31 Case B) + +Table B.3 shows the valid parameter combinations to access X.25 [8] packet services over the D-channel. + +TABLE B.3/T.103 + +#### Parameter combinations for D-channel services + +| Notification class | Layer 2 activation | TEI allocation | X.25 packet service types | +|--------------------------|--------------------|----------------|----------------------------------------| +| No notification | Semi-permanent | Fixed TEI | Customized, Identified | +| | Originator demand | Fixed TEI | Customized, Identified | +| | Originator demand | Dynamic TEI | Customized, Identified, Non-identified | +| Conditional notification | Originator demand | Dynamic TEI | Customized, Identified, Non-identified | + +## B.3 Case selection for communication establishment + +### B.3.1 Outgoing calls + +The different parameters that may influence the choice of an access case among the three possibilities of Recommendation X.31 [9] are summarized in Table B.4. + +TABLE B.4/T.103 + +**Selection of the access type for outgoing calls** + +| Case selection | | | | X.25 packet service access | | +|----------------|-----------------------------------|--------------------------|-------------------------------|----------------------------------|------------------------| +| Bearer service | Selected channel | | Called address | Access case | Coordination function | +| | Type | Selected by | | | | +| Circuit mode | Semi-permanent B-channel (Note 1) | User | X.25 | X.31 Case A, (Note 2) | None | +| Packet mode | Semi-permanent B-channel (Note 1) | User | X.25 | X.31 Case B, B-channel | None | +| Circuit mode | Idle B-channel | User or Network (Note 3) | ISDN and X.25 (Note 4) | X.31 Case A or DTE/DTE, (Note 5) | Subclause 6.1 or T.102 | +| Packet mode | Idle B-channel (Note 3) | User or Network | X.25 (Note 6) | X.31 Case B, B-channel | Subclause 7.1 | +| Circuit mode | On demand established B-channel | User | ISDN and X.25 (Notes 4 and 7) | X.31 Case A or DTE/DTE, (Note 5) | None | +| Packet mode | On demand established B-channel | User | X.25 | X.31 Case B, B-channel | None | +| Packet mode | D-channel | User | X.25 | X.31 Case B, D-channel | None | + +NOTES + +- 1 The two semi-permanent B-channel types as defined in clause 6/X.31 [9] are included here (see also Figure B.1). If the B-channel is not established at this moment, the BIS provider will respond with a BIS-N-DISCONNECT indication to the BIS user. +- 2 Semi-permanent B-channels are excluded in the DTE/DTE case. +- 3 The call procedures used by the coordination function allow B-channel negotiation with the network. +- 4 The ISDN address is the one of the AU or the remote ISDN DTE. This address may be absent in case of a hot line (direct call). The X.25 address may be absent if the B-channel is connected to a remote ISDN DTE. +- 5 More parameters may be required to determine which interface can be used. +- 6 Although Recommendation Q.931 [7] call procedures are used, there is no need for an ISDN address. +- 7 The ISDN address has been used to establish the B-channel and is not required for a new virtual circuit establishment. + +NOTE – Where relevant, the access DTE/DTE case is also indicated for information. + +The reception of a BIS-N-CONNECT request primitive by layer 3 requires a channel selection: + +This selection is performed by the user. Nevertheless, the user may offer the network to select a B-channel among the idle ones when using the Recommendation Q.931 [7] procedures to establish this B-channel. + +When using the Recommendation Q.931 [7] procedures, a coordination function is required to establish a layer 1 B-channel before using the X.25 [8] protocols. + +When an already established B-channel (either semi-permanent or on demand) is selected, or when the D-channel is selected, the type of interface is determined by the parameters associated to this channel. + +Whereas, when establishing a new B-channel, the mode of operation depends on the network bearer service requested, i.e. circuit mode or packet mode. If circuit mode bearer service is selected, the ISDN end-system needs to know the characteristics of the ISDN end-system to be called: Access Unit (Case A). + +When requesting a bearer service on a B-channel, the network, even if it does not support this bearer service, will reply using the Recommendation Q.931 [7] procedures to indicate whether the operation is successful or not. Whereas, when requesting the packet mode bearer service on the D-channel, the network may not reply. + +The method by which the access type is determined is a local matter and is outside the scope of this Recommendation. + +### B.3.2 Incoming calls + +Tables B.5 and B.6 summarize the possible selections of interface types in case of incoming calls when the user has subscribed to the “No notification” class or the “Conditional notification” class, respectively. These tables take the three possibilities of Recommendation X.31 [9] interfaces and the DTE/DTE interface into account. + +TABLE B.5/T.103 + +#### Selection of the access type for incoming calls in the “No notification” class + +| Case selection | | | X.25 packet service access | | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------|-----------------------------|----------------------------------------|-----------------------| +| Bearer service | Selected channel | | Interface type | Coordination function | +| | Type | Originator | | | +| Circuit mode | Semi-permanent B-channel
(Notes 1 and 2) | AU | X.31 Case A
(Note 3) | None | +| Packet mode | Semi-permanent B-channel
(Notes 1 and 2) | Network | X.31 Case B
B-channel | None | +| Circuit mode | On demand established B-channel | Network or AU | X. 31 Case A or
DTE/DTE
(Note 4) | None | +| Packet mode | On demand established B-channel | Network or AU | X.31 Case B
B-channel | None | +| Circuit mode | Idle B-channel | Network or user
(Note 5) | DTE/DTE | T.102 | +| Packet mode | D-channel | Network | X.31 Case B
D-channel | None | +|

NOTES

1 The two semi-permanent B-channel types defined in clause 6/X.31 [9] are included here (see also Figure B.1).

2 The ISDN shall maintain the physical layer of the B-channel. If not established when the incoming call arrives, the AU/PH may clear this incoming call. Activation of layer 2 on the B-channel is made as indicated in Table B.2.

3 Semi-permanent B-channels are excluded in the DTE/DTE case.

4 The interface type of this B-channel has been determined when establishing it for the first outgoing/incoming call.

5 The call procedures of Recommendation Q.931 [7] allow a B-channel negotiation between the network and the user only for “point to point” configurations, either basic or primary rate access. For a basic rate access in “multi-point” configuration the network only selects the B-channel.

| | | | | + +TABLE B.6/T.103 + +## Selection of the access type for incoming calls in the “Conditional notification” class + +| Case selection | | | X.25 packet service access | | +|----------------|-----------------------------------|--------------------------|---------------------------------|------------------------| +| Bearer service | Selected channel | | Interface type | Coordination function | +| | Type | Originator | | | +| Circuit mode | Semi-permanent B-channel (Note 1) | AU | X.31 Case A (Note 2) | None | +| Packet mode | Semi-permanent B-channel (Note 1) | Network | X.31 Case B B-channel | None (Note 3) | +| Circuit mode | On demand established B-channel | Network or AU | X.31 Case A or DTE/DTE (Note 4) | None | +| Packet mode | On demand established B-channel | Network or user (Note 5) | X.31 Case B B-channel (Note 4) | Subclause 7.1 (Note 2) | +| Circuit mode | Idle B-channel | Network or user (Note 6) | X.31 Case A or DTE/DTE (Note 7) | Subclause 6.1 or T.102 | +| Packet mode | Idle B-channel | Network or user (Note 6) | X.31 Case B B-channel (Note 7) | Subclause 7.1 | +| Packet mode | D-channel | Network or user (Note 5) | X.31 Case B D-channel | None (Note 5) | + +NOTES + +1 The two semi-permanent B-channel types defined in clause 6/X.31 [9] are included here, but the definition of the “Conditional notification” class may not concern semi-permanent B-channel. Activation of layer 2 on the B-channel is made as indicated in Table B.2. + +2 Semi-permanent B-channels are excluded in Recommendation T.102. + +3 Networks conforming to Recommendation X.31 [9] do not offer the possibility of selecting a semi-permanent B-channel with the signalling procedures of the D-channel. This possibility is under study within CCITT study groups. + +4 The interface type of this B-channel has been determined when establishing it for the first outgoing/incoming call. + +5 Call offering procedures allow the user to select an already established B-channel or the D-channel, even in “multi-point configuration”. If no call offering procedures are used, then the network only shall select the channel, and no coordination function is required. + +6 The call procedures of Recommendation Q.931 [7] allow a B-channel negotiation between the network and the user only for “point to point” configurations, either basic or primary rate access. For a basic rate access in “multi-point” configuration, the network only selects the B-channel. + +7 The call set-up message may give some information on the calling ISDN system (i.e. AU or remote DTE). + +The BIS-N-CONNECT indication will always be issued to the BIS user on the reception of an incoming call packet. + +When no coordination function is required to receive the incoming call packet, the interface type is selected by the ISDN or the remote ISDN end-system (AU or DTE) and is already available within the called ISDN end-system. + +If the ISDN end-system does not support D-channel packet handling, it may not respond to a network request (SABME with SAPI = 16). + +When the ISDN requires coordination with call procedures of Recommendation Q.931 [7] or Recommendation X.31 [9], the following steps have to be performed: + +- *Compatibility checking of the SETUP message* – The Recommendation Q.931 [7] NL entity shall check the contents of the information elements in the SETUP message (especially Called party number or Called party sub-address, BC and LLC) with the possibilities of the ISDN end-system. + +NOTE – The ISDN uses this compatibility checking to select a TE1 in a “multi-point configuration”. + +- *Interface type selection* – Once the SETUP is acceptable, further investigations may be required to be able to send the CONNECT message to the network. These may include channel selection between B-channel or D-channel, between idle or established B-channels, or the determination whether the SETUP has been sent by an AU or a remote ISDN DTE. This selection, which may use the contents of information elements such as called/calling party number/sub-address, is, however, a local matter and is outside the scope of this Recommendation. + +NOTE – Under certain conditions (e.g. interworking with PSTN), the ISDN called system may confuse a remote ISDN calling DTE with a calling AU, and, as a consequence, accept the incoming call as an X.31 Case A interface. Since data link addresses (A/B) are not compatible, the layer 2 activation on the B-channel will not succeed in this case. + +- *Coordination between Recommendation Q.931 [7] procedures and X.25 [8] procedures* – After successful completion of Recommendation Q.931 [7] procedures, the procedures for X.25 [8] layers 2 and 3 shall apply. + +When an ISDN end-system has subscribed to the “No notification” class, a coordination function is never required, except for the case that a SETUP message has been received from a remote DTE. + +When an ISDN end-system has subscribed to the “Conditional notification” class, a coordination function will be required by the network to select a channel or a TE1 among those of a multi-point configuration, or will be required by a remote DTE to establish a new B-channel. + +If the network cannot transmit the incoming call packet while using the call offering procedures of Recommendation Q.931 [7] or Recommendation X.31 [9], because no B-channel is available, the BIS user of the called ISDN end-system is not informed of this attempt to establish a communication. + +## **Annex C** (informative) + +### **End-to-end system configurations** + +(This annex does not form an integral part of this Recommendation) + +#### **C.1 Introduction** + +The protocols and usage of supplementary services as specified in this Recommendation shall satisfy the requirements of Recommendation T.105 [5] defining the end-to-end protocols for the syntax-based Videotex service. + +The purpose of this annex is to clarify possible end-to-end environments in terms of the networks and the different types of end-systems concerned. + +#### **C.2 Network configurations** + +The scope of this Recommendation implies that at least one end of the communication is on an ISDN. The usage of packet mode may involve PSPDN in many communications. + +An ISDN may interwork with a PSPDN in different ways: + +- via an Access Unit (AU) to the PSPDN; +- via an interworking function between the packet mode bearer service in the ISDN and a PSPDN. + +Figures C.1 to C.7 illustrate some different configurations that may be used between two end-to-end Videotex systems. + +![Diagram of Circuit mode ISDN showing End system 1 connected to an ISDN circuit mode unrestricted digital data transfer block, which is then connected to End system 2.](38cbce07f83fba6d5a7c46605bd5743f_img.jpg) + +End system 1 — [ ISDN +circuit mode +unrestricted +digital data +transfer ] — End system 2 + +T0818440-94/d04 + +Diagram of Circuit mode ISDN showing End system 1 connected to an ISDN circuit mode unrestricted digital data transfer block, which is then connected to End system 2. + +FIGURE C.1/T.103 +**Circuit mode ISDN** + +![Diagram of Packet mode ISDN showing End system 1 connected to an ISDN PH block with a 3-2-1 structure, which is then connected to End system 2.](ec3647789b5c38fb686f2a0833324e79_img.jpg) + +End system 1 — [ ISDN +PH +3-3 +2-2 +1-1 ] — End system 2 + +T0818450-94/d05 + +Diagram of Packet mode ISDN showing End system 1 connected to an ISDN PH block with a 3-2-1 structure, which is then connected to End system 2. + +FIGURE C.2/T.103 +**Packet mode ISDN** + +![Diagram of Circuit mode ISDN to circuit mode ISDN showing End system 1 connected to an ISDN circuit mode unrestricted digital data transfer block, then to a PSPDN block with two AU units, and finally to another ISDN circuit mode unrestricted digital data transfer block, which is connected to End system 2.](7fe5741e83bc9702d1b1d7585ddf66bd_img.jpg) + +End system 1 — [ ISDN +circuit mode +unrestricted +digital data +transfer ] — [ PSPDN +AU AU ] — [ ISDN +circuit mode +unrestricted +digital data +transfer ] — End system 2 + +T0818460-94/d06 + +Diagram of Circuit mode ISDN to circuit mode ISDN showing End system 1 connected to an ISDN circuit mode unrestricted digital data transfer block, then to a PSPDN block with two AU units, and finally to another ISDN circuit mode unrestricted digital data transfer block, which is connected to End system 2. + +FIGURE C.3/T.103 +**Circuit mode ISDN to circuit mode ISDN** + +![Diagram of Packet mode ISDN to packet mode ISDN connection.](12c19090355e19922e23044633b9d1ea_img.jpg) + +The diagram illustrates a connection between two end systems via packet mode ISDN. On the left, 'End system 1' is connected to an ISDN PH (Primary Rate Interface) block, which is a 3x3 grid with values 3, 2, 1 in both rows and columns. This is followed by an IWF (ISDN-to-PSPDN Interface Function) block. The connection then enters the PSPDN (Packet Switched Public Data Network). On the right, the connection passes through another IWF block and another ISDN PH block (identical 3x3 grid) to reach 'End system 2'. The reference T0818470-94/d07 is located at the bottom right. + +Diagram of Packet mode ISDN to packet mode ISDN connection. + +FIGURE C.4/T.103 +Packet mode ISDN to packet mode ISDN + +![Diagram of Circuit mode ISDN to packet mode ISDN or vice-versa connection.](01e00200a536673d6cd0e6d8705047a0_img.jpg) + +The diagram shows a connection between two end systems via circuit mode ISDN. 'End system 1/2' is connected to an ISDN circuit mode unrestricted digital data transfer block. This is followed by an AU (Adaptation Unit) block, then the PSPDN, and another AU block. The connection then passes through an IWF block and an ISDN PH block (3x3 grid) to reach 'End system 2/1'. The reference T0818480-94/d08 is at the bottom right. + +Diagram of Circuit mode ISDN to packet mode ISDN or vice-versa connection. + +FIGURE C.5/T.103 +Circuit mode ISDN to packet mode ISDN or vice-versa + +![Diagram of Circuit mode ISDN to PSPDN connection.](0f1767577a073167eb9628d72034e083_img.jpg) + +The diagram depicts a connection from 'End system 1' to 'End system 2'. The signal path goes from 'End system 1' through an ISDN circuit mode unrestricted digital data transfer block, then an AU block, and finally into the PSPDN before reaching 'End system 2'. The reference T0818490-94/d09 is at the bottom right. + +Diagram of Circuit mode ISDN to PSPDN connection. + +FIGURE C.6/T.103 +Circuit mode ISDN to PSPDN + +![Diagram of Packet mode ISDN to PSPDN connection.](4346261cc730a1eb683f35e4ce9deacf_img.jpg) + +The diagram shows a connection from 'End system 1' to 'End system 2'. The signal path starts at 'End system 1', goes through an ISDN PH block (3x3 grid), then an IWF block, and enters the PSPDN before reaching 'End system 2'. The reference T0818500-94/d10 is at the bottom right. + +Diagram of Packet mode ISDN to PSPDN connection. + +FIGURE C.7/T.103 +Packet mode ISDN to PSPDN + +### C.3 Types of interfaces at the two end-systems + +In the network configurations described in C.2, several types of interfaces have to be used by end-systems: + +- *Recommendation X.25* +The system has a permanent connection to a PSPDN. +- *DTE/DTE* +The system is connected to the ISDN and uses DTE/DTE protocols on the B-channel for packet data transfer. The B-channel is established on demand. +- *X.31 Case A* +The system is connected to the ISDN and uses DTE/DCE protocols on the B-channel for packet data transfer, the DCE is outside the ISDN. The B-channel is established permanently or on demand. +- *X.31 Case B/B-channel* +The system is connected to the ISDN and uses DTE/DCE protocols on the B-channel for packet data transfer. The DCE is inside the ISDN. The B-channel is established permanently or on demand. +- *X.31 Case B/D-channel* +The system is connected to the ISDN and uses DTE/DCE protocols on the D-channel for packet data transfer. The DCE is inside the ISDN. The link layer over the D-channel is established permanently or on demand. + +Table C.1 illustrates the interfaces which may be used at the two ends of a packet mode communication and the corresponding network configurations available. + +Except for the case of DTE/DTE, each side of the communication in Table C.1 handles the channel establishment (permanent or on demand) independently from the other side. + +TABLE C.1/T.103 + +**Interfaces at the two Videotex end-systems** + +| End-system 1 | End-system 2 | | | | | +|-------------------------------------------------------------------------------------------------------|----------------------|---------------------------|--------------------------|---------------------------|------------| +| | DTE/DTE
B-channel | X. 31 Case A
B-channel | X.31 Case B
B-channel | X. 31 Case B
D-channel | X.25 | +| DTE/DTE B-channel | Figure C.1
(Note) | – | – | – | – | +| X.31 Case A
B-channel | – | Figure C.3 | Figure C.5 | Figure C.5 | Figure C.6 | +| X.31 Case B
B-channel | – | Figure C.5 | Figure C.2
Figure C.4 | Figure C.2
Figure C.4 | Figure C.7 | +| X.31 Case B
D-channel | – | Figure C.5
Figure C.4 | Figure C.2
Figure C.4 | Figure C.2 | Figure C.7 | +| NOTE – This case is outside the scope of this Recommendation, and is treated in Recommendation T.102. | | | | | | + +### C.4 End-system characteristics + +The layer 7 protocol defined in Recommendation T.105 [5] has identified several entities to describe a communication model: + +- the terminal is connected to the Access Network via the Terminal Function (TF); +- the Videotex Service is connected to the Access Network via the Access Function (AF). + +As the Videotex protocol on layer 7 is not symmetrical, an end-system can work as a TF or an AF. If two terminals want to communicate, one should act as an AF. The structure of the Videotex service – Access Function and Host Function in the same place, Access Function within a Videotex Access Point, etc. – has no influence on the characteristics of the end-system. + +An end-system, whenever it acts as a TF or AF, can initiate the communication (calling) or respond to a call (called). + +Table C.2 illustrates the different possibilities of the end-systems, and, for each case, its preferred use. + +TABLE C.2/T.103 + +**End-system characteristics** + +| Characteristics | | Possibilities | | | | Preferences | | | | +|-------------------------------------------------------------------------------------------------------|-----------------------|---------------|--------|---------|--------|-------------|--------|---------|--------| +| Interface | Channel establishment | TF | | AF | | TF | | AF | | +| | | Calling | Called | Calling | Called | Calling | Called | Calling | Called | +| DTE/DTE B-channel | On demand | X | X | X | X | 1 | | | 1 | +| X.31 Case A B-channel | On demand | X | X | X | X | 2 | | | 1 | +| | Permanent | X | X | X | X | | | | 1 | +| X.31 Case B B-channel | On demand | X | X | X | X | 1 | | | | +| | Permanent | X | X | X | X | 2 | | | 1 | +| X.31 Case B D-channel | On demand | X | X | X | X | 1 | | | | +| | Permanent | X | X | X | X | 1 | | | 2 | +| X.25 | | X | | | X | | | | 1 | +| TF Terminal function
AF Access function
X Possible
1 Higher preference
2 Lower preference | | | | | | | | | | + +## Annex D + +(normative) + +### Additional provisions for Recommendation X.31 + +(This annex forms an integral part of this Recommendation) + +#### D.1 General + +The deviations (restrictions, additions, precisions) to Recommendation X.31 apply only in the context of this Recommendation. + +#### D.2 Subclause 2.2/X.31: Configuration for the ISDN virtual circuit service (Case B) + +Precision concerning the connection between the ET and the PH in Figure 2-3/X.31: + +- This connection is either on demand or semipermanent, but has no relevance for the user-network procedures. Only internal procedures between the ET and the PH are required. + +### **D.3 Subclause 3.2.3.2/X.31: Conditional notification class** + +This conditional notification class applies to both the B- and the D-channel incoming call offerings. In this case the network shall allocate incoming calls to a channel (D/B) using a network dependent algorithm. + +Some networks may also, on a user's profile basis, compare the sub-address and use call offering procedure only if the ISDN address differs from the ISDN address of the terminal with the active packet access channel. + +### **D.4 Subclause 3.2.3.3/X.31: Unconditional notification class** + +The unconditional notification class is not supported. + +### **D.5 Subclause 3.2.3.4/X.31: Information mapping from the X.25 incoming call packet to the Q.931 message** + +The unconditional notification class is not supported. + +### **D.6 Subclause 4.1/X.31: Terminal and interface selection** + +The Note does not apply. + +The transmission capability information is used in accordance to 3.2/Q.931. + +### **D.7 Subclause 6.1.1/X.31: Circuit-switched access to PSPDN services (Case A)** + +Table 6-1/X.31: + +- In the case of primary rate access (PRA), the field “channel indication” shall be “channel number”. The D-channel indicator shall be coded as following: + - 0 to indicate No; + - 1 to indicate Yes. + +The information transfer capability of the Bearer capability information element included in the SETUP message shall be set to “unrestricted digital information”. + +The user may specify the layer 1, layer 2 and layer 3 information transfer protocols not only in the Low layer compatibility element, but also in the Bearer capability information element in the SETUP message. + +### **D.8 Subclause 6.1.2.1/X.31: B-channel** + +Some networks may require the calling party number and calling party sub-address information elements to be included in the SETUP message to select a specific user profile. + +### **D.9 Subclause 6.2.1.2/X.31: Channel selection** + +The information transfer capability of the Bearer capability information element included in the SETUP message shall be set to “unrestricted digital information”. + +The AU may also specify the layer 1 (e.g. rate adaption), layer 2 (i.e. LAPW), and layer 3 (i.e. Recommendation Q.931) information transfer protocols in the Low layer compatibility information element or the Bearer capability information element in the SETUP message (see Annex L/Q.931 “Low layer information coding principles”). + +Table 6-2/X.31: + +- In the case of primary rate access (PRA), the field “channel indication” shall be “channel number”. The D-channel indicator shall be coded as following: + - 0 to indicate No; + - 1 to indicate Yes. + +## **D.10 Subclause 6.2.2.1/X.31: B-channel** + +Additional exceptions for the B-channel: + +- The procedures for channel selection are specified in Table 6-3/X.31. + +Table 6-3/X.31: + +NOTE – Public networks conforming this Recommendation do not offer the negotiation between B- and D-channel. Networks which do not support B-channel negotiation shall offer the incoming call by indicating either Bi Exclusive, No D-channel or No channel Exclusive, D-channel, in the SETUP message. + +- In the case of primary rate access (PRA), the field “channel indication” shall be “channel number”. The D-channel indicator shall be coded as following: + - 0 to indicate No; + - 1 to indicate Yes. + +## **D.11 Subclause 6.2.2.3.1/X.31: Channel selection through call offering** + +The layer 3 messages are defined in 3.2/Q.931. + +On the D-channel of a user access, for a given communication the same connection endpoint suffix (CES) value as the one used by the selected terminal during the signalling phase (SAPI s) shall be used for data transfer over the D-channel (using SAPI p). + +Note 2 shall not apply. + +The information transfer capability shall be set to “unrestricted digital information” in any case. + +The option by which, in 6.2.2.3.1/X.31 and 6.2.2.3.1/Q.931, the network may offer SAPI = 16 broadcast call offering procedures for providing and supporting Q.931 signalling procedures is not recommended. + +## **D.12 Subclause 6.2.2.3.2/X.31: Information element mapping** + +Table 6-4/X.31: + +- The A-bit is not supported. +- Except for the “calling/called address (extension)”, the corresponding information elements in the Q.931 SETUP message are not applicable. + +NOTE – The network will map bits 8 and 7 of the first octet of the “Called address extension” facility parameter field in the X.25 incoming call packet to the “Type of sub-address” field in octet 3 of the “Called party sub-address” information element in the Q.931 SETUP message, assuming that the X.25 incoming call packet is coded based on the 1988 version of Recommendation X.25. Therefore, the called user could notice that the received “Type of sub-address” might not be correct when the X.25 incoming call packet is coded based on the 1984 version of Recommendation X.25. + +## **D.13 Subclause 6.4.1/X.31: B-channel** + +The restart message in Case B can be related to the particular B-channel or to the whole interface. + +## **D.14 Subclause 7.3.2/X.31: Rate adaption** + +Item 1) is also applicable for rate adaption using circuit mode of operation (Case A) by using HDLC interframe flag stuffing. + +## **Annex E** + +(normative) + +### **Additional provisions for Recommendation Q.931** + +(This annex forms an integral part of this Recommendation) + +#### **E.1 General** + +The deviations (restrictions, additions, precisions) to Recommendation Q.931 apply only in the context of this Recommendation. + +The following provisions apply throughout Recommendation Q.931: + +- Information elements reserved in Recommendation Q.931 for national use may partly be already used by ETSI. Therefore the use should be avoided for other purposes. +- The information element or the message SEGMENT mentioned below is only required if the optional segmentation procedure defined in Annex K/Q.931 is implemented. +- The codeset 5 (see 4.5/Q.931) reserved for national use is already used by ETSI. Therefore the use should be avoided for other purposes. +- The codeset 6 (see 4.5/Q.931) was reserved originally for the local network and shall now be reserved for information elements specific to a national network (either public or private). + +#### **E.2 Subclause 2.1.2/Q.931: Network call states** + +This subclause refers to the call states at the network side of the interface. + +#### **E.3 Subclause 3.1/Q.931: Messages for circuit mode connection control** + +An additional message, SEGMENT (see Annex K/Q.931), is implemented. + +The length for the “Call reference” element is 2-3 octets. + +The “Display” element length is limited to the maximum length of 34 octets; its minimum length is 2 octets. + +The following information elements are not supported: + +- Signal; +- Feature activate; +- Feature indicate; +- Switchhook; +- Bearer capability; +- Repeat indicator. + +#### **E.4 Subclause 3.1.4/Q.931: CONNECT** + +An additional information element is implemented: + +| Information element | Reference | Direction | Type | Length | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|-----------|-------------|--------| +| Date/Time | 4.6 | n → u | O (Note 12) | 2-7 | +| NOTE 12 – Included by the network, e.g. dependent on the telecommunication service requested by the user, or as a subscription option, or as a network provider default option. | | | | | + +## **E.5 Subclause 3.1.8/Q.931: Information** + +Note concerning the keypad facility information element: + +The use of the “Keypad facility” information element in the network-to-user direction to convey supplementary service information as part of the keypad facility procedures is a network option. + +Note 6: + +Only the “Called party number” information element is included by the user to convey called party number information to the network during overlap sending. + +The phrase “if the user wants” in the second sentence of Note 6 does not apply. + +Note 9: + +Only the “Called party number” information element is included by the user to convey called party number information to the network during overlap sending. + +## **E.6 Subclause 3.1.16/Q.931: Setup** + +Note concerning the “Keypad facility” information element: + +The use of the “Keypad facility” information element in the network-to-user direction to convey supplementary service information as part of keypad invocation procedure is a network option. + +Note 9 and Note 14: + +Only the “Called party number” information element is included by the user to convey called party number information to the network. + +## **E.7 Subclause 3.2/Q.931: Messages for packet-mode access connection control** + +Note concerning the information element “Progress indicator”: + +It may be included in the event of interworking with private network. Public networks will ignore this information element. + +The information element “Display” has a minimum length of 2 octets and a maximum length of 34 octets. + +The information element “Channel identification” has a maximum length of 5 octets. + +The information element “Call reference” has a maximum length of 3 octets. + +The following information elements are not supported: + +- user-user; +- information rate; +- end-to-end transition delay; +- transit delay selection and indication; +- packet layer binary parameters; +- packet layer window size; +- packet size. + +The information elements “Called/Calling party number” each have a maximum length of 23 octets. + +Note concerning the information elements “Calling party number/sub-address”: + +Included in the user to network direction depending on the user/network identification requirements; included in the network-to-user direction if the network implements Recommendations X.25 and Q.931 information element mapping and provides indication to the called user of the calling sub-address. + +Note concerning the information element “Progress indicator”: + +It may be included in the event of interworking with a private network. Public networks will ignore this information element. + +Note concerning the information element “Bearer capability”: + +It is used to identify the ISDN packet mode bearer capability. + +In addition, RESTART, RESTART ACKNOWLEDGE and STATUS messages usable with the global call reference shall apply when the restart procedures are used. These messages are defined in 3.4/Q.931. + +#### **E.8 Subclause 3.4/Q.931: Messages used with the global call reference** + +The message “SEGMENT” is included. + +The information element “Display” has a maximum length of 34 octets. + +The information element “Call reference” has a maximum length of 3 octets. + +#### **E.9 Subclause 4.3/Q.931: Call reference** + +The length of the call reference value for the basic access shall be 1 octet and for the primary rate access 2 octets. + +The call reference flag also applies to functions which use the global call reference (e.g. restart procedures). + +For the use of the global call reference value, see the restart procedure described in 5.5. + +The dummy call reference shall not be used in association with the basic call. In this context, the second sentence of Note 1 does not apply. + +#### **E.10 Subclause 4.4/Q.931: Message type** + +When allocating codes for national message types, the following principle shall be applied for the first octet following the escape to nationally specific type: + +1 0 x x x x x National standard, + +1 x x x x x x ETSI standard. + +#### **E.11 Subclause 4.5/Q.931: Other information elements** + +The following information elements are not supported: + +- Repeat indicator; +- Switchhook; +- Feature activation; +- Feature indication. + +The maximum length of the “Display” information element is restricted to 34 octets. + +The “Called/Calling party number” information element length is network dependent. + +The following information elements may not be repeated: + +- Bearer capability; +- Low layer compatibility; +- High layer compatibility. + +#### **E.12 Subclause 4.5.1/Q.931: Coding rules** + +NOTE – One of the single octet formats is specified for shift operations described in 4.5.2. This allows for the definition of eight codesets of 133 information element identifier values in each. Codeset 0 is used for these information elements that have been specified in this Recommendation. For codeset 5, see general remarks above. + +### **E.13 Subclause 4.5.2/Q.931: Extension codesets** + +The information element identifier code points with bits 5 to 8 coded “0000” in each of the codesets are reserved for information elements for which comprehension by the receiver is required (see 5.8.7.1/Q.931 for specific error handling procedures). + +### **E.14 Subclause 4.5.5/Q.931: Bearer capability** + +The following values are not applicable in ISDNs conforming to this ETS: + +- Information transfer capability (octet 3): +“restricted digital information”. +- Structure (octet 4a): +transfer mode: circuit +transfer capability: restricted digital +structure: 8 kHz integrity. +- User information layer 1 protocol (octet 5): +Recommendation G.711 $\mu$ -law +CCITT standardized rate adaption V.120. +- Octet 5b for V.120 rate adaption. + +### **E.15 Subclause 4.5.6/Q.931: Call identity** + +The maximum length of this information element is always 10 octets. + +### **E.16 Subclause 4.5.7/Q.931: Call state** + +The purpose of the “Call state” information element is not to describe an access connection. + +### **E.17 Subclause 4.5.8/Q.931: Called party number** + +The maximum length of this information element is 23 octets. + +Note concerning the information element “Abbreviated number”: + +NOTE – The support of this code is network dependent. The number provided in this information element presents a shorthand representation of the complete number in the specified numbering plan as supported by the network. + +### **E.18 Subclause 4.5.9/Q.931: Called party sub-address** + +NOTE – When the initial domain identifier (IDI) format is “local”, the AFI field is coded “50” in BCD. IA5/ISO646 character syntax DSP is then represented by converting each character to a number in the range 32-127 using the T.50/ISO646 encoding, with zero parity and the parity bit in the most significant position, yielding a binary octet in the range 0010 0000-0111 1111. + +NOTE – It is recommended that users apply the local IDI format when the sub-address is used for terminal selection purposes. In this case the IA5 character syntax using only digits 0 to 9 shall be used for the DSP. + +### **E.19 Subclause 4.5.10/Q.931: Calling party number** + +The information element “Abbreviated number” is not applicable. + +The “Screening indicator”: “user-provided, verified and failed” is not applicable. + +### **E.20 Subclause 4.5.11/Q.931: Calling party sub-address** + +The additional Notes in E.18 apply. + +## **E.21 Subclause 4.5.13/Q.931: Channel identification** + +The following codepoints or values are not applicable in ISDNs conforming to this ETS: + +- “Interface identifier present”: +interface explicitly defined; +- “Interface identifier”; +- “Number/map”: +channel is indicated by the slot map; +- “Slot map”. + +The use of the following codepoints is restricted in ISDNs conforming to this ETS: + +- “Interface type”: This codepoint is only applied for the primary rate interface. +- “Channel number”: Channel number is used exclusively. + +## **E.22 Subclause 4.5.15/Q.931: Display** + +The display information element has a maximum length of 34 octets. + +The IA5 character string in the “Display” field shall be coded using appropriate national IA5 tables. + +## **E.23 Subclause 4.5.16/Q.931: High layer compatibility** + +These information elements are coded as below in ISDNs conforming to this ETS: + +*High layer characteristics identification (octet 4):* + +Bits + +7654321 + +- 0000001 Telephony +- 0000100 Facsimile Group 2/3 (Recommendation F.182) +- 0100001 Facsimile Group 4, class I (Recommendation F.184) +- 0100100 Teletex service, basic and mixed mode of operation (Recommendation F.230) and facsimile service Group 4, classes II and III (Recommendation F.184) +- 0101000 Teletex service, basic and processable mode of operation (Recommendation F.220) +- 0110001 Teletex service, basic mode of operation (Recommendation F.200) +- 0110010 International interworking for Videotex services (Recommendations F.300 and T.101) +- 0110101 Teletex service (Recommendation F.60) + +*Extended high layer characteristics identification (octet 4a):* + +Bits + +7654321 + +- 0000001 Telephony +- 0000100 Facsimile Group 2/3 (Recommendation F.182) +- 0100001 Facsimile Group 4, class I (Recommendation F.184) +- 0100100 Teletex service, basic and mixed mode of operation (Recommendation F.230) and facsimile service Group 4, classes II and III (Recommendation F.184) +- 0101000 Teletex service, basic and processable mode of operation (Recommendation F.220) +- 0110001 Teletex service, basic mode of operation (Recommendation F.200) +- 0110010 International interworking for Videotex services (Recommendation F.300 and T.101) +- 0110101 Teletex service (Recommendation F.60) + +## **E.24 Subclause 4.5.18/Q.931: Low layer compatibility** + +The octet 3a shall be present if out-band negotiation is required. + +The “Modem type” information element is coded as below for ISDNs conforming to this Recommendation: + +*Modem type (octet 5d):* + +Bits + +654321 + +000000 Reserved + +000001 V.21 + +000010 V.22 + +000011 V.22 *bis* + +000100 V.23 + +000101 V.26 + +000111 V.26 *bis* + +001000 V.26 *ter* + +001001 V.27 + +001010 V.27 *bis* + +001011 V.27 *ter* + +001100 V.32 + +001101 V.35 + +| | | | +|---------|---|----------------------------| +| 100000 | } | Reserved for national use. | +| through | | | +| 111111 | | | + +All other values are reserved. + +The following information elements are user specified: + +- Optional layer 2 protocol information (octet 6a); +- Optional layer 3 protocol information (octet 7a). + +## **E.25 Subclause 4.5.21/Q.931: Notification indicator** + +The notification description information element “Bearer service change” is not applicable. + +## **E.26 Subclause 4.5.23/Q.931: Repeat indicator** + +This information element is not used. + +## **E.27 Subclause 4.5.24/Q.931: Restart indicator** + +Since this Recommendation applies only to associated signalling, the “Channel identification” information element shall not be included to indicate the interface to be restarted. As a consequence, either code point can be used to perform the same function. + +## **E.28 Subclause 4.7.6/Q.931: Redirecting number** + +The maximum length of this information element is network dependent. However it shall not exceed 25 octets. + +“Type of Number” (octet 3): “abbreviated number” is not applicable. + +“Screen indicator” (octet 3a): “user provided, verified and failed” is not applicable. + +### **E.29 Subclause 5.1.1/Q.931: Call request** + +The dummy call reference value is not supported in association with the basic call. + +In the case of *en-bloc* sending, item b) does not apply. + +If *en-bloc* sending is used, the SETUP message may contain the sending complete indication (i.e. either the “Sending complete” information element or the “#” character within the “Called party number” information element). It is mandatory for the network to recognize the “Sending complete” information element. + +Called party sub-address information, if present, shall be given in the “Called party sub-address” information element and, in the case of overlap sending, shall only be sent in the SETUP message. + +### **E.30 Subclause 5.1.2/Q.931: B-channel selection – Originating** + +It is recommended that TEs connected to the ISDN basic access should use alternative c) for basic circuit-switched call control unless the TE is already using a given B-channel. + +The selected B-channel is indicated in the “Channel identification” information element coded as “channel is indicated, no acceptable alternative”. + +### **E.31 Subclause 5.1.8/Q.931: Call connected** + +Upon receiving an indication that the call has been accepted, the network shall remove any applied ringing tone. + +### **E.32 Subclause 5.2/Q.931: Call establishment at the destination interface** + +The second paragraph shall read: + +Data link connections may be established by the TA, TE or NT2 as soon as a TEI is assigned (either locally or by automatic assignment procedure), and may be retained indefinitely. This may be recommended as a network option. + +### **E.33 Subclause 5.2.1/Q.931: Incoming call** + +The knowledge that a single-point configuration exists may be based on information entered at the time of configuration of the access. + +For procedures to be followed on expiry of timer T312, see also 5.2.5.3/Q.931 (Case 1). + +### **E.34 Subclause 5.2.3.1/Q.931: SETUP message delivered by point-to-point data link** + +Item a): + +All ISDNs conforming to this Recommendation will support the “no B-channels available” condition. + +Item b): + +In Case 2) the channel is identified in the Channel identification information element as “channel is indicated, no acceptable alternative”. + +Item e): + +See 5.2.4/Q.931 and 5.2.5/Q.931 for the appropriate first response to the SETUP message. + +### **E.35 Subclause 5.2.6/Q.931: Notification of interworking at the terminating interface** + +If the “Progress indicator” information element is included in the PROGRESS message, it is assumed that ISDNs will stop any supervisory timer except network timers T304 and T312. + +### **E.36 Subclause 5.2.4/Q.931: Overlap receiving** + +If a “sending complete” indication is provided, the “Sending complete” information element shall be used. + +#### **E.37 Subclause 5.2.7/Q.931: Call accept** + +The Note does not apply. + +#### **E.38 Subclause 5.3.3/Q.931: Clearing initiated by the user** + +The actions to be taken with regard to the maintenance condition are network dependent. + +#### **E.39 Subclause 5.3.4.3/Q.931: Completion of clearing** + +The option of placing the B-channel in the maintenance condition is not applicable in the case of point-to-multipoint configurations. + +#### **E.40 Subclause 5.3.5/Q.931: Clear collision** + +“Call reference value” shall be replaced by “Call”. + +In the last sentence, “if appropriate” shall be removed. + +#### **E.41 Subclause 5.5/Q.931: Restart procedure** + +The restart procedure may also be initiated as a result of local failure, maintenance action or misoperation. + +#### **E.42 Subclause 5.5.1/Q.931: Sending RESTART** + +Also, no further RESTART messages shall be sent until a RESTART ACKNOWLEDGE message is received or timer T316 expires. + +If a RESTART ACKNOWLEDGE message is received indicating only a subset of the specified channels, an indication shall be given to the maintenance entity to determine what actions shall be taken on the channel(s) which have not been returning to the idle condition. + +#### **E.43 Subclause 5.5.2/Q.931: Receipt of RESTART** + +Note 2 (changed) – The receiving entity shall return to the Null state only those Q.931 calls which are: + +- a) associated with the data link connection endpoint identifier (DLCI; see Recommendation Q.920); and +- b) which correspond to the specified channel(s) or interface. + +If only a subset of the specified channels have been returned to the idle condition when timer T317 expires, a RESTART ACKNOWLEDGE message should be transmitted to the originator, containing a “Channel identification” information element indicating the channel(s) that have been returned to the idle condition. + +The following entities shall be released: + +- a) B-channels established by Q.931 messages including channels used for packet access (Case B) (consequently all virtual calls carried in the released channel(s) will be handled as described in 6.4.1); +- b) user signalling bearer service connections. + +The following entities shall not be released: + +- a) semi-permanent connections that are established by man-machine commands; +- b) entities associated with any other DLCI. + +If semi-permanent connections established by man-machine commands are implicitly specified (by specifying “single interface” or “all interfaces”), no action shall be taken on those channels but a RESTART ACKNOWLEDGE message shall be returned containing the appropriate indications (i.e. “single interface” or “all interface”). + +If semi-permanent connections established by man-machine commands are explicitly specified (by including a “Channel identification” information element in the RESTART message), no action shall be taken on those channels and a STATUS message shall be returned with cause #82 “identification channel does not exist” optionally indicating in the diagnostic field the channel(s) that could not be handled. + +#### **E.44 Subclause 5.6/Q.931: Call rearrangements** + +The use of the call rearrangement procedure is restricted to basic access, i.e. it will not be available for primary rate access. For call rearrangements controlled by an NT2, see 5.6.7/Q.931. + +#### **E.45 Subclauses 5.6.1/Q.931 and 5.6.2/Q.931: Call suspension/suspended** + +Some networks may only support a maximum length of the call identity value of two octets. + +#### **E.46 Subclause 5.6.3/Q.931: Call suspend error** + +If the network does not support the call rearrangement procedures, it shall reject a SUSPEND message according to the error handling procedures of 5.8.4/Q.931. If the network supports the call rearrangement procedures on a subscription basis, but the user does not subscribe to the service, the network shall reject a SUSPEND message by sending a SUSPEND REJECT message with cause #50 “request facility not subscribed”; the “Cause” information element shall not contain a diagnostic field under these circumstances. + +#### **E.47 Subclause 5.6.4/Q.931: Call re-establishment** + +Some networks may not support the use of the NOTIFY message. + +No compatibility checking is performed during the call re-establishment phase. + +#### **E.48 Subclause 5.6.5/Q.931: Call resume errors** + +If the network does not support the call rearrangement procedures, it may reject a RESUME message according to the error handling procedures of 5.8.3.2 a)/Q.931. For this purpose, the RESUME message would be deemed to be an unrecognized message. + +#### **E.49 Subclause 5.8.3.1/Q.931: Invalid call reference format** + +When a message associated with the basic call is received specifying the dummy call reference, this message shall be ignored. + +#### **E.50 Subclause 5.8.3.2/Q.931: Call reference procedural errors** + +Item a): + +RESUME applies in this context for networks supporting the call rearrangement procedures of 5.6/Q.931. + +#### **E.51 Subclause 5.8.5/Q.931: General information element errors** + +The use of the locking or non-locking shift procedures in the diagnostic field of the “Cause” information element only applies to the interpretation of the information element identifiers of the information elements in codesets other than 0 without any impact on the interpretation of the information element itself. + +#### **E.52 Subclause 5.8.7.2/Q.931: Non-mandatory information element content error** + +The “Call identity” information element will have a special treatment and will be truncated and processed in the case that it exceeds the maximum length implemented. + +### **E.53 Subclause 5.8.9/Q.931: Data link failure** + +This clause should read as follows: + +Whenever a Q.931 entity is notified by its data link entity via the DL-RELEASE-INDICATION primitive that there is a data link layer malfunction, the following procedure shall apply: + +- a) Any calls not in the Active states shall be cleared internally. +- b) For any call in the Active state, timer T309 shall be started (if implemented). + +If timer T309 is already running, it shall not be restarted. + +The Q.931 entity shall request layer 2 re-establishment by sending a DL-ESTABLISH-REQUEST primitive. + +When informed of layer 2 re-establishment by means of the DL-ESTABLISH-CONFIRM primitive, the following procedure shall apply: + +- 1) stop timer T309; +- 2) a STATUS message with cause #31, "normal, unspecified" shall also be sent to report the current call state to the peer entity. Alternatively, a STATUS ENQUIRY message may be sent to verify the call state of the peer entity. + +If timer T309 expires prior to data link re-establishment, the network shall clear the network connection and call to the remote user with cause #27 "destination out of order", disconnect and release the B-channel, release the call reference and enter the Null state. + +If timer T309 expires prior to data link re-establishment, the user shall clear an attached connection (if any) with cause #27 "destination out of order", disconnect and release the B-channel, release the call reference and enter the Null state. + +The implementation of timer T309 in the user side is optional, and in the network side is mandatory. + +### **E.54 Subclause 5.8.10/Q.931: Status enquiry procedure** + +Cause #30 shall be used when the status enquiry procedure is implemented. + +### **E.55 Annex B/Q.931: Compatibility checking** + +"DDI" shall be removed. + +"DDI number" shall be replaced by "assigned number". + +B.3.4/Q.931: User action tables + +"DDI" shall be replaced by "the appropriate part of the called party number". + +## **Annex F** (normative) + +### **Information elements for the control of packet-mode access connections** (This annex forms an integral part of this Recommendation) + +This annex lists the information elements used by packet-mode access connections control procedures. + +#### **F.1 Protocol discriminator** + +Coded as specified by 4.2/Q.931 (see Figure 4.2/Q.931). + +#### **F.2 Call reference** + +The Call reference information element is managed and coded as defined by 4.3/Q.931. + +It is two octets long on the basic rate access and three octets long on the primary access. + +The Dummy call reference value shall not be used. + +The Global Call reference value is applicable only when the Restart procedure is used (see 5.5/Q.931). + +### F.3 Message type + +This information element is coded as defined by 4.4/Q.931. Table F.1 shows the coding of the message types applicable to the packet-mode access connections control procedures. + +TABLE F.1/T.103 + +#### Message types + +| 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | +|-----------------------------------------------------------------------------------------------------------------------------|---|---|---|---|---|---|---|---------------------------------------------------------------| +|
| | | | | | | | | +| 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | Escape to nationally specific message type
(Notes 1 and 2) | +| 0 | 0 | 0 | - | - | - | - | - | Access connection establishment messages: | +| | | | 0 | 0 | 0 | 0 | 1 | – ALERTING | +| | | | 0 | 0 | 0 | 1 | 0 | – CALL PROCEEDING | +| | | | 0 | 0 | 1 | 1 | 1 | – CONNECT | +| | | | 0 | 1 | 1 | 1 | 1 | – CONNECT ACKNOWLEDGE | +| | | | 0 | 0 | 0 | 1 | 1 | – PROGRESS | +| | | | 0 | 0 | 1 | 0 | 1 | – SETUP | +| 0 | 1 | 0 | - | - | - | - | - | Access connection clearing messages: | +| | | | 0 | 0 | 1 | 0 | 1 | – DISCONNECT | +| | | | 0 | 1 | 1 | 0 | 1 | – RELEASE | +| | | | 1 | 1 | 0 | 1 | 0 | – RELEASE COMPLETE | +| | | | 0 | 0 | 1 | 1 | 0 | – RESTART | +| | | | 0 | 1 | 1 | 1 | 0 | – RESTART ACKNOWLEDGE | +| 0 | 1 | 1 | - | - | - | - | - | Miscellaneous messages: | +| | | | 1 | 1 | 1 | 0 | 1 | – STATUS | +| | | | 1 | 0 | 1 | 0 | 1 | – STATUS ENQUIRY | +| NOTES | | | | | | | | | +| 1 When used, the message type is defined in the following octet(s), according to the national specification. | | | | | | | | | +| 2 When allocating codes for national message types, the following principle shall be applied for the first following octet: | | | | | | | | | +| 1 0 X X X X X X: National standard | | | | | | | | | +| 1 1 X X X X X X: ETSI standard. | | | | | | | | | + +### F.4 Other information elements + +The list of the information elements and the coding of the information element identifiers of codeset 0 and specific to each message are shown in Table F.2. + +TABLE F.2/T.103 +**Information element identifier coding** + +| | Q.931
(references) | Maximum length
(octets) | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------| +|
8 7 6 5 4 3 2
1
1 : : : - - - - Single octet information elements:
0 0 0 - - - - Reserved
0 0 1 - - - - Shift (Note)
0 : : : : : : : Variable length information elements:
0 0 0 0 1 0 Bearer capability
0 Cause
0 0 0 1 0 0
0 Call state
0 0 1 0 1 0
0 Channel identification
0 0 1 1 1 1 Progress indicator
0
1 1 0 1 1 0 Calling party number
0
1 1 0 1 1 0 Calling party sub-address
1
1 1 1 0 0 0 Called party number
0
1 1 1 0 0 0 Called party sub-address
1
1 1 1 0 1 0 Redirecting number
0
1 1 1 1 0 0 Restart indicator
1
1 1 1 1 1 1 Escape for extension
1
All other values are reserved.
|


4.5.3/4.5.4

4.5.5
4.5.12
4.5.7
4.5.13
4.5.22
4.5.10
4.5.11
4.5.8
4.5.9
F.6
4.5.24 |


1

7
32
3
5
4
24
23
23
23
25
3 | +| NOTE – This information element may appear more than once in a message. | | | + +Their coding rules are specified in 4.5.1/Q.931, the use of other codesets than codeset zero is defined in 4.5.2, and procedures for changing from one codeset to another are defined in 4.5.3 and 4.5.4. + +The codings of the information elements listed in Table F.2 are defined in Recommendation Q.931, as shown in the reference column, with the exception of the coding of the Redirecting number information element which is specified in F.6. + +#### NOTES + +- 1 The Bearer capability is coded with the attribute values defined in 6.1.2.1/X.31. It shall be 7 octets long. +- 2 The Cause information element shall only contain values defined in Table 4.13/Q.931. Octet 3a shall therefore not be used. If present, the Cause information element shall be treated according to error handling procedures defined in 5.8/Q.931. + +## F.6 Redirecting number + +The purpose of the redirecting number information element is to identify the number from which a call diversion or transfer was invoked. + +The redirecting number information element is coded as shown in Figure F.1 and Table F.3. + +The maximum length of this information element is network dependent. However, it shall not exceed 25 octets. + +![](fd8f5da2b60cdca94896f3cde8ee81f0_img.jpg) + +| | | | | | | | | | | +|---------------------------------------|-------------------------------------------------------------------------|---|----------------|------------------------|-------------------------------|---------------------|---|-----------|---| +| | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | | +| 0 |
Redirecting number
Information element identifier
| | | | | | | Octet 1 | | +| Length of redirecting number contents | | | | | | | | | 2 | +| 0/1
ext | Type of number | | | | Numbering plan identification | | | | 3 | +| 0/1
ext | Presentation indicator | | 0 0 0
Spare | | | Screening indicator | | 3a* | | +| 1
ext | 0 0 0
Spare | | | Reason for redirection | | | | 3b* | | +| 0
Spare | Number digits
(IA5 characters) | | | | | | | 4
etc. | | + +FIGURE F.1/T.103 + +Redirecting number information element + +TABLE F.3/T.103 + +Redirecting number information element + +| Type of number (octet 3) (Note 1) | | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------| +| Bits | | +| 7 6 5 | | +| 0 0 0 | Unknown (Note 2) | +| 0 0 1 | International number (Note 3) | +| 0 1 0 | National number (Note 3) | +| 0 1 1 | Network specific number (Note 4) | +| 1 0 0 | Subscriber number (Note 3) | +| 1 1 0 | Abbreviated number (Note 5) | +| 1 1 1 | Reserved for extension | +| All other values are reserved.
NOTES
1 For the definition of international, national and subscriber number, see Recommendation I.330 [5].
2 The type of number “unknown” is used when the user or the network has no knowledge of the type of number, e.g. international number, national number, etc. In this case the number digits field is organized according to the network dialling plan; e.g. prefix or escape digits might be present.
3 Prefix or escape digits shall not be included.
4 The type of number “network specific number” is used to indicate administration/service number specific to the serving network, e.g. used to access an operator.
5 This codepoint is not applicable to this Recommendation. | | + +TABLE F.3/T.103 (cont.) + +**Redirecting number information element** + +| Numbering plan identification (octet 3) | | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------| +| Bits | | +| 4 3 2 1 | | +| 0 0 0 0 | Unknown (Note) | +| 0 0 0 1 | ISDN/telephony numbering plan (Recommendations E.164 [2] and E.163 [1]) | +| 0 0 1 1 | Data numbering plan (Recommendation X.121) | +| 0 1 0 0 | Telex numbering plan (Recommendation F.69) | +| 1 0 0 0 | National standard numbering plan | +| 1 0 0 1 | Private numbering plan | +| 1 1 1 1 | Reserved for extension | +|

Numbering plan (applies for type of number = 000, 001, 010 and 100).

All other values are reserved.

NOTE – The numbering plan “unknown” is used when the user or the network has no knowledge of the numbering plan. In this case the number digits field is organized according to the network dialling plan, e.g. prefix or escape digits might be present.

| | + +| Presentation indicator (octet 3a) | | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------| +| Bits | | +| 7 6 | | +| 0 0 | Presentation allowed | +| 0 1 | Presentation restricted | +|

All other values are reserved.

NOTE – At the redirecting user-network interface, the presentation indicator is used for indicating the intention of the redirecting user for the presentation of the redirecting number to the called user. This may also be requested on a subscription basis. If octet 3a is omitted, and the network does not support subscription information for the redirecting number information restrictions, the value “00 presentation allowed” is assumed.

| | + +| Screening indicator (octet 3a) | | +|----------------------------------------------------------------------------|------------------------------------| +| Bits | | +| 2 1 | | +| 0 0 | User provided, not screened | +| 0 1 | User provided, verified and passed | +| 1 0 | User provided, verified and failed | +| 1 1 | Network provided | +| NOTE – If octet 3a is omitted “00 User provided, not screened” is assumed. | | + +TABLE F.3/T.103 (*end*) +**Redirecting number information element** + +| Reason for redirection (octet 3b) | | +|-----------------------------------|--------------------------------------------------------------| +| Bits
4 3 2 1 | | +| 0 0 0 1 | Call forwarding busy or called DTE busy | +| 0 0 1 0 | Called forwarding no reply | +| 1 0 0 1 | Called DTE out of order | +| 1 0 1 0 | Call forwarding by the called DTE | +| 1 1 1 1 | Call forwarding unconditional or systematic call redirection | +| All other values are reserved. | | + + + +| Number digit (octet 4, etc.) | +|--------------------------------------------------------------------------------------------------------------------------| +| This field is coded with IA5 characters, according to the formats specified in the appropriate numbering/ dialling plan. | + +## Annex G + +(informative) + +### References + +(This annex does not form an integral part of this Recommendation) + +- CCITT Rec. I.112 (1988) *Vocabulary of terms for ISDN.* +- CCITT Rec. T. 51 (1988) *Coded character sets for telematic services.* +- CCITT Rec. T. 90 *Characteristics and protocols for terminals for telematic services in ISDN.* +- CCITT Rec. X.29 *Procedures for the exchange of control information and user data between a packet assembly/disassembly (PAD) facility and a packet mode DTE or another PAD.* +- CCITT Rec. 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T.105 + +(Previously "CCITT Recommendation") + +--- + +# FOREWORD + +The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). + +ITU-T Recommendation T.105 was prepared by the ITU-T Study Group 8 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 11th of November 1994. + +# --- NOTE + +In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +© ITU 1995 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +# CONTENTS + +| | | Page | +|---|-------------------------------------------------------|-------------| +| 1 | Scope ..... | 1 | +| 2 | Normative references ..... | 1 | +| 3 | Definitions and abbreviations..... | 2 | +| | 3.1 Definitions ..... | 2 | +| | 3.2 Abbreviations..... | 3 | +| 4 | Overview ..... | 5 | +| | 4.1 Direct selection of Videotex Applications ..... | 5 | +| | 4.2 Multicommunication..... | 5 | +| | 4.3 Multimedia communication..... | 5 | +| | 4.4 Distributed Videotex Application..... | 5 | +| | 4.5 Supplementary services ..... | 6 | +| | 4.6 Handling of incoming calls..... | 6 | +| 5 | Configurations..... | 6 | +| 6 | General model ..... | 6 | +| | 6.1 Communication model..... | 6 | +| | 6.2 Terminal model..... | 8 | +| | 6.3 Protocol pillar ..... | 11 | +| 7 | Service definition ..... | 12 | +| | 7.1 Introduction ..... | 12 | +| | 7.2 Kernel services..... | 14 | +| | 7.2.1 SBV_Establish ..... | 14 | +| | 7.2.2 SBV_Release ..... | 16 | +| | 7.2.3 SBV_Reset..... | 17 | +| | 7.2.4 SBV_VTX_Data ..... | 18 | +| | 7.2.5 X.3 parameter manipulation services..... | 18 | +| | 7.2.5.1 SBV_Set_Param ..... | 18 | +| | 7.2.5.2 SBV_Read_Param ..... | 18 | +| | 7.2.5.3 SBV_Set_Read_Param ..... | 19 | +| | 7.2.5.4 SBV_Param_Ind ..... | 19 | +| | 7.2.6 SBV_TFI..... | 19 | +| | 7.2.7 SBV_TC_Error ..... | 20 | +| | 7.3 Optional services ..... | 20 | +| | 7.3.1 Communication channel management services ..... | 20 | +| | 7.3.1.1 SBV_Channel_Open ..... | 21 | +| | 7.3.1.2 SBV_Channel_Close ..... | 23 | +| | 7.3.1.3 SBV_Channel_Error ..... | 23 | +| | 7.3.2 Application selection services..... | 24 | +| | 7.3.2.1 SBV_Begin_Application ..... | 24 | +| | 7.3.2.2 SBV_End_Application ..... | 25 | +| | 7.3.2.3 SBV_End_Immediate ..... | 25 | +| | 7.3.3 Transparent processable data services ..... | 25 | +| | 7.3.3.1 SBV_TPD_Begin..... | 25 | +| | 7.3.3.2 SBV_TPD_End..... | 26 | +| | 7.3.4 SBV_DFK..... | 26 | +| | 7.3.5 SBV_Remote_Echo ..... | 27 | +| | 7.3.6 SBV_Escape ..... | 27 | + +| | Page | +|-------------------------------------------------------------------|-------------| +| 8 Protocol ..... | 28 | +| 8.1 Association of SBV Application Layer and BIS primitives ..... | 28 | +| 8.2 Procedures ..... | 29 | +| 8.2.1 SBV_Establish ..... | 29 | +| 8.2.2 SBV_Release ..... | 29 | +| 8.2.3 SBV_Reset ..... | 29 | +| 8.2.4 SBV_VTX_Data ..... | 29 | +| 8.2.5 X.3 parameter manipulation services ..... | 30 | +| 8.2.5.1 SBV_Set_Param ..... | 30 | +| 8.2.5.2 SBV_Read_Param ..... | 30 | +| 8.2.5.3 SBV_Set_Read_Param ..... | 30 | +| 8.2.5.4 SBV_Param_Ind ..... | 30 | +| 8.2.6 SBV_TFI ..... | 30 | +| 8.2.7 SBV_TC_Error ..... | 30 | +| 8.2.8 Communication channel management services ..... | 30 | +| 8.2.8.1 SBV_Channel_Open ..... | 30 | +| 8.2.8.2 SBV_Channel_Close ..... | 30 | +| 8.2.8.3 SBV_Channel_Error ..... | 31 | +| 8.2.9 Application selection services ..... | 31 | +| 8.2.9.1 SBV_Begin_Application ..... | 31 | +| 8.2.9.2 SBV_End_Application ..... | 31 | +| 8.2.9.3 SBV_End_Immediate ..... | 31 | +| 8.2.10 Transparent processable data services ..... | 31 | +| 8.2.10.1 SBV_TPD_Begin ..... | 31 | +| 8.2.10.2 SBV_TPD_End ..... | 31 | +| 8.2.11 SBV_DFK ..... | 31 | +| 8.2.12 SBV_Remote_Echo ..... | 31 | +| 8.2.13 SBV_Escape ..... | 31 | +| 8.3 Mapping of parameters ..... | 31 | +| 8.3.1 SBV_Establish ..... | 31 | +| 8.3.2 SBV_Release ..... | 31 | +| 8.3.3 SBV_Reset ..... | 33 | +| 8.3.4 SBV_VTX_Data ..... | 33 | +| 8.3.5 X.3 parameter manipulation services ..... | 33 | +| 8.3.5.1 SBV_Set_Param ..... | 33 | +| 8.3.5.2 SBV_Read_Param ..... | 34 | +| 8.3.5.3 SBV_Set_Read_Param ..... | 34 | +| 8.3.5.4 SBV_Param_Ind ..... | 34 | +| 8.3.6 SBV_TFI ..... | 34 | +| 8.3.7 SBV_TC_Error ..... | 35 | +| 8.3.8 Communication channel management services ..... | 35 | +| 8.3.8.1 SBV_Channel_Open ..... | 35 | +| 8.3.8.2 SBV_Channel_Close ..... | 36 | +| 8.3.8.3 SBV_Channel_Error ..... | 36 | +| 8.3.9 Application selection services ..... | 36 | +| 8.3.9.1 SBV_Begin_Application ..... | 36 | +| 8.3.9.2 SBV_End_Application ..... | 37 | +| 8.3.9.3 SBV_End_Immediate ..... | 37 | +| 8.3.10 Transparent processable data services ..... | 37 | +| 8.3.10.1 SBV_TPD_Begin ..... | 37 | +| 8.3.10.2 SBV_TPD_End ..... | 38 | +| 8.3.11 SBV_DFK ..... | 38 | +| 8.3.12 SBV_Remote_Echo ..... | 38 | +| 8.3.13 SBV_Escape ..... | 38 | + +| | Page | +|-----------------------------------------------------------------------------|-------------| +| 9 Coding ..... | 39 | +| 9.1 Coding of the Telematic Command PDUs ..... | 39 | +| 9.2 Coding structures ..... | 40 | +| 9.2.1 Basic coding structure ..... | 41 | +| 9.2.2 Extended coding structure ..... | 42 | +| 9.2.3 Coding of data types ..... | 42 | +| 9.2.3.1 Integers ..... | 42 | +| 9.2.3.2 Strings ..... | 42 | +| 9.2.3.3 Voids ..... | 42 | +| 9.2.3.4 Octet sequences ..... | 42 | +| 9.3 Coding of parameters ..... | 43 | +| 9.3.1 Coding of user data fields using the coding structures ..... | 43 | +| 9.3.2 Coding of user data fields as defined in other documents ..... | 45 | +| 9.3.3 Service specific coding ..... | 45 | +| 9.3.3.1 Coding of the Error_Code parameter ..... | 45 | +| 9.3.3.2 Coding of the DDU_Fall-Back_Mode parameter ..... | 47 | +| 9.3.3.3 Coding of the Function_Keys parameter ..... | 47 | +| 10 Use of CCITT Recommendation X.3 parameters ..... | 50 | +| 10.1 Selectable functions provided by Syntax-based Videotex Terminals ..... | 50 | +| 10.2 List of X.3 parameters ..... | 51 | +| 11 Bearer Independent Service (BIS) for Syntax-based Videotex ..... | 51 | +| 11.1 Introduction ..... | 51 | +| 11.2 Scope and field of application ..... | 52 | +| 11.3 General operation of the BIS ..... | 53 | +| 11.3.1 Out-Band Procedures for Environment-dependent operation ..... | 53 | +| 11.3.2 Translation of primitives and parameters of In-Band Procedures ..... | 54 | +| 11.4 Service primitives and parameters ..... | 55 | +| 11.4.1 NC establishment primitives and parameters ..... | 55 | +| 11.4.1.1 Association of primitives and parameters ..... | 55 | +| 11.4.1.2 Parameter definitions ..... | 55 | +| 11.4.2 NC release primitives and parameters ..... | 56 | +| 11.4.2.1 Association of primitives and parameters ..... | 56 | +| 11.4.2.2 Parameter definitions ..... | 57 | +| 11.4.3 Unqualified data transfer primitives and parameters ..... | 57 | +| 11.4.3.1 Association of primitives and parameters ..... | 57 | +| 11.4.3.2 Parameter definitions ..... | 58 | +| 11.4.4 Qualified data transfer primitives and parameters ..... | 58 | +| 11.4.4.1 Association of primitives and parameters ..... | 58 | +| 11.4.4.2 Parameter definitions ..... | 58 | +| 11.4.5 Interrupt data transfer primitives and parameters ..... | 58 | +| 11.4.5.1 Association of primitives and parameters ..... | 58 | +| 11.4.5.2 Parameter definitions ..... | 58 | +| 11.4.6 Reset primitives and parameters ..... | 59 | +| 11.4.6.1 Association of primitives and parameters ..... | 59 | +| 11.4.6.2 Parameter definitions ..... | 59 | +| 11.4.7 Relation of primitives at the two NC endpoints ..... | 59 | +| 11.4.8 Sequence of primitives at one NC endpoint ..... | 59 | +| 11.5 Elements of the X.25/PLP used to support the BIS ..... | 62 | +| 11.5.1 Types of virtual circuits ..... | 62 | +| 11.5.2 Packets and fields of the X.25/PLP used to support the BIS ..... | 62 | +| 11.5.3 Facilities of the X.25/PLP used to support the BIS ..... | 63 | + +| | Page | +|------------------------------------------------------------------------------|-------------| +| 11.6 Network connection establishment phase ..... | 63 | +| 11.6.1 Primitive/parameter and packet/field relationships ..... | 63 | +| 11.6.2 Procedures ..... | 64 | +| 11.6.2.1 General Function ..... | 64 | +| 11.6.2.2 Primitive/packet mapping ..... | 64 | +| 11.6.2.3 Addresses ..... | 64 | +| 11.6.2.4 User data ..... | 64 | +| 11.7 Network connection release phase ..... | 64 | +| 11.7.1 Primitive/parameter and packet/field relationships ..... | 64 | +| 11.7.2 Procedures ..... | 65 | +| 11.7.2.1 General Function ..... | 65 | +| 11.7.2.2 Primitive/packet mapping ..... | 65 | +| 11.7.2.3 Originator and Reason ..... | 66 | +| 11.7.2.4 Addresses ..... | 66 | +| 11.7.2.5 User data ..... | 66 | +| 11.8 Data transfer phase – (Unqualified) data transfer service ..... | 67 | +| 11.8.1 Primitive/parameter and packet/field relationships ..... | 67 | +| 11.8.2 Procedures ..... | 67 | +| 11.8.2.1 Primitive/packet mapping ..... | 67 | +| 11.8.2.2 User data ..... | 67 | +| 11.9 Data transfer phase – Qualified data transfer service (Q-bit = 1) ..... | 68 | +| 11.9.1 Primitive/parameter and packet/field relationships ..... | 68 | +| 11.9.2 Procedures ..... | 68 | +| 11.9.2.1 Primitive/packet mapping ..... | 68 | +| 11.9.2.2 User data ..... | 68 | +| 11.10 Data transfer phase – Reset service ..... | 68 | +| 11.10.1 Primitive/parameter and packet/field relationships ..... | 68 | +| 11.10.2 Procedures ..... | 69 | +| 11.10.2.1 General Function ..... | 69 | +| 11.10.2.2 Primitive/packet mapping ..... | 69 | +| 11.10.2.3 Originator and Reason ..... | 70 | +| 11.11 Data Transfer-Phase – Interrupt transfer service ..... | 70 | +| 11.11.1 Primitive/parameter and packet/field relationships ..... | 70 | +| 11.11.2 Procedures ..... | 70 | +| 11.11.2.1 Primitive/packet mapping ..... | 70 | +| 11.11.2.2 User data ..... | 71 | +| Annex A – Examples of configurations ..... | 71 | +| A.1 Symbols ..... | 71 | +| A.2 Access to PSTN/PSPDN systems using a terminal adaptor ..... | 71 | +| A.2.1 Analogue terminal adaptors ..... | 71 | +| A.2.2 Rate adapting terminal adaptors ..... | 72 | +| A.3 Connection to a VS via ISDN ..... | 72 | +| A.4 Access to a VS via an ISDN/PSPDN ..... | 73 | +| A.5 Access to a VS via an IVAP ..... | 73 | +| A.5.1 Service selection after a dialogue with the IVAP ..... | 74 | +| A.5.2 Service selection using a VS identification ..... | 74 | +| A.5.2.1 VS identified by a network address ..... | 74 | +| A.5.2.2 VS identified by a name ..... | 75 | +| A.5.3 Service selection using ISDN supplementary services ..... | 75 | +| A.5.4 Distributed Videotex Application ..... | 76 | +| A.5.4.1 Usage of a single VC between IVT and IVAP ..... | 76 | +| A.5.4.2 Establishment of the second VC by the IVT ..... | 77 | +| A.5.4.3 Establishment of the second VC by the IVAP ..... | 77 | +| A.6 Host to terminal call establishment ..... | 77 | +| A.7 Terminal to terminal communication ..... | 77 | + +| | Page | +|----------------------------------------------------------------|-------------| +| Annex B – Usage of supplementary services ..... | 79 | +| B.1    User-to-User Signalling (UUS) ..... | 79 | +| B.2    Supplementary services for addressing..... | 79 | +| B.2.1    Multiple Subscriber Number (MSN) ..... | 79 | +| B.2.2    Direct-Dialling-In (DDI) ..... | 79 | +| B.2.3    Subaddressing (SUB) ..... | 79 | +| B.2.4    Call Deflection (CD) ..... | 79 | +| B.3    Supplementary services for identification ..... | 80 | +| B.3.1    Calling Line Identification Presentation (CLIP) ..... | 80 | +| B.3.2    Calling Line Identification Restriction (CLIR) ..... | 80 | +| Annex C – Terminal Function basic state..... | 80 | +| C.1    X.3 parameter default values ..... | 80 | +| C.2    SBV_DFK default list..... | 81 | +| C.3    SBV_TPD default state..... | 81 | +| C.4    SBV_Escape default state ..... | 81 | +| Annex D – The SBV_Escape service..... | 81 | +| D.1    Service description ..... | 81 | +| D.1.1    Bulk Update ..... | 81 | +| D.2    Procedures ..... | 81 | +| D.2.1    Bulk Update ..... | 81 | +| D.3    Coding ..... | 82 | +| Annex E – Extended data forwarding signals ..... | 82 | +| Annex F – BIS constraints on ISO 8208 PICS..... | 83 | +| F.1    Introduction ..... | 83 | +| F.2    Tables structure..... | 83 | +| F.3    Constraints Tables ..... | 83 | +| F.3.1    Virtual circuit types ..... | 83 | +| F.3.2    Call setup ..... | 84 | +| F.3.3    Call clearing ..... | 84 | +| F.3.4    Resetting of logical channels ..... | 85 | +| F.3.5    Normal data transfer and flow control ..... | 85 | + +## SUMMARY + +This Recommendation specifies both: + +- the end-to-end Application Layer protocol for the Syntax-based Videotex service; and +- the underlying Bearer Independent Service. + +This Recommendation is applicable to all devices supporting the Bearer Independent Service on the upper side of the Network Layer and is therefore network independent. + +New or enhanced additional features can be offered compared with the traditional Videotex Services, e.g.: + +- direct selection of Videotex applications; +- multi-communication to several hosts or applications; +- multimedia communication (text, geometric, photographic, audio); +- distributed Videotex applications; +- use of supplementary services; +- handling of calls in both directions (outgoing, incoming). + +## SYNTAX-BASED VIDEOTEX APPLICATION LAYER PROTOCOL + +(Geneva, 1994) + +### 1 Scope + +This Recommendation specifies both the end-to-end Application Layer protocol for the Syntax-based Videotex Service and the underlying Bearer Independent Service (BIS). + +NOTE 1 – This Recommendation does not specify any service aspects of a Syntax-based Videotex Service. + +This Recommendation is applicable to all devices supporting the Bearer Independent Service on the upper side of the Network Layer (see clause 11). In the context of this Recommendation, a device is either a Videotex Terminal, a Videotex Service Centre, a Videotex Access Point or a Videotex Host (see 3.1). + +NOTE 2 – Depending on the communication type in use (e.g. ISDN DTE/DTE, ISDN DTE/DCE or PSTN), a separate Recommendation is assumed to be applicable for the respective lower layer protocols. + +### 2 Normative references + +The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision: all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of currently valid ITU-T Recommendations is regularly published. + +- [1] CCITT Recommendation F.300 (1988), *Videotex Service*. +- [2] CCITT Recommendation T.51 (1988), *Coded character sets for telematic services*. +- [3] CCITT Recommendation X.3, *Packet assembly/disassembly facility (PAD) in a public data network*. +- [4] CCITT Recommendation X.25 (1980), *Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit*. +- [5] CCITT Recommendation X.25 (1984 or later), *Interface between data terminal equipment (DTE) and data circuit-terminating equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit*. +- [6] CCITT Recommendation X.29, *Procedures for the exchange of control information and user data between a packet assembly/disassembly (PAD) facility and a packet mode DTE or another PAD*. +- [7] CCITT Recommendation X.121 (1992), *International numbering plan for public data networks*. +- [8] CCITT Recommendation T.101, *International interworking for Videotex services*. +- [9] CCITT Recommendation T.102, *Syntax-based Videotex End-to-End protocols for circuit mode ISDN*. +- [10] CCITT Recommendation T.103, *Syntax-based Videotex End-to-End protocols for packet mode ISDN*. +- [11] CCITT Recommendation T.104, *Packet mode access for syntax-based Videotex via PSTN*. +- [12] CCITT Recommendation T.106, *Framework of Videotex terminal protocols*. + +- [13] CCITT Recommendation X.200, *Reference model of Open Systems Interconnection for CCITT applications.* +- [14] ISO 7498, *Information processing systems – Open Systems Interconnection – Basic Reference Model.* +- [15] ISO/IEC 8208 (1990), *Information technology – Data Communications – X.25 Packet Layer Protocol for Data Terminal Equipment.* +- [16] ISO/IEC 8208:1990/Am.3 (1991), *Information technology – Data Communications – X.25 Packet Layer Protocol for Data Terminal Equipment – Amendment 3: Conformance Requirements.* +- [17] ISO/TR 8509, *Information processing systems – Open Systems Interconnection – Service conventions.* + +## 3 Definitions and abbreviations + +### 3.1 Definitions + +For the purposes of this Recommendation, the following definitions apply: + +**access function:** The functional entity which gives access to the Videotex Service. This entity is an integral part of the Videotex Service. + +**access network:** The network which provides the link between the Terminal Function and the Access Function. + +**application layer:** See OSI Reference Model CCITT Rec. X.200 [13] | ISO 7498 [14]. + +**audio data:** Generic term for data which can be made audible (e.g. wave form encoded, phonemically encoded). + +**bearer independent service access point:** Point in an end system where the user of the Bearer Independent Service accesses the service. + +**called BIS user:** A BIS user with whom a calling BIS user wishes to establish a NC. + +**calling BIS user:** A BIS user that initiates a NC establishment request. + +**confirm:** See Service Conventions Standard ISO/TR 8509 [17]. + +**data circuit-terminating equipment:** See ISO/IEC 8208 [15] and CCITT Recommendation X.25 [5]. + +**data terminal equipment:** See ISO/IEC 8208 [15] and CCITT Recommendation X.25 [5]. + +**distributed videotex application:** A Videotex Application which makes use of more than one Videotex Host. + +**host access network:** The network which provides the link between the Access Function and the Host Function(s). It is an integral part of the Videotex Service and may be void. + +**host function:** The abstraction of the Videotex Applications available in a particular Videotex Service. + +**in-band:** All communication aspects related to CCITT Recommendation X.29 [6] (including Telematic Commands) based procedures. + +**indication:** See Service Conventions Standard ISO/TR 8509 [17]. + +**logical channel:** See ISO/IEC 8208 [15] and CCITT Recommendation X.25 [5]. + +**multimedia communication:** Term used to indicate that both pictorial and audio data are exchanged. + +**network connection:** See OSI Reference Model CCITT Recommendation X.200 [13] | ISO 7498 [14]. + +**network layer:** See OSI Reference Model CCITT Recommendation X.200 [13] | ISO 7498 [14]. + +**network service:** See OSI Reference Model CCITT Recommendation X.200 [13] | ISO 7498 [14]. + +**out-band:** All communication aspects related to procedures not being based on CCITT Recommendation X.29 [6] (including Telematic Commands), e.g. in case of an ISDN the use of the D-channel for B-channel establishment. + +**packet layer:** See ISO/IEC 8208 [15] and CCITT Recommendation X.25 [5]. + +**pictorial data:** Generic term for data which can be displayed (e.g. alphamosaic, geometric, photographic). + +**primitive:** See Service Conventions Standard ISO/TR 8509 [17]. + +**request:** See Service Conventions Standard ISO/TR 8509 [17]. + +**response:** See Service Conventions Standard ISO/TR 8509 [17]. + +**telematic command:** In the scope of this Recommendation, a Telematic Command is a specific service element which is carried in a complete packet sequence of X.25 Packet Layer Protocol DATA packets with the Q-bit set to 1. The first octet in the User Data field of the first packet of the complete packet sequence carries a value which is reserved for videotex [see CCITT Recommendation X.29 (1992), “Telematic service message, videotex”]. + +**terminal function:** The abstraction of a functional entity which acts as a Videotex Terminal. + +**videotex access point:** See CCITT Recommendation F.300 [1]. + +**videotex application:** See CCITT Recommendation F.300 [1]. + +**videotex external host:** See CCITT Recommendation F.300 [1]. + +**videotex host:** This term describes a computer which offers one or more applications and/or facilities. It can be represented through a Videotex Host Computer, an External Videotex Host or a Videotex Service Centre. + +**videotex host computer:** See CCITT Recommendation F.300 [1]. + +**videotex service:** See CCITT Recommendation F.300 [1]. + +**videotex service centre:** See CCITT Recommendation F.300 [1]. + +NOTE – According to CCITT Recommendation F.300, a Videotex Service Centre provides host and/or access functions, i.e. it may also act as a Videotex Access Point. + +**videotex terminal:** See CCITT Recommendation F.300 [1]. + +**virtual call:** See ISO/IEC 8208 [15] and CCITT Recommendation X.25 [5]. + +**virtual circuit:** See ISO/IEC 8208 [15] and CCITT Recommendation X.25 [5]. + +## 3.2 Abbreviations + +For the purposes of this Recommendation, the following abbreviations apply: + +| | | +|-------|--------------------------------------------------------------| +| AP | Access Point | +| AU | Access Unit | +| BIS | Bearer Independent Service | +| CCITT | International Telegraph and Telephone Consultative Committee | +| CD | Call Deflection | +| CLIP | Calling Line Identification Presentation | +| CLIR | Calling Line Identification Restriction | +| DCE | Data Circuit-terminating Equipment | +| DDI | Direct-Dialling-In | +| DDU | Dialogue DU | + +| | | +|-------|--------------------------------------------------------------------------------------------------------------| +| DFK | Definable Function Key | +| DS | Data Syntax | +| DTE | Data Terminal Equipment | +| DU | Data Unit | +| DXE | Either a DTE or a DCE | +| HAN | Host Access Network | +| IB | In-Band | +| ISDN | Integrated Services Digital Network | +| ISO | International Organization for Standardization | +| ITU-T | International Telecommunication Union – Telecommunication Standardization Sector (formerly known as “CCITT”) | +| IVAP | ISDN syntax-based VAP | +| IVT | ISDN syntax-based VT | +| LC | Logical Channel | +| LSB | Least Significant Bit | +| M-bit | More Data bit | +| MBS | M-bit Sequence | +| MSB | Most Significant Bit | +| MSN | Multiple Subscriber Number | +| NC | Network Connection | +| NL | Network Layer | +| OB | Out-Band | +| OSI | Open Systems Interconnection | +| PDN | Public Data Network | +| PDU | Protocol DU | +| PH | Packet Handler | +| PLP | Packet Level Protocol | +| PSPDN | Packet Switched Public Data Network | +| PSTN | Public Switched Telephone Network | +| Q-bit | Qualifier bit | +| SBV | Syntax-Based Videotex | +| SUB | Subaddressing | +| TC | Telematic Command | +| TCH | TC Header | +| TCM | TC Message | +| TDU | Telesoftware DU | +| TFI | Terminal Facility Identifier | +| TPD | Transparent Processable Data | +| UUI | User-to-User Information | +| UUS | User-to-User Signalling | +| VAP | Videotex AP | +| VC | Virtual Call | +| VH | Videotex Host | +| VPDE | Videotex Presentation Data Element | +| VS | Videotex Service | +| VT | Videotex Terminal | + +## 4 Overview + +The main feature of a Syntax-based Videotex Terminal (VT) is the capability to access those Videotex Services which are defined for and used in a Public Switched Telephone Network (PSTN) or Packet Switched Public Data Network (PSPDN) environment using the X.25 Packet Layer Protocol (X.25/PLP) on an arbitrary access network. + +More advanced Videotex Services may make use of additional features which are presented in the following subclauses. + +### 4.1 Direct selection of Videotex Applications + +The protocol allows the Videotex Terminal to shortcut the dialogue and welcome phase of the Videotex Service and to be connected with a given Videotex Application identified by a network address or a mnemonic. + +### 4.2 Multicommunication + +Multicommunication allows a terminal to establish several independent communication channels to one or several independent Videotex Hosts or Videotex Applications. + +The protocol supports multicommunication using several Network connections. + +#### NOTES + +- 1 In the case of an ISDN, several Network connections may be provided using one B-channel, only. +- 2 The handling of several independent communication channels may appear in any configuration [see Annex A (informative)]. + +**EXAMPLE:** Assume that “ETSI” and “ITU-T” are two Videotex Applications offering the possibility to Videotex users to read texts of telecommunication Recommendations. In order to compare the text of a given Recommendation with an equivalent standard, the terminal should establish a network connection with each of the two applications. The information from the two applications shall be simultaneously displayed on the terminal using some windowing capability. + +### 4.3 Multimedia communication + +Multimedia information may contain pictorial data (i.e. alphamosaic, geometric, and photographic display elements) and audio data. The audio data may be transmitted either in parallel or in serial with the pictorial data. + +When the audio data is transmitted in serial with the pictorial data, a single Network connection may be used to carry both. + +When the audio data has to be sent in parallel with the pictorial data, a second Network connection dedicated to the transmission of audio data shall be setup. + +The protocol supports multimedia communication using several Network connections, providing for the simultaneous reproduction of both pictorial and audio information, in addition to a serial transmission already covered by the data syntax. + +#### NOTES + +- 1 In the case of an ISDN, several Network connections may be provided using one B-channel, only. +- 2 The handling of several additional communication channels may appear in any configuration [see Annex A (informative)]. + +### 4.4 Distributed Videotex Application + +It is recognized that, to accomplish some specific application, the application may be decomposed into several sub-applications which may be implemented on more than one host. A communication channel from the terminal to each of the sub-applications may exist. The incoming datastreams are combined in the terminal to deliver the desired service to the user. + +The protocol supports distributed Videotex Applications using several Network connections. + +NOTE – In the case of an ISDN, several Network connections may be provided using one B-channel, only. + +EXAMPLE: Assume an application which serves PSTN terminals and ISDN terminals at the same time. The PSTN application uses only alphamosaic information, while the ISDN application additionally offers photographic pictures. The “alphamosaic-host” is used for the dialogue with both PSTN and ISDN terminals. When a specific picture has to be displayed, on request of the “dialogue-host” a second VC is established between the ISDN terminal and the “picture-host”. + +## 4.5 Supplementary services + +In the case of an ISDN, the protocol allows for a use of several ISDN supplementary services [Multiple Subscriber Number (MSN), Subaddressing (SUB), User-to-User Signalling 1 (UUS 1), Call Deflection (CD), Calling Line Identification Presentation (CLIP) and Calling Line Identification Restriction (CLIR)], mainly to support ISDN-specific Videotex Service selection mechanisms. For details on these supplementary services, refer to Annex B (informative). + +NOTE – The use of supplementary services on networks other than an ISDN is for further study. + +## 4.6 Handling of incoming calls + +The protocol permits a Syntax-based Videotex Terminal to be called by another terminal or a Videotex Service. + +In the case of a called Syntax-based Videotex Terminal, the handling of supplementary services is not within the scope of this Recommendation. + +# 5 Configurations + +Various configurations and topologies may be used, examples of which are given in Annex A (informative). It shall be the responsibility of the Videotex Service providers to opt for the appropriate configuration(s) in the definition of the Syntax-based Videotex Service. + +## 6 General model + +In order to describe all configurations, the following reference models are used: + +- a communication model; +- a terminal model. + +The communication model describes the relationships between the functional entities involved in the communication. It models the communication between a user and a Videotex Service in terms of terminal functions, access network functions and service functions. + +The terminal model defines, in an abstract way, the terminal aspects which are relevant for the protocol. + +### 6.1 Communication model + +In describing the communication model, the following entities can be identified: + +- a User; +- a Terminal Function; +- an Access Network; +- an Access Function; +- a Host Access Network; +- a Host Function. + +In all Videotex configurations, the **User** employs a terminal to communicate with a Videotex Service. The abstraction of the terminal is named **Terminal Function**. + +The **Access Network** provides the link between the Terminal Function and the Videotex Service. It may consist of one or several networks of different types. The Bearer Independent Service (BIS) provides the interface to the access network (see clause 11). + +NOTE – The definition of the relation between the BIS and a specific access network is not in the scope of this Recommendation. + +The **Access Function** is the functional entity which gives access to the Videotex systems. It is an integral part of the Videotex Service. + +The **Host Access Network**, which is an optional functional entity, is the abstraction of the function, which connects the Access Function to one or more Host Functions. Depending on the actual topology used in a specific service, it may be void. + +The **Host Function** is the abstraction of the collection of Videotex Applications. + +The interfaces and protocols defined between the functional entities are: + +- (1) User interface +- (2) Terminal-Access Network interface +- (3) Access Function-Access Network interface +- (4) Access Function-Host Access Network interface +- (5) Host Function-Host Access Network interface +- (6) Terminal-Access Function protocol +- (7) Host Access protocol + +Figure 1 shows the relationships between the entities. + +Of these interfaces and protocols, only protocol (6) is within the scope of this Recommendation, interfaces (2) and (3) are provided by the BIS. + +![Figure 1/T.105: Communication Model diagram showing the relationships between User, Terminal Function, Access Network, Access Function, Host Access Network, and Host Function.](a7c51c18111139f9aca2805114108565_img.jpg) + +The diagram illustrates the communication model between various functional entities. It consists of the following components and connections: + +- User**: A box at the top left connected to the **Terminal Function** by a solid line labeled (1) with a double-dash symbol. +- Terminal Function**: A box below the User, connected to the **Access Network** by a solid line labeled (2) with a double-dash symbol. +- Access Network**: A central box connected to the **Access Function** by a solid line labeled (3) with a double-dash symbol. +- Access Function**: A box below the Access Network, connected to the **Host Access Network** by a solid line labeled (4) with a double-dash symbol. +- Host Access Network**: A box above the Access Function, connected to the **Host Function** by a solid line labeled (5) with a double-dash symbol. +- Host Function**: A box at the top right, connected to the **Access Function** by a solid line labeled (7). + +Additionally, a dashed line connects the **Host Function** to the **Access Function**, and another dashed line connects the **Host Function** to the **Host Access Network**. A long solid line labeled (6) connects the **Terminal Function** directly to the **Access Function**. + +T0815140-94/d01 + +Figure 1/T.105: Communication Model diagram showing the relationships between User, Terminal Function, Access Network, Access Function, Host Access Network, and Host Function. + +FIGURE 1/T.105 +Communication Model + +## 6.2 Terminal model + +The terminal model is the reference model which is used throughout the document. This model describes the relationships between functions of a Syntax-based Videotex Terminal. + +The Application Layer is decomposed into the following components: + +- communication channel manager; +- Layer 7 protocol machine; +- input buffer; +- output buffer; +- echo handler; +- forwarding condition handler; +- processable data unit; +- escape function units. + +The protocol machine handling Layers 1-3 of the protocol and the co-ordination function are integral parts of the BIS entity and do not require further refinement in the terminal model. + +NOTE 1 – Depending on the access network and the communication mode, the co-ordination function may also be empty. + +Figure 2 introduces these functions and their relationship. + +![Figure 2: Functional entities of the terminal model. The diagram shows the internal structure of the SBV application (service) and its connection to the Bearer Independent Service (BIS).](cb4cfa42ce34febde7bdb882f3fc3094_img.jpg) + +The diagram illustrates the functional entities of the terminal model. It is divided into two main sections: the SBV application (service) and the Bearer Independent Service (BIS). + +**SBV application (service):** This section is enclosed in a large rectangle. Inside, a dotted rectangle contains several functional entities: User Input, Forwarding condition Handler, Input Buffer, Echo Handler, User Output, Output Buffer, Layer 7 Protocol Machine, Escape Functions (represented by a stack of three boxes), and Processable Data Unit. The connections are as follows: User Input connects to the Input Buffer, which connects to the Forwarding condition Handler. The Forwarding condition Handler connects to the Layer 7 Protocol Machine. The Layer 7 Protocol Machine connects to the Echo Handler, which connects to the Output Buffer. The Output Buffer connects to User Output. The Layer 7 Protocol Machine also connects to the Processable Data Unit. The Escape Functions are connected to the Output Buffer and the Processable Data Unit. + +**Bearer Independent Service (BIS):** This section is enclosed in a separate rectangle. It contains two functional entities: Coordination Function and Layer 1-3 Protocol Machine. The Coordination Function connects to the Layer 1-3 Protocol Machine. The Layer 1-3 Protocol Machine connects to the Commun. Channel Manager, which is located between the SBV application and the BIS. The Commun. Channel Manager connects to the Layer 1-3 Protocol Machine. The Layer 1-3 Protocol Machine connects to the S/T (Service/Transfer) interface. + +NOTE – For every communication channel, one separate independent instance of each of the functional entities inside the dotted rectangle exists. + +T0815150-94/d02 + +Figure 2: Functional entities of the terminal model. The diagram shows the internal structure of the SBV application (service) and its connection to the Bearer Independent Service (BIS). + +FIGURE 2/T.105 + +Functional entities of the terminal model + +In the context of this Recommendation, a **communication channel** is equivalent to an established Network connection. + +The **communication channel manager** supervises the handling of related communication channels. The protocol allows for the definition of a hierarchical relationship between communication channels. An application can request the establishment of further dependent communication channels via an already established communication channel. The requesting communication channel shall be named a “Master”-channel and the requested communication channels shall be named “Slave”-channels. + +NOTE 2 – The handling of more than one communication channel is optional. Therefore, the communication channel manager may also be empty. + +This relationship is maintained during the lifetime of a communication channel implying that existing “Slave”-channels have to be closed implicitly when the “Master”-channel is closed. The communication channel manager takes care of this implicit closure and keeps track of related communication channels. + +NOTE 3 – A communication channel may be a “Slave”-channel and a “Master”-channel at the same moment, provided: + +- 1) it is related to a “Master”-channel; +- 2) there is at least one “Slave”-channel related to this channel. + +For each established communication channel, one separate independent (virtual) instance of the following functional entities exists (regardless of whether it is an independent or a linked communication channel). + +The **Layer 7 protocol machine** supports the procedures as defined in the Application Layer protocol (see clause 8). It conveys information to the output buffer (display data), the echo handler (parameter settings, related to echoing), the forwarding condition handler (parameter settings, related to forwarding and function key information), the communication channel manager (related communication channels) or the processable data or escape modules. + +The **input buffer** receives the user input, which subsequently is forwarded to the protocol machine in order to be transmitted to the Access Function, and which may be used in parallel by the echo handler. A terminal may locally edit this buffer. The origin of data entered in the input buffer need not be defined, having no relevance for the description of the protocol of this Recommendation. + +NOTE 4 – The specification of local editing is outside the scope of this Recommendation. + +The **output buffer** receives display data from both the Layer 7 protocol machine and the echo handler. The processing of display data is not described in the model having no relevance for the description of the protocol of this Recommendation. + +The **echo handler** controls the echoplex procedures. With regard to echoing, the state diagram in Figure 3 shall apply. + +When echoing is enabled, the initial terminal state shall be ECHO\_ACTIVE. The initial state of echoing is defined in Annex C (normative). + +In the state ECHO\_ACTIVE, all user input shall be echoed immediately. Echoing shall be performed on a character basis in the sense of Recommendation T.101 [8]. + +As long as no data have been received from the Access Function, the terminal remains in the state ECHO\_ACTIVE. + +When the terminal is in the state ECHO\_ACTIVE and data are received from the Access Function, one of the following shall apply: + +- if an end-of-frame condition has been set (CCITT Recommendation X.3 [3] extended parameter reference 24 is not implemented or set to a non-zero value, see clause 10), the terminal shall enter the state ECHO\_SUSPENDED; +- if no end-of-frame condition has been set (parameter reference 24 is set to 0), the terminal shall remain in the state ECHO\_ACTIVE. + +When the terminal is in the state ECHO\_SUSPENDED, data received from the Access Function shall be processed (e.g. displayed) and the echoing of user input shall be suspended until an end-of-frame has been detected. + +![ECHO handler state diagram showing transitions between ECHO_SUSPENDED and ECHO_ACTIVE states.](76b0cd79baaedd942af4dc42f2e764b8_img.jpg) + +``` + + graph LR + ECHO_SUSPENDED((ECHO +SUSPENDED)) + ECHO_ACTIVE((ECHO +ACTIVE)) + SuspendEcho[Suspend +Echo] + ProcessUserInputActive[Process +user +input] + ProcessSuspendedUserInput[Process +suspended +user input] + DataFromAccessFunctionActive[Data from Access +Function AND +parameter reference 24 = 0] + DataFromAccessFunctionSuspended[Data from +Access Function] + EndOfFrameEncountered[End-of-frame +condition +encountered] + UserInputActive[User input] + UserInputSuspended[User input] + ParamRef2[Parameter reference 2: +value greater than 0] + + ECHO_SUSPENDED -- "Data from Access Function" --> ECHO_SUSPENDED + ECHO_SUSPENDED -- "User input" --> SuspendEcho + SuspendEcho --> ECHO_SUSPENDED + ECHO_SUSPENDED -- "End-of-frame condition encountered" --> ProcessSuspendedUserInput + ProcessSuspendedUserInput --> ECHO_ACTIVE + ECHO_ACTIVE -- "Data from Access Function AND parameter reference 24 = 0" --> ECHO_ACTIVE + ECHO_ACTIVE -- "User input" --> ProcessUserInputActive + ProcessUserInputActive --> ECHO_ACTIVE + ECHO_ACTIVE -- "User input" --> ECHO_SUSPENDED + ECHO_ACTIVE -- "Parameter reference 2: value greater than 0" --> ECHO_ACTIVE + ECHO_ACTIVE -- "Data from Access Function and end-of-frame condition defined" --> ECHO_SUSPENDED + +``` + +The diagram illustrates the state transitions for the ECHO handler. It features two main states: ECHO\_SUSPENDED and ECHO\_ACTIVE. Transitions are triggered by various inputs and conditions, leading to actions like suspending or processing user input, or returning to a specific state. A reference to T0815160-94/d03 is present near the ECHO\_ACTIVE state. + +ECHO handler state diagram showing transitions between ECHO\_SUSPENDED and ECHO\_ACTIVE states. + +NOTE – An end-of-frame condition is defined if either CCITT Recommendation X.3 [3] extended parameter reference 24 is not implemented or if parameter reference 24 has been set to a non-zero value. + +FIGURE 3/T.105 +Echo handler state diagram + +When an end-of-frame has been detected in the ECHO\_SUSPENDED state, suspended user input shall be processed (e.g. displayed) immediately prior to any other action and the terminal shall return to the ECHO\_ACTIVE state. + +The possible end-of-frame conditions are: + +- the receipt of a complete packet sequence shall be an end-of-frame condition, if CCITT Recommendation X.3 [3] extended parameter reference 24 is not implemented; +- end-of-frame conditions as defined by parameter reference 24; +- the receipt of an SBV PDU different from the SBV\_VTX\_Data PDU is considered to be an implicit end-of-frame condition. + +Certain possibly defined end-of-frame conditions can be checked for by inspecting the contents of the output buffer. + +The **forwarding condition handler** manages the forwarding conditions and upon user input forwards data to the Layer 7 protocol machine. It also takes care of the currently defined user input field length (see clause 10). + +NOTE 5 – The handling of the input field is a local matter. + +The forwarding conditions can be divided into the following groups in a hierarchical order (i.e. lower numbered conditions have precedence): + +- 1) X.29 PAD messages (mandatory); +- 2) X.3 idle timer expiration (mandatory); + +- 3) X.3 standard forwarding conditions (mandatory); +- 4) X.3 extended forwarding conditions (optional); +- 5) definable forwarding conditions (optional). + +NOTE 6 – It is a local matter to decide at which point in time the Application Layer data are assembled into X.25 packets. Nevertheless, it is expected that these packets are forwarded whenever a packet is full. + +CCITT Recommendation X.29 [6], 2.1, specifies the receipt of a PAD message as a forwarding condition. PAD messages are used to set and read parameters. + +If the idle timer is set to values $> 0$ , the contents of the input buffer shall be forwarded if the input buffer has remained unchanged for the period of time as defined by the current value of the idle timer parameter. + +CCITT Recommendation X.3 [3] standard forwarding conditions define single octets which trigger forwarding when encountered in the input buffer. The default X.3 forwarding conditions are given in Annex C (normative). + +CCITT Recommendation X.3 [3] extended forwarding conditions (see clause 10) define fixed multi-octet sequences, which are in use in Videotex systems, accessed over the PSTN or the PSPDN [see Annex E (informative)]. + +Definable function keys can be set by the service to define arbitrary forwarding conditions. The support of definable function keys is optional. These conditions are additional to the CCITT Recommendation X.3 [3] forwarding conditions. In cases of an ambiguity between these different sets of forwarding conditions, the CCITT Recommendation X.3 [3] conditions shall have the higher priority. + +A terminal supporting definable function keys shall be capable of handling a minimum of 8 function keys with identifications 1 to 8. These function keys may be linked to forwarding conditions. An optional user visible name element may be used to distinguish the functions for the user. The function key definitions may be changed by sending a new definition for some specific key, or deleted by either overwriting them with an empty definition (zero length code sequence) or by resetting all definable function keys. + +EXAMPLE: To adapt an ISDN syntax based videotex terminal to a system using function keys INDEX, HELP, DELETE, CORRECT, PREVIOUS, NEXT, REPEAT and SEND in a Videotex Service X, forwarding conditions may be downloaded with key 1 being INDEX, key 2 being HELP, etc. and corresponding codes (e.g. 1/3 x/y). To use this terminal in Videotex Service Y using the same function keys, but other code sequences (e.g. the code sequence for CORRECT shall be 0/8 instead of 1/3 4/7), forwarding conditions are downloaded according to the environment. + +A terminal supporting definable function keys may abstain from treating a character sequence as a forwarding condition, if it is entered directly into the input buffer, even though this character sequence is identical to an already defined forwarding condition code sequence linked to a function key. By definition, this rule applies only to definable forwarding conditions as these provide a way to link forwarding conditions to function keys. CCITT Recommendation X.3 [3] forwarding conditions are not subject to this rule. The default state of the list of function keys is specified in Annex C (normative). + +NOTE 7 – This rule eases implementations, because otherwise terminals should be capable of interpreting long sequences of input characters. + +The **processable data unit** handles processable data as defined in CCITT Recommendation T.101 [8]. It may also be capable of handling processable data transparently without making use of the Dialogue Data Units (DDUs). The default regime to be used for conveying processable data is defined in Annex C (normative). + +The **escape functions** handle services which are not specified in this Recommendation. The default states of processes related to SBV\_Escape subservices are defined in Annex D (normative). + +## 6.3 Protocol pillar + +The protocol pillar to be used to convey the SBV protocol is as given in Figure 4. + +| | | +|---|--------------------------------| +| 7 | T.105
T.101 [8] data syntax | +| 6 | null (Note 1) | +| 5 | null (Note 2) | +| 4 | null (Note 2) | +| 3 | (Note 3) (Note 4) | +| 2 | (Note 3) | +| 1 | (Note 3) | + +Layer + +#### NOTES + +- 1 The main purpose of Layer 6, the conversion from the “abstract syntax” to the “transfer syntax” is not necessary, because in this case the abstract data syntax in Layer 7 is identical to the transfer data syntax. Also all other features of the Layer 6 are not used and therefore “null” is inserted for Layer 6. The abstract syntax in Layer 7 and the coding in Layer 6 correspond to the data syntaxes DS I, DS II and DS III in CCITT Recommendation T.101 [8]. +- 2 For the time being, it is not the intention to include Layers 4 and 5. +- 3 Not defined by this Recommendation. +- 4 The upper service interface of Layer 3 shall be in accordance with the BIS as defined in this Recommendation. + +FIGURE 4/T.105 +**Protocol pillar** + +The application layer protocol (SBV protocol) is defined in this Recommendation. + +The data syntax used for syntax-based Videotex is defined in Recommendation T.101 [8]. + +The lower layer (Layer 1 to Layer 3) protocols are out of the scope of this Recommendation. However, the upper service interface of Layer 3 shall be in accordance with the BIS as defined in clause 11. + +NOTE – Recommendation T.106 [12] gives an overview of how the SBV protocol can be conveyed using different types of networks. Lower layer Recommendations for this purpose are also shown in Recommendation T.106 [12]. + +## 7 Service definition + +### 7.1 Introduction + +The Syntax-based Videotex Application Layer incorporates some functionalities related to those Videotex Services originally defined for the PSTN/PSPDN environment, as well as functionalities related to the additional features as stated in clause 4. + +This clause describes, in an abstract way, the services offered by the Syntax-based Videotex Application Layer in terms of: + +- the primitive actions and events of the service; +- the parameter data associated with each primitive action and event. + +The services are divided into two classes: + +- Mandatory Kernel services (see Table 1); +- Optional services (see Table 2). + +TABLE 1/T.105 + +**Kernel services (mandatory)** + +| Kernel Service | C/NC | Initiated by TF/AF | Function | +|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------|--------------------|------------------------------------------------------------| +| SBV_Establish | C | TF | Connection establishment | +| SBV_Release | NC | Both | Connection release | +| SBV_Reset | C | AF | Reset to basic state | +| SBV_VTX_Data | NC | Both | Videotex data transfer | +| SBV_Set_Param | NC | AF | Set X.3 parameters | +| SBV_Read_Param | NC | AF | Read X.3 parameters | +| SBV_Set_Read_Param | NC | AF | Set and read X.3 parameters | +| SBV_Param_Indication | NC | TF | X.3 parameter indication | +| SBV_TFI | C | AF
(Note) | Exchange of Terminal Facility Identifier (TFI) information | +| SBV_TC_Error | NC | Both | Telematic Command Error Message | +|

C Confirmed service
NC Non-confirmed service
AF Access Function
TF Terminal Function

NOTE – The support of the SBV_TFI service element shall be mandatory for Syntax-based Videotex Terminals only. It shall be up to the Videotex Service to employ this terminal capability.

For an interim period the implementation of this service element is optional, as long as the TFI is implemented in the terminal and can be transferred in the SBV_VTX_Data service element.

| | | | + +For every service described below, parameters may be mandatory or optional. Mandatory parameters shall always be present within the primitives used to convey the service element and shall be coded as defined in clause 9. Optional parameters need not be present within the primitive used to convey the service element; if an optional parameter is present, it shall be coded according to clause 9; if it is not present, no information shall be associated to this event (i.e. no default value is defined for any parameter). + +The protocol is used between a Terminal Function and an Access Function and as such is not symmetrical, because some services shall be invoked by the Terminal Function or the Access Function only. + +The default role assignment shall be defined as follows: the **calling** side (i.e. the entity which issues an SBV\_Establish Request) shall act as the Terminal Function; the **called** side (i.e. the entity which receives an SBV\_Establish Indication) shall act as the Access Function. + +NOTE – This role assignment may be reversed upon indication by the caller, but only if the called side accepts (see 7.2.1). + +TABLE 2/T.105 + +**Optional services** + +| Telematic Command | C/NC | Initiated by
TF/AF | Function | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------|-----------------------|--------------------------------------------------------------| +| SBV_Channel_Open (Note 1) | C | AF | Invitation to establish an additional communication channel | +| SBV_Channel_Close (Note 1) | C | AF | Invitation to release an additional communication channel | +| SBV_Channel-Error (Note 1) | NC | TF | Additional communication channel error message | +| SBV_Begin_Application | C | TF | Direct selection of a Videotex Application | +| SBV_End_Application (Note 2) | NC | TF | Return to the Videotex Application selection phase | +| SBV_End_Immediate (Note 2) | NC | TF | Immediate return to the Videotex Application selection phase | +| SBV_TPD_Begin (Note 3) | C | Both | Begin of transparent processable data exchange regime | +| SBV_TPD_End (Note 3) | NC | Both | End of transparent processable data exchange regime | +| SBV_DFK | NC | AF | Definition of function keys | +| SBV_Remote_Echo | NC | TF | Invitation to set the remote echo ON or OFF | +| SBV_Escape | NC | Both | Services not standardized in this Recommendation | +|

C Confirmed service
NC Non-confirmed service
AF Access Function
TF Terminal Function

NOTES

1 If implemented, all three communication channel management services shall be supported.

2 If implemented at AF side, both services shall be supported, except terminals conforming to Recommendation T.105 as per COM VIII-R 47 (1992).

3 If implemented, both Transparent Processable Data (TPD) services shall be supported.

| | | | + +**7.2 Kernel services****7.2.1 SBV\_Establish** + +The SBV\_Establish service element shall be used to establish a communication. It may be initiated by the Terminal Function only. This service is confirmed, but in case a communication cannot be established this shall be indicated using the SBV\_Release service. + +A Syntax-based Videotex Terminal shall not be obliged to handle an incoming call. + +NOTE 1 – This service allows for a direct selection of a Videotex Application. This direct selection may also be accomplished using the SBV\_Begin\_Application service, once the communication establishment has been successful. + +NOTE 2 – This service may be used to establish several network connections. It is out of the scope for this Recommendation whether to open an additional bearer channel or to establish another network connection on the existing bearer channel. In case of an ISDN a bearer channel is equivalent to a B-channel. + +NOTE 3 – A Videotex Service calling an SBV Terminal acts, in terms of the communication model (see 6.1), as a Terminal Function, at least up to that point in time when both sides agree to reverse the role assignment. + +The primitives and parameters of the SBV\_Establish service are described in Table 3 below. + +TABLE 3/T.105 + +| Parameters | Request | Indication | Response | Confirm | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|--------------|----------|--------------| +| OB_Called_Address | Optional | Optional (=) | – | – | +| OB_Called_Subaddress | Optional | Optional (=) | – | – | +| OB_Application_Address | Optional | Optional (=) | – | – | +| OB_Application_Selection | Optional | Optional (=) | – | – | +| OB_Application_Data | Optional | Optional (=) | – | – | +| OB_User_Data | Optional | Optional (=) | – | – | +| IB_Called_Address | Optional | Optional (=) | – | – | +| IB_Application_Address | Optional | Optional (=) | – | – | +| IB_Application_Selection | Optional | Optional (=) | – | – | +| IB_Application_Data | Optional | Optional (=) | – | – | +| IB_User_Data | Optional | Optional (=) | – | – | +| Reference | Optional | Optional (=) | – | – | +| Reverse_Role_Assignment | Optional | Optional (=) | – | – | +| Result | – | – | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request or Response primitive.
NOTE – Depending on the network and/or access type it might be necessary to have one or several of these parameters present in a Request in order to establish a communication. However, this is out of the scope of this Recommendation. | | | | | + +#### Parameters: + +- **OB\_Called\_Address** – This parameter carries the Out-Band address of the Access Function to be reached. +- **OB\_Called\_Subaddress** – This parameter carries the Out-Band subaddress of the Access Function; it may only be present if the OB\_Called\_Address parameter is present. +- **OB\_Application\_Address** – This parameter carries complementary information about the Videotex Application to be reached; this may include a network address which is interpreted by the Access Function. +- **OB\_Application\_Selection** – This parameter carries complementary information (e.g. mnemonic) about the Videotex Application to be reached; this is interpreted by the Access Function. +- **OB\_Application\_Data** – This parameter carries data to be sent to the Videotex Application to be reached; it is passed transparently to the Host Function via the Access Function. +- **OB\_User\_Data** – This parameter carries user data not specified in this Recommendation which is interpreted by the Access Function. + +- **IB\_Called\_Address** – This parameter carries an In-Band address; it either represents an address of the Videotex Application to be reached in which case it is interpreted by the Access Function or it represents a network address used by the Access Network to identify the called side. +- **IB\_Application\_Address** – This parameter carries complementary information about the Videotex Application to be reached; this may include a network address; it is interpreted by the Access Function. +- **IB\_Application\_Selection** – This parameter carries complementary information (e.g. mnemonic) about the Videotex Application to be reached; it is interpreted by the Access Function. +- **IB\_Application\_Data** – This parameter carries data to be sent to the Videotex Application to be reached; it is passed transparently to the Host Function via the Access Function. +- **IB\_User\_Data** – This parameter carries user data not specified in this Recommendation which is interpreted by the Access Function. +- **Reference** – This parameter carries a reference value as given by a previously received SBV\_Channel\_Open Indication. This parameter shall not be present when no reference value is available (see 7.3.1). +- **Reverse\_Role\_Assignment** – This parameter has no value. When present, it shall act as an indicator that the calling side requests to reverse the default role assignment (i.e. the calling side requests to act as the Access Function instead of the Terminal Function). The inverted role assignment applies upon a “Successful” confirmation. A called side which is not able to support a reversed role assignment may choose to ignore or reject the incoming call. +- **Result** – This parameter carries the result of the communication establishment; it may take the value “Successful” or, in the case of an attempt to establish a communication with a Videotex Application directly via the Access Function, it may take the value “Application not available” if the communication to the Access Function has been successfully established, but the indicated Videotex Application could not be reached. + +NOTE 4 – This parameter may only be present if the CCITT Recommendation X.25 [5] Fast Select facility is used (see 11.3). + +NOTE 5 – In no case this parameter can be used to indicate that the SBV\_Establish was entirely not successful. The Access Function will indicate this by using SBV\_Release. + +## 7.2.2 SBV\_Release + +The SBV\_Release service shall be used either to release a communication or to indicate that a previous attempt to establish a connection using the SBV\_Establish service has not been successful. It may be initiated by both sides at any time. Moreover, in case of an Access Network failure, both sides shall receive an SBV\_Release indication. In the case of the release of a “Master”-channel, all the associated “Slave”-channels shall be released (see 6.2). + +This service is non-confirmed. The primitives and parameters of the SBV\_Release service are described in Table 4 below. + +TABLE 4/T.105 + +| Parameters | Request | Indication | +|-------------------------------------------------------------------------------------|----------|------------| +| OB_Cause | Optional | Optional | +| IB_Cause | Optional | Optional | +| IB_Diagnostic | Optional | Optional | +| Result | Optional | Optional | +| NOTE – Either OB_Cause or IB_Cause/IB_Diagnostic shall be present in an Indication. | | | + +**Parameters:** + +- **OB\_Cause** – This parameter carries information about the reason for the Out-Band release of the communication. +- **IB\_Cause** – This parameter carries the reason for the In-Band release of the communication. +- **IB\_Diagnostic** – This parameter carries additional information on the reason for the In-Band release of the communication. +- **Result** – This parameter carries the application dependent reason for the release of the communication; it may take the values “Application not available” or “Application already engaged” as the result of a previous attempt to establish a communication with a Videotex Application directly via the Access Function. + +NOTE – This parameter can only appear if the CCITT Recommendation X.25 [5] Fast Select facility is used. + +**7.2.3 SBV\_Reset** + +The SBV\_Reset service element shall be used by the Access Function to reset the Terminal Function into the basic state as defined in Annex C (normative). In addition, all possibly existent “Slave”-channels (see 6.2) related to the communication channel on which the service request was received shall be released. This service is confirmed. + +The primitives and parameters of the SBV\_Reset service are described in Table 5 below. + +TABLE 5/T.105 + +| Parameters | Request | Indication | Response | Confirm | +|----------------------------------------------------------------------------------------------------------------------------------------|---------|------------|-----------------------|--------------------------| +| Result | – | – | Conditional

C1 | Conditional
(=)
C1 | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request or Response primitive. | | | | | + +**Parameters:** + +- **Result** – This parameter carries the result of the SBV\_Reset; it may take the value “Successful” or “Not successful”. + +NOTE – As defined by the condition C1, this parameter is used in case of mapping on Telematic Command (see 8.3.3). + +The condition C1 depends on the application layer to BIS association (see 8.3.3). The value of the condition C1 is defined by Table 6 below. + +TABLE 6/T.105 + +| | | +|--------------------------------------------------------|-----------| +| Mapping of SBV_Reset service on BIS service (Table 22) | C1 | +| SBV_Reset is mapped on a BIS-N-RESET | Excluded | +| SBV_Reset is mapped on a BIS-N-Q-DATA | Mandatory | + +#### 7.2.4 SBV\_VTX\_Data + +This service element shall be used to transfer Videotex data. It may be initiated by both sides. This service is non-confirmed. The primitives and parameters of the SBV\_VTX\_Data service are described in the Table 7 below. + +TABLE 7/T.105 + +| Parameters | Request | Indication | +|----------------------------------------------------------------------------------------------------------------------------|-----------|---------------| +| VTX_Data | Mandatory | Mandatory (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive. | | | + +##### Parameters: + +- **VTX\_Data** – This parameter carries the Videotex data to be transmitted. + +#### 7.2.5 X.3 parameter manipulation services + +##### 7.2.5.1 SBV\_Set\_Param + +This service element shall be used to set one or more of the CCITT Recommendation X.3 [3] parameters of the Terminal Function. It may be initiated by the Access Function only. This service is non-confirmed. The primitives and parameters of the SBV\_Set\_Param service are described in Table 8 below. + +TABLE 8/T.105 + +| Parameters | Request | Indication | +|----------------------------------------------------------------------------------------------------------------------------|----------|--------------| +| X.3_Parameter_List | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive. | | | + +##### Parameters: + +- **X.3\_Parameter\_List** – This parameter carries the X.3 [3] parameter(s) to be modified. + +##### 7.2.5.2 SBV\_Read\_Param + +This service element shall be used to read one or more of the CCITT Recommendation X.3 [3] parameters of the Terminal Function. It may be initiated by the Access Function only. This service is non-confirmed. The primitives and parameters of the SBV\_Read\_Param service are described in Table 9 below. + +TABLE 9/T.105 + +| Parameters | Request | Indication | +|----------------------------------------------------------------------------------------------------------------------------|----------|--------------| +| X.3_Parameter_List | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive. | | | + +##### Parameters: + +- **X.3\_Parameter\_List** – This parameter carries the X.3 parameter(s) to be read. + +### 7.2.5.3 SBV\_Set\_Read\_Param + +This service element shall be used to set one or more of the CCITT Recommendation X.3 [3] parameters of the Terminal Function and to read the indicated parameters. It may be initiated by the Access Function only. This service is non-confirmed. The primitives and parameters of the SBV\_Set\_Read\_Param service are described in Table 10 below. + +TABLE 10/T.105 + +| Parameters | Request | Indication | +|----------------------------------------------------------------------------------------------------------------------------|----------|--------------| +| X.3_Parameter_List | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive. | | | + +#### Parameters: + +- **X.3\_Parameter\_List** – This parameter carries the X.3 [3] parameter(s) to be modified. + +### 7.2.5.4 SBV\_Param\_Ind + +This service element shall be used to indicate the CCITT Recommendation X.3 [3] parameters values of the Terminal Function. It may be initiated by the Terminal Function only. This service is non-confirmed. The primitives and parameters of the SBV\_Param\_Ind service are described in Table 11 below. + +TABLE 11/T.105 + +| Parameters | Request | Indication | +|----------------------------------------------------------------------------------------------------------------------------|----------|--------------| +| X.3_Parameter_List | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive. | | | + +#### Parameters: + +- **X.3\_Parameter\_List** – This parameter carries the X.3 [3] parameter(s) as defined by CCITT Recommendation X.29 [6]. + +### 7.2.6 SBV\_TFI + +The SBV\_TFI service shall be used by the Access Function only to request for the facilities of the Terminal Function. This service is confirmed. The primitives and parameters of the SBV\_TFI service are described in Table 12 below. + +TABLE 12/T.105 + +| Parameters | Request | Indication | Response | Confirm | +|----------------------------------------------------------------------------------------------------------------------------------------|-----------|---------------|-----------|---------------| +| TFI_Enq | Mandatory | Mandatory (=) | – | – | +| TFI_Ack | – | – | Mandatory | Mandatory (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request or Response primitive. | | | | | + +**Parameters:** + +- **TFI\_Enq** – This parameter carries the TFI request data. +- **TFI\_Ack** – This parameter carries the TFI response data. + +### 7.2.7 SBV\_TC\_Error + +The SBV\_TC\_Error service shall be used by the Application Layer itself to indicate to the application that the previously received Telematic Command was erroneous (syntactical error or SBV\_Service not supported or inopportune incoming PDU). This service is non-confirmed. The primitives and parameters of the SBV\_TC\_Error service are described in Table 13 below. + +NOTE – As defined in 8.2.7, a TC\_Error\_PDU is never an inopportune incoming PDU, in the sense of this protocol. It therefore does never cause another TC\_Error\_PDU, but acts as a (negative) response PDU. + +TABLE 13/T.105 + +| Parameters | Request | Indication | +|--------------------------|---------|------------| +| Error_Detection_Location | – | Mandatory | +| Error_Code | – | Mandatory | + +**Parameters:** + +- **Error\_Detection\_Location** – This parameter contains the information whether the error has been detected by the local or the remote Application Layer. +- **Error\_Code** – This parameter carries information about the reason of the error in the Telematic Command or indicates that the previously received Telematic Command is not supported. + +## 7.3 Optional services + +### 7.3.1 Communication channel management services + +The following service elements allows an Access Function to request the Terminal Function to establish or release additional communication channels. If implemented, all communication channel management services shall be supported. + +The additional communication channels may be **independent** from or **linked** with the communication channels which carried the request to open them. The distinction between the two types of additional communication channels is possible by using the Reference parameter of the SBV\_Channel\_Open service: + +- **Independent additional communication channel** – No Reference parameter shall be present in the SBV\_Channel\_Open Request. +- **Linked additional communication channel** – A Reference parameter shall be present in the SBV\_Channel\_Open service. In that case, the requesting communication channel shall be named a “Master”-channel and the requested communication channel (when opened) shall be named a “Slave”-channel. + +The reference value carried in the Reference parameter shall be associated to one and only one opened “Slave”-channel. When the “Slave”-channel has been established by the Terminal Function, the reference value used to establish this communication channel shall be no longer available. + +### 7.3.1.1 SBV\_Channel\_Open + +This service element shall be used by the Access Function to invite the Terminal Function to open an additional communication channel. The opening of the additional communication channel is accomplished by using the SBV\_Establish service. The SBV\_Channel\_Open service is confirmed. The primitives and parameters of the SBV\_Channel\_Open service are described in Table 14 below. + +TABLE 14/T.105 + +| Parameters | Request | Indication | Response | Confirm | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|--------------|-----------|---------------| +| Req_OB_Called_Address | Optional | Optional (=) | – | – | +| Req_OB_Called_Subaddress | Optional | Optional (=) | – | – | +| OB_Application_Address | Optional | Optional (=) | – | – | +| OB_Application_Selection | Optional | Optional (=) | – | – | +| OB_Application_Data | Optional | Optional (=) | – | – | +| Req_OB_User_Data | Optional | Optional (=) | – | – | +| Ind_OB_Cause | – | – | Optional | Optional (=) | +| Req_IB_Called_Address | Optional | Optional (=) | – | – | +| IB_Application_Address | Optional | Optional (=) | – | – | +| IB_Application_Selection | Optional | Optional (=) | – | – | +| IB_Application_Data | Optional | Optional (=) | – | – | +| Req_IB_User_Data | Optional | Optional (=) | – | – | +| Packet_Size | Optional | Optional (=) | – | – | +| Window_Size | Optional | Optional (=) | – | – | +| Ind_IB_Cause | – | – | Optional | Optional (=) | +| Ind_IB_Diagnostic | – | – | Optional | Optional (=) | +| Reference | Optional | Optional (=) | – | – | +| Result | – | – | Mandatory | Mandatory (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request or Response primitive.
NOTE – At least one of the following parameters shall be present in the Request: | | | | | + +## Parameters: + +- **Req\_OB\_Called\_Address** – Carries the Out-Band address of the Access Function to be reached; it can be mapped onto the OB\_Called\_Address parameter of the SBV\_Establish service which shall be used to open the additional communication channel. +- **Req\_OB\_Called\_Subaddress** – Carries the Out-Band subaddress of the Access Function to be reached; it can be mapped onto the OB\_Called\_Subaddress parameter of the SBV\_Establish service. +- **OB\_Application\_Address** – Carries complementary information about the Videotex Application to be reached; it can be mapped onto the OB\_Application\_Address parameter of the SBV\_Establish service. +- **OB\_Application\_Selection** – Carries complementary information (e.g. mnemonic) about the Videotex Application to be reached; it can be mapped onto the OB\_Application\_Selection parameter of the SBV\_Establish. +- **OB\_Application\_Data** – Carries data to be passed to the Videotex Application to be reached; it can be mapped onto the OB\_Application\_Data parameter of the SBV\_Establish. +- **Req\_OB\_User\_Data** – Carries data to be passed transparently to the requested Application; it can be mapped onto the OB\_User\_Data parameter of the SBV\_Establish service. +- **Ind\_OB\_Cause** – Carries the reason for the unsuccessful additional Out-Band communication channel establishment; it corresponds to the OB\_Cause parameter of the SBV\_Release service. +- **Req\_IB\_Called\_Address** – This parameter carries either the address of the Videotex Application or the In-Band address of the Access Function to be reached; it can be mapped onto the IB\_Called\_Address parameter of the SBV\_Establish service which shall be used to open the additional communication channel. +- **IB\_Application\_Address** – This parameter carries complementary information about the Videotex Application to be reached; it can be mapped onto the IB\_Application\_Address parameter of the SBV\_Establish service. +- **IB\_Application\_Selection** – Carries complementary information (e.g. mnemonic) about the Videotex Application to be reached; it can be mapped onto the IB\_Application\_Selection parameter of the SBV\_Establish service. +- **IB\_Application\_Data** – Carries data to be passed to the Videotex Application to be reached; it can be mapped onto the IB\_Application\_Data parameter of the SBV\_Establish service. +- **Req\_IB\_User\_Data** – Carries data to be passed transparently to the requested Application; it can be mapped onto the IB\_User\_Data parameter of the SBV\_Establish service. +- **Packet\_Size** – Carries a requested Layer 3 packet size for the establishment of the additional communication channel. If the requested value is not available for any reason, the value which is currently in use on the requesting channel may be employed instead. +- **Window\_Size** – Carries a requested Layer 3 window size for the establishment of the additional communication channel. If the requested value is not available for any reason, the value which is currently in use on the requesting channel may be employed instead. + +- **Ind\_IB\_Cause** – Carries the reason for the unsuccessful additional In-Band communication channel establishment; it corresponds to the IB\_Cause parameter of the SBV\_Release service. +- **Ind\_IB\_Diagnostic** – Carries additional information about the reason for the unsuccessful additional In-Band communication channel establishment; it corresponds to the IB\_Diagnostic parameter of the SBV\_Release service. +- **Reference** – Carries a reference information to be sent transparently to the Videotex Application to be reached; this parameter can be mapped onto the Reference parameter of the SBV\_Establish service. +- **Result** – Carries the result of the opening of the additional communication channel; it may take the values “Successful”, “Not successful” or “Application not available”. + +If the Result parameter value is “Successful”, no Ind\_OB\_Cause, Ind\_IB\_Cause or Ind\_IB\_Diagnostic parameters shall be present. + +### 7.3.1.2 SBV\_Channel\_Close + +The SBV\_Channel\_Close service element shall be used by the Access Function only to request the release of a previously opened additional “Slave”-channel. Only the request of a channel to release one of its associated “Slave”-channels shall be considered as valid; the release is accomplished by using the SBV\_Release service. All other requests shall result in a negative confirmation but shall be otherwise ignored. + +This SBV\_Channel\_Close service is confirmed. The primitives and parameters of the SBV\_Channel\_Close service are described in Table 15 below. + +TABLE 15/T.105 + +| Parameters | Request | Indication | Response | Confirm | +|----------------------------------------------------------------------------------------------------------------------------------------|-----------|---------------|-----------|---------------| +| Reference | Mandatory | Mandatory (=) | – | – | +| Result | – | – | Mandatory | Mandatory (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request or Response primitive. | | | | | + +#### Parameters: + +- **Reference** – This parameter carries the reference of the communication channel to be closed; it takes the value of the Reference parameter of the SBV\_Channel\_Open service element previously used to request the establishment of the linked additional communication channel. +- **Result** – This parameter carries the result of the release; it may take the value “Successful” if the Release succeeded or “Illegal Reference parameter” if the Reference parameter was erroneous; it may also take the value “Release not allowed” in case of a “Slave”-channel trying to request the closure of its “Master”-channel. + +### 7.3.1.3 SBV\_Channel\_Error + +The SBV\_Channel\_Error service shall be used by the Terminal Function only to inform the Access Function via the “Master”-channel that a previously opened “Slave”-channel has been disconnected for some reason. This service is non-confirmed. The primitives and parameters of the SBV\_Channel\_Error service are described in Table 16 below. + +TABLE 16/T.105 + +| Parameters | Request | Indication | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------|---------------| +| Reference | Mandatory | Mandatory (=) | +| Ind_OB_Cause | Optional | Optional (=) | +| Ind_IB_Cause | Optional | Optional (=) | +| Ind_IB_Diagnostic | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive.
NOTE – Either Ind_OB_Cause or Ind_IB_Cause/Ind_IB_Diagnostic shall be present in an Indication. | | | + +**Parameters:** + +- **Reference** – This parameter carries the reference of the disconnected communication channel; it takes the value of the Reference parameter of the SBV\_Channel\_Open service element previously used to open the linked additional communication channel. +- **Ind\_OB\_Cause** – This parameter carries the reason for the Out-Band disconnection of the referenced communication channel. +- **Ind\_IB\_Cause** – This parameter carries the reason for the In-Band disconnection of the referenced communication channel. +- **Ind\_IB\_Diagnostic** – This parameter carries additional information on the reason for the In-Band disconnection of the referenced communication channel. + +**7.3.2 Application selection services****7.3.2.1 SBV\_Begin\_Application** + +The SBV\_Begin\_Application service shall be used by the Terminal Function only to select a Videotex Application directly by short-cutting the dialogue and welcome phase in the Access Function. If a connection to another Videotex Application existed prior to the use of this service, then this connection may be closed (depending on the Videotex Service definition) by the Access Function before trying to establish the requested connection. This service is confirmed. + +NOTE – This service does not preclude a direct application selection using the SBV\_Establish service. + +The primitives and parameters of the SBV\_Begin\_Application service are described in Table 17 below. + +TABLE 17/T.105 + +| Parameters | Request | Indication | Response | Confirm | +|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------|--------------|-----------|---------------| +| IB_Application_Address | Optional | Optional (=) | – | – | +| IB_Application_Selection | Optional | Optional (=) | – | – | +| IB_Application_Data | Optional | Optional (=) | – | – | +| IB_User_Data | Optional | Optional (=) | – | – | +| Result | – | – | Mandatory | Mandatory (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request or Response primitive.
NOTE – At least one of the following parameters shall be present in the Request: | | | | | + +#### Parameters: + +- **IB\_Application\_Address** – This parameter carries the address of the Videotex Application to be reached; it is interpreted by the Access Function in order to establish the communication with the requested Application. +- **IB\_Application\_Selection** – This parameter carries information (e.g. mnemonic) about the Videotex Application to be reached; it is interpreted by the Access Function in order to establish the communication with the requested Application. +- **IB\_Application\_Data** – This parameter carries data to be passed transparently by the Access Function to the Videotex Application to be reached. +- **IB\_User\_Data** – This parameter carries data not specified in this Recommendation to be interpreted by the Access Function. +- **Result** – This parameter carries the result of the direct access to the Application; it may take the value “Successful”, “Application not available” if the requested Videotex Application is not available or “Application already engaged” for those Access Functions which are not able to disconnect from an engaged application upon reception of an SBV\_Begin\_Application indication. + +#### 7.3.2.2 SBV\_End\_Application + +The SBV\_End\_Application service shall be used by the Terminal Function only to disconnect from a Host Function and to return to a dialogue and welcome phase. This service is non-confirmed. + +#### Parameters: + +None. + +#### 7.3.2.3 SBV\_End\_Immediate + +The SBV-End\_Immediate service shall be used by the Terminal Function only to disconnect from a Host Function as soon as possible and return to a dialogue and welcome phase. There is a risk of loss of intermediate data. This service is non-confirmed. + +#### Parameters: + +None. + +### 7.3.3 Transparent processable data services + +The SBV\_TPD (Transparent Processable Data) services may be used to allow for the exchange of processable data (see Rec. T.101 [8], DS II) transparently without making use of the Dialogue Data Units (DDUs). If implemented, both transparent processable data services (SBV\_TPD\_Begin and SBV\_TPD\_End) shall be supported. + +#### 7.3.3.1 SBV\_TPD\_Begin + +The SBV\_TPD\_Begin service shall be used to request for the exchange of transparent processable data. It may be initiated by both sides. This service is confirmed. The primitives and parameters of the SBV\_TPD\_Begin service are described in Table 18 below. + +TABLE 18/T.105 + +| Parameters | Request | Indication | Response | Confirm | +|----------------------------------------------------------------------------------------------------------------------------------------|---------|------------|-----------|---------------| +| Result | – | – | Mandatory | Mandatory (=) | +| DDU_Fall-Back_Mode | – | – | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request or Response primitive. | | | | | + +#### Parameters: + +- **Result** – This parameter carries the information whether the receiving side shall support the transparent transmission of processable data or not. It may take the values “Successful” or “TPD not supported”. + +If the Result parameter takes the value “Successful”, then the processable data shall be exchanged transparently and the following application rules shall apply: + +- The DDU Layer shall not be used. +- A T-Associate request shall be issued immediately upon the receipt of an SBV\_TPD\_Begin Confirmation indicating “Successful”. +- A TDU is carried in one single complete packet sequence of DATA packets with the Q-bit set to 0. +- A complete packet sequence may contain one and only one TDU. +- 8-bit processable data are exchanged via DATA packets with the Q-bit set to 0. +- The regime of an SBV\_TPD\_Begin lasts up to the transmission of an SBV\_TPD\_End Request. + +If the Result parameter takes the value “TPD not supported”, then the processable data shall be exchanged as defined in Recommendation T.101 [8], DS II using the SBV\_VTX\_Data service, if possible. The regime of transparent processable data exchange shall be implicitly terminated. + +- **DDU\_Fall-Back\_Mode** – This parameter may be present if the value of the Result parameter indicates “TPD not supported”. It may give additional information about supported DDU modes on the receiving side. This parameter may take values from “A” to “G” and their permitted combinations (see 9.3.3.2), corresponding to the respective DDU modes as specified in Recommendation T.101 [8]. + +#### 7.3.3.2 SBV\_TPD\_End + +The SBV\_TPD\_End service shall be used to end the regime of a previously established transparent processable data exchange. This service is non-confirmed. + +The receipt of an SBV\_TPD\_End indication shall release any possibly pending T-Associate regime in the sense of Recommendation T.101 [8]. + +#### Parameters: + +None. + +#### 7.3.4 SBV\_DFK + +The SBV\_DFK (Definable Function Keys) service shall be used to define function keys. It shall be initiated by the Access Function only. This service is non-confirmed. The primitives and parameters of the SBV\_DFK service are described in Table 19 below. + +TABLE 19/T.105 + +| Parameters | Request | Indication | +|----------------------------------------------------------------------------------------------------------------------------|----------|--------------| +| Function_Keys | Optional | Optional (=) | +| Reset_Keys | Optional | Optional (=) | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive. | | | + +#### Parameters: + +At least one of the parameters should be used. If no parameter is present in an SBV\_DFK Request, the service primitive shall be ignored. + +- **Reset\_Keys** – This parameter indicates that all definable function keys set by a previous SBV\_DFK invocation are to be cleared. Forwarding conditions set by CCITT Recommendation X.3 [3] set commands are not influenced by this reset mechanism. +- **Function\_Keys** – This parameter carries a list of function key definitions. Each function key definition consists of an identification, a user-visible name, an indication whether pressing the function key shall be a forwarding condition, and a code sequence (a sequence of octets which has to be sent to the Access Function when the forwarding condition occurs). + +#### 7.3.5 SBV\_Remote\_Echo + +The SBV\_Remote\_Echo shall be used by the Terminal-Function only to request the Access Function to stop or to start the echo. This service is non-confirmed. The primitive and parameter of the SBV\_Remote\_Echo service are described in Table 20 below. + +NOTE – In some cases the AF may not be able to fulfil the request (e.g. when waiting for a user to select a new page, the AF might not be prepared to switch echo off). + +TABLE 20/T.105 + +| Parameters | Request | Indication | +|------------|-----------|---------------| +| Echo | Mandatory | Mandatory (=) | + +#### Parameters: + +- **Echo** – This parameter carries information about the echo management. It may take the value “ON” or “OFF”. + +#### 7.3.6 SBV\_Escape + +The SBV\_Escape service is used for functions which exist in some Videotex Services (e.g. bulk update, transport of binary data). For details concerning this service refer to Annex D (informative). This service is non-confirmed. The primitives and parameters of the SBV\_Escape service are described in Table 21 below. + +TABLE 21/T.105 + +| Parameters | Request | Indication | +|----------------------------------------------------------------------------------------------------------------------------|-----------|---------------| +| Service_ID | Mandatory | Mandatory (=) | +| Data | Optional | Optional | +| (=) The value of this parameter is identical to the one of the corresponding parameter in the preceding Request primitive. | | | + +#### Parameters: + +- **Service-ID** – This parameter carries the identification of a specific service [see 9.1 and Annex D (informative)]. +- **Data** – This parameter carries data not standardized in this Recommendation. + +## 8 Protocol + +### 8.1 Association of SBV Application Layer and BIS primitives + +Table 22 shows the association between SBV application layer PDUs and BIS primitives (see clause 11). For each application layer PDU the corresponding BIS primitive is given. + +TABLE 22/T.105 + +#### Association of SBV application layer and BIS + +| SBV Application Layer PDU | SBV_NL Primitives | Allowed primitive type | | +|--------------------------------------------------------------------------------------------|---------------------|------------------------|-----------| +| | | Req./Ind. | Rsp./Con. | +| SBV_Establish | BIS-N-CONNECT | X | X | +| SBV_Release | BIS-N-DISCONNECT | X | | +| SBV_Reset | BIS-N-RESET or | X | X | +| | BIS-N-Q-DATA (Note) | X | X | +| SBV_VTX_Data | BIS-N-DATA | X | | +| SBV_Set_Param | BIS-N-Q-DATA | X | | +| SBV_Read_Param | BIS-N-Q-DATA | X | | +| SBV_Set_Read_Param | BIS-N-Q-DATA | X | | +| SBV_Param_Ind | BIS-N-Q-DATA | X | | +| SBV_TFI | BIS-N-Q-DATA | X | X | +| SBV_TC_Error | BIS-N-Q-DATA | X | | +| SBV_Channel_Open | BIS-N-Q-DATA | X | X | +| SBV_Channel_Close | BIS-N-Q-DATA | X | X | +| SBV_Channel_Error | BIS-N-Q-DATA | X | | +| SBV_Begin_Application | BIS-N-Q-DATA | X | X | +| SBV_End_Application | BIS-N-Q-DATA | X | | +| SBV_End_Immediate | BIS-N-INTERRUPT | X | | +| SBV_TPD_Begin | BIS-N-Q-DATA | X | X | +| SBV_TPD_End | BIS-N-Q-DATA | X | | +| SBV_DFK | BIS-N-Q-DATA | X | | +| SBV_Remote_Echo | BIS-N-Q-DATA | X | | +| SBV_Escape | BIS-N-Q-DATA | X | X | +| Req. Request
Ind. Indication
Rsp. Response
Con. Confirmation
NOTE – See 8.2.3. | | | | + +## 8.2 Procedures + +Except for the SBV\_Establish and the SBV\_Release service, all Application Layer service primitives shall be issued only on an established network connection. + +On a given network connection, all confirmed services shall proceed in accordance with the following rules: + +- After having issued a Request-PDU, the application layer shall not issue any other PDU (except for the SBV\_Release-Request-PDU or the SBV\_Reset-Request-PDU or the TC\_Error-PDU) before the reception of the Response-PDU. +- Upon reception of a Request-PDU, the application layer shall not issue any other PDU (except for the SBV\_Release-Request-PDU or the SBV\_Reset-Request-PDU) than the Response-PDU to the requested service. +- After the reception of a Request-PDU, any reception of another Request-PDU (except for the SBV\_Release-Request-PDU or the SBV\_Reset-Request-PDU) before the issuing of the Response shall be treated as an SBV-protocol error. +- An SBV-protocol error detected by the application layer will cause a TC\_Error-PDU send by the application layer to the remote application layer. This TC\_Error-PDU replaces the outstanding Response-PDU, which shall not be issued by the application layer even if the Response Primitive already occurred at the upper service interface. +- After having issued a Request-PDU, the reception of either an SBV\_Release-Request-PDU or an SBV\_Reset-Request-PDU or a TC\_Error-PDU implicitly results in a (negative) confirmation. +- At the issuing time of confirmed service Request-PDU, a timer shall be started; when the timer runs out and the Response-PDU has not been received, the communication shall be released. + +The initial value of this timer shall not be smaller than timer value T28 multiplied by counter value R28 as defined in ISO 8208 [15]. + +NOTE – It is a local matter and therefore out of scope for the protocol definition, how the requirements given above are fulfilled locally, e.g. with respect to the upper service interface, its primitives and its user application. + +CCITT Recommendation X.29 [6] related protocol errors (e.g. unrecognizable X.29 messages) shall be treated in accordance to CCITT Recommendation X.29 [6]. + +Protocol errors related to Telematic Commands shall be treated by the protocol as defined in this Recommendation. + +### 8.2.1 SBV\_Establish + +No additional procedures defined. + +NOTE – As there is no “negative” SBV\_Establish response PDU, an SBV\_Release request PDU will occur when the communication cannot be established. + +### 8.2.2 SBV\_Release + +No additional procedures defined. + +### 8.2.3 SBV\_Reset + +A terminal function shall perform the SBV\_Reset service when receiving either a DTE originated BIS\_N\_RESET indication or an SBV\_Reset\_TC or both. + +NOTE – Terminals conforming to T.105 as per COM VIII-R 47 (1992) react to an SBV\_Reset\_TC by sending an SBV\_Error\_TC. + +### 8.2.4 SBV\_VTX\_Data + +No additional procedures defined. + +## **8.2.5 X.3 parameter manipulation services** + +The detailed procedures to set and/or read one or more of the available CCITT Recommendation X.3 [3] parameters or extended parameters (see clause 10) of the Terminal Function are described in the CCITT Recommendation X.29 [6], 1.5, 3.1 and 3.5.1. + +Protocol errors related to these services (e.g. erroneous X.29 PAD messages) shall be treated in accordance to CCITT Recommendation X.29 [6]. + +### **8.2.5.1 SBV\_Set\_Param** + +No additional procedures defined. + +### **8.2.5.2 SBV\_Read\_Param** + +No additional procedures defined. + +### **8.2.5.3 SBV\_Set\_Read\_Param** + +No additional procedures defined. + +### **8.2.5.4 SBV\_Param\_Ind** + +No additional procedures defined. + +## **8.2.6 SBV\_TFI** + +No additional procedures defined. + +## **8.2.7 SBV\_TC\_Error** + +An SBV\_TC\_Error PDU is sent by the Application Layer when a previously received Telematic Command PDU was either not supported or erroneous. This does not apply for any previously received TC\_Error PDU (regardless whether their parameters are valid or not). At the same time, a TC\_Error\_Indication is given to the local application with the Error\_Detection\_Location parameter set to "local". + +A valid incoming SBV\_TC\_Error\_TC PDU results in an SBV\_TC\_Error Indication primitive with the Error\_Detection\_Location parameter set to "remote". + +## **8.2.8 Communication channel management services** + +The procedures below apply only if the communication channel management services are implemented. + +### **8.2.8.1 SBV\_Channel\_Open** + +Upon reception of a valid SBV\_Channel\_Open request PDU, the Terminal Function doubles the instance (see Figure 2) and transmits an SBV\_Establish request PDU on the new instance. After the reception of SBV\_Establish response PDU or an SBV\_Release PDU, the Terminal Function shall issue the SBV\_Channel\_Open response PDU which shall reflect the result of the attempted connection establishment. + +### **8.2.8.2 SBV\_Channel\_Close** + +Upon reception a valid SBV\_Channel\_Close request PDU, the contained Reference parameter shall be inspected. + +The forwarded reference value shall be considered as invalid, if: + +- there is no communication channel associated to the reference value; +- the associated communication channel is not a Slave-channel in relation to the communication channel on which the SBV\_Channel\_Close indication has been received. + +If the reference value is invalid, the Terminal Function issues an SBV\_Channel\_Close response PDU with the Result parameter set accordingly. + +If the Reference parameter is valid, the Terminal Function shall transmit an SBV\_Release request PDU on the network connection associated to the Reference parameter. The Terminal Function shall then issue an SBV\_Channel\_Close response PDU positive with the appropriate value in the Result parameter. + +### **8.2.8.3 SBV\_Channel\_Error** + +No additional procedures defined. + +## **8.2.9 Application selection services** + +### **8.2.9.1 SBV\_Begin\_Application** + +No additional procedures defined. + +### **8.2.9.2 SBV\_End\_Application** + +No additional procedures defined. + +### **8.2.9.3 SBV\_End\_Immediate** + +No additional procedures defined. + +## **8.2.10 Transparent processable data services** + +### **8.2.10.1 SBV\_TPD\_Begin** + +If the Result parameter in an SBV\_TPD\_Begin response PDU is set to “TPD not supported” the regime for the exchange of transparent processable data is implicitly terminated. + +### **8.2.10.2 SBV\_TPD\_End** + +The reception of an SBV\_TPD\_End\_TC request PDU terminates the regime for the exchange of transparent processable data. An SBV\_TPD\_End\_TC request PDU may occur even if there is no Regime activated by the SBV\_TPD\_Begin Service used recently. + +### **8.2.11 SBV\_DFK** + +The reception of an otherwise valid SBV\_DFK request PDU which contains a reference to a function key which is not supported shall result in the transmission of an SBV\_TC\_Error response PDU indicating “TC erroneous”. + +### **8.2.12 SBV\_Remote\_Echo** + +No additional procedures defined. + +### **8.2.13 SBV\_Escape** + +No additional procedures defined. + +## **8.3 Mapping of parameters** + +The following Tables 23 to 44 contain the mappings between the parameters of the higher layer service primitives and the parameters of the BIS primitives. + +An Application Layer parameter may not be applicable to all forms of a primitive (request, indication, response and confirm). The applicability of the parameters is defined in clause 7 and not repeated here. + +The X.3 parameter manipulating services and the Telematic Commands (SBV\_TFI to SBV\_Escape) make use of only one SBV-IB service primitive, namely BIS-N-Q-DATA. At the higher layers, a discrimination is possible by inspecting the contents of the BIS user data parameter. + +NOTE – The Telematic Commands have assigned a Telematic Command header (see 9.1). It precedes the actual parameters of a Telematic Command, and is used to distinguish between the different Telematic Command service primitives. Although this header is not defined as a parameter at the higher layers, it nevertheless appears in the tables below, because it is carried in the user data parameter of the BIS-N-Q-DATA service. + +### **8.3.1 SBV\_Establish** + +See Table 23. + +### **8.3.2 SBV\_Release** + +See Table 24. + +TABLE 23/T.105 + +**Parameter associations for the SBV\_Establish primitive** + +| SBV_Establish parameters | BIS-N-CONNECT parameters | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------| +| OB_Called_Address | Called/Responding Address | +| OB_Called_Subaddress | Called/Responding Address | +| not used | Calling Address (Note 1) | +| OB_Application_Address | BIS-user-data | +| OB_Application_Selection | BIS-user-data | +| OB_Application_Data | BIS-user-data | +| OB_User_Data | BIS-user-data | +| IB_Called_Address | Called/Responding Address or
BIS-user-data (Note 2) | +| IB_Application_Address | BIS-user-data | +| IB_Application_Selection | BIS-user-data | +| IB_Application_Data | BIS-user-data | +| IB_User_Data | BIS-user-data | +| Reference | BIS-user-data | +| Reverse_Role_Assignment | BIS-user-data | +| Result | BIS-user-data (Note 3) | +|

NOTES

1 This parameter is not processed by the Application Layer.

2 When In-Band Addressing is used (e.g. Recommendation X.31, case A), the SBV_Establish parameter IB_Called_Address is mapped onto the Called/Responding Address parameter of the BIS-N-CONNECT primitive. Otherwise, it is mapped onto BIS-user-data parameter of the BIS-N-CONNECT primitive. Note that the mapping of those two BIS-N-CONNECT parameters onto the same X.25 field in both cases does not contradict this way of description.

3 This parameter can only be used in conjunction with the Recommendation X.25 Fast Select facility.

| | + +TABLE 24/T.105 + +**Parameter associations for the SBV\_Release primitive** + +| SBV_Release parameters | BIS-N-DISCONNECT parameters | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------| +| OB_Cause | Originator, Reason (Note 1) | +| IB_Cause | Originator (Note 2) | +| IB_Diagnostic | Reason (Note 2) | +| Result | BIS-user-data (Note 3) | +|

NOTES

1 When BIS parameters (Originator, Reason) take Out-Band related values.

2 When BIS parameters (Originator, Reason) take In-Band related values.

3 This parameter can only be used in conjunction with the X.25 Fast Select facility.

| | + +### 8.3.3 SBV\_Reset + +Depending on the application layer to BIS association (see Table 22), the mapping of Table 25 or Table 26 applies. + +TABLE 25/T.105 + +#### Parameter associations for the SBV\_Reset (N-Reset) primitive (N-Reset) + +| SBV_Reset parameters | BIS-N-RESET parameters | +|---------------------------------------------------------------------|------------------------------------| +| Not used
Not used | Originator (Note)
Reason (Note) | +| NOTE – These parameters are not processed by the Application Layer. | | + +TABLE 26/T.105 + +#### Parameter associations for the SBV\_Reset primitive (Telematic Command) + +| SBV_Reset parameters | BIS-N-Q-DATA parameters | +|------------------------------------|--------------------------------| +| Telematic command header
Result | BIS-user-data
BIS-user-data | + +### 8.3.4 SBV\_VTX\_Data + +See Table 27. + +TABLE 27/T.105 + +#### Parameter associations for the SBV\_VTX\_Data primitive + +| SBV_VTX_Data parameter | BIS-N-DATA parameter | +|------------------------|----------------------| +| VTX_DATA | BIS-user-data | + +### 8.3.5 X.3 parameter manipulation services + +#### 8.3.5.1 SBV\_Set\_Param + +See Table 28. + +TABLE 28/T.105 + +#### Parameter associations for the SBV\_Set\_Param primitive + +| SBV_Set_Param parameter | BIS-N-Q-DATA parameter | +|-------------------------|------------------------| +| X.3_Parameter_List | BIS-user-data | + +8.3.5.2 SBV\_Read\_Param + +See Table 29. + +TABLE 29/T.105 +Parameter associations for the SBV\_Read\_Param primitive + +| SBV_Read_Param parameter | BIS-N-Q-DATA parameter | +|--------------------------|------------------------| +| X.3_Parameter_List | BIS-user-data | + +8.3.5.3 SBV\_Set\_Read\_Param + +See Table 30. + +TABLE 30/T.105 +Parameter associations for the SBV\_Set\_Read\_Param primitive + +| SBV_Set_Read_Param parameter | BIS-N-Q-DATA parameter | +|------------------------------|------------------------| +| X.3_Parameter_List | BIS-user-data | + +8.3.5.4 SBV\_Param\_Ind + +See Table 31. + +TABLE 31/T.105 +Parameter associations for the SBV\_Param\_Ind primitive + +| SBV_Param_Ind parameter | BIS-N-Q-DATA parameter | +|-------------------------|------------------------| +| X.3_Parameter_List | BIS-user-data | + +8.3.6 SBV\_TFI + +See Table 32. + +TABLE 32/T.105 +Parameter associations for the SBV\_TFI primitive + +| SBV_TFI parameters | BIS-N-Q-DATA parameters | +|------------------------------------------------|-------------------------------------------------| +| Telematic command header
TFI_Enq
TFI_Ack | BIS-user-data
BIS-user-data
BIS-user-data | + +### 8.3.7 SBV\_TC\_Error + +See Table 33. + +TABLE 33/T.105 + +#### Parameter associations for the SBV\_TC\_Error primitive + +| SBV_TC_Error parameters | BIS-N-Q-DATA parameters | +|---------------------------------------------------------|--------------------------------| +| Telematic command header
Error_Code | BIS-user-data
BIS-user-data | +| NOTE – The Error_Detection_Location parameter is local. | | + +### 8.3.8 Communication channel management services + +#### 8.3.8.1 SBV\_Channel\_Open + +See Table 34. + +TABLE 34/T.105 + +#### Parameter associations for SBV\_Channel\_Open primitive + +| SBV_Channel_Open parameters | BIS-N-Q-DATA parameters | +|--------------------------------|-------------------------| +| Telematic command header (TCH) | BIS-user-data | +| Req_OB_Called_Address | BIS-user-data | +| Req_OB_Called_Subaddress | BIS-user-data | +| OB_Application_Address | BIS-user-data | +| OB_Application_Selection | BIS-user-data | +| OB_Application_Data | BIS-user-data | +| Req_OB_User_Data | BIS-user-data | +| Ind_OB_Cause | BIS-user-data | +| Req_IB_Called_Address | BIS-user-data | +| IB_Application_Address | BIS-user-data | +| IB_Application_Selection | BIS-user-data | +| IB_Application_Data | BIS-user-data | +| Req_IB_User_Data | BIS-user-data | +| Packet_Size | BIS-user-data | +| Window_Size | BIS-user-data | +| Ind_IB_Cause | BIS-user-data | +| Ind_IB_Diagnostic | BIS-user-data | +| Reference | BIS-user-data | +| Result | BIS-user-data | + +### 8.3.8.2 SBV\_Channel\_Close + +See Table 35. + +TABLE 35/T.105 + +#### Parameter associations for the SBV\_Channel\_Close primitive + +| SBV_Channel_Close parameters | BIS-N-Q-DATA parameters | +|-------------------------------------------------|-------------------------------------------------| +| Telematic command header
Reference
Result | BIS-user-data
BIS-user-data
BIS-user-data | + +### 8.3.8.3 SBV\_Channel\_Error + +See Table 36. + +TABLE 36/T.105 + +#### Parameter associations for the SBV\_Channel\_Error primitive + +| SBV_Channel_Error parameters | BIS-N-Q-DATA parameters | +|--------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------| +| Telematic command header
Reference
Ind_OB_Cause
Ind_IB_Cause
Ind_IB_Diagnostic | BIS-user-data
BIS-user-data
BIS-user-data
BIS-user-data
BIS-user-data | + +### 8.3.9 Application selection services + +#### 8.3.9.1 SBV\_Begin\_Application + +See Table 37. + +TABLE 37/T.105 + +#### Parameter associations for the SBV\_Begin\_Application primitive + +| SBV_Begin_Application parameters | BIS-N-Q-DATA parameters | +|---------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------| +| Telematic command header
IB_Application_Address
IB_Application_Selection
IB_Application_Data
IB_User_Data
Result | BIS-user-data
BIS-user-data
BIS-user-data
BIS-user-data
BIS-user-data
BIS-user-data | + +### 8.3.9.2 SBV\_End\_Application + +See Table 38. + +TABLE 38/T.105 + +#### Parameter associations for the SBV\_End\_Application primitive + +| SBV_End_Application parameter | BIS-N-Q-DATA parameter | +|-------------------------------|------------------------| +| Telematic command header | BIS-user-data | + +### 8.3.9.3 SBV\_End\_Immediate + +See Table 39. + +TABLE 39/T.105 + +#### Parameter associations for the SBV\_End\_Immediate primitive + +| SBV_End_Immediate parameter | BIS-N-INTERRUPT parameter | +|---------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------| +| Not used | BIS-Interrupt-user-data (Value 08/00) | +| NOTE – The SBV_End_Immediate is mapped upon the BIS-N-INTERRUPT primitive with BIS-Interrupt-user-data containing one single byte with the value 08/00. | | + +### 8.3.10 Transparent processable data services + +#### 8.3.10.1 SBV\_TPD\_Begin + +See Table 40. + +TABLE 40/T.105 + +#### Parameter associations for the SBV\_TPD\_Begin primitive + +| SBV_TPD_Begin parameters | BIS-N-Q-DATA parameters | +|----------------------------------------------------------|-------------------------------------------------| +| Telematic command header
Result
DDU_Fall_Back_Mode | BIS-user-data
BIS-user-data
BIS-user-data | + +### 8.3.10.2 SBV\_TPD\_End + +See Table 41. + +TABLE 41/T.105 + +#### Parameter associations for the SBV\_TPD\_End primitive + +| SBV_TPD_End parameter | BIS-N-Q-DATA parameter | +|--------------------------|------------------------| +| Telematic command header | BIS-user-data | + +### 8.3.11 SBV\_DFK + +See Table 42. + +TABLE 42/T.105 + +#### Parameter associations for the SBV\_DFK primitive + +| SBV_DFK parameters | BIS-N-Q-DATA parameters | +|---------------------------------------------------------|-------------------------------------------------| +| Telematic command header
Function_Keys
Reset_Keys | BIS-user-data
BIS-user-data
BIS-user-data | + +### 8.3.12 SBV\_Remote\_Echo + +See Table 43. + +TABLE 43/T.105 + +#### Parameter associations for the SBV\_Remote\_Echo primitive + +| SBV_Remote_Echo parameters | BIS-N-Q-DATA parameters | +|----------------------------------|--------------------------------| +| Telematic command header
Echo | BIS-user-data
BIS-user-data | + +### 8.3.13 SBV\_Escape + +See Table 44. + +TABLE 44/T.105 + +#### Parameter associations for the SBV\_Escape primitive + +| SBV_Escape parameters | BIS-N-Q-DATA parameters | +|-----------------------------------------------------------------------------------------------------------|-------------------------------------------------| +| Telematic command header
Service-ID (Note)
Data | BIS-user-data
BIS-user-data
BIS-user-data | +| NOTE – The Service-ID parameter corresponds to the third octet of the telematic command header (see 9.1). | | + +## 9 Coding + +### 9.1 Coding of the Telematic Command PDUs + +Telematic Command PDUs are carried in the BIS user data parameter of the BIS-N-Q-DATA primitive. The Telematic Command PDU consists of a Telematic command header (TCH) of four bytes, immediately followed by the Telematic command message (TCM). + +The first octet carried of the TCH shall be coded 04/00. + +NOTE 1 – This value is described in CCITT Recommendation X.29 (92), 4.4.1, and indicates “Telematic service message, Videotex”. + +The second octet of the TCH shall be coded 09/14, indicating “Syntax-based Videotex Telematic Command”. + +NOTE 2 – Both the protocol defined in this Recommendation and Rec. T.101 [8] make use of CCITT Recommendation X.29 (92) extension “Telematic service message, Videotex”. The value 09/14 corresponds to “tag [30]” as reserved for the Syntax-based Videotex Terminal protocol. + +The third octet shall contain the codepoint identifying the Telematic Command. The range of the Telematic Command code values carried in this octet is divided into three parts: + +00/00-07/14: used for services defined in this Recommendation; + +08/00-11/14: used for SBV\_Escape subservices; + +12/00-15/15: for private use. + +Both values 07/15 and 11/15 are reserved for future extensions. + +The Telematic Command code values are given in Table 45 below. + +TABLE 45/T.105 + +**Telematic Command code values** + +| Telematic Command (Note) | Telematic Command code | +|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|------------------------| +| SBV_TC_Error_TC | 00/01 | +| SBV_Channel_Open_TC | 00/02 | +| SBV_Channel_Close_TC | 00/03 | +| SBV_Channel_Error_TC | 00/04 | +| SBV_TFI_TC | 00/05 | +| SBV_Begin_Application_TC | 00/06 | +| SBV_End_Application_TC | 00/07 | +| SBV_TPD_Begin_TC | 00/08 | +| SBV_TPD_End_TC | 00/09 | +| SBV_DFK_TC | 00/10 | +| SBV_Reset_TC | 00/11 | +| SBV_Remote_Echo_TC | 00/12 | +| NOTE – Octet 3 can directly indicate the purpose of the command. In that case, it corresponds to the Service-ID parameter of the SBV_Escape service [see Annex D (informative)]. | | + +The fourth octet carries the total length of the subsequent Telematic Command Message. This length may be in the range from 0 (00/00) to 254 (15/14). The value 255 (15/15) is reserved for future extensions. + +The TCM shall start on the fifth octet of the TC PDU. It carries the sub-fields associated to the parameters of the Telematic Command. For certain Telematic Commands, the TCM may be empty. + +A summary of the structure of the TC PDU is given in Figure 5. + +| | | +|---------|------------| +| Octet 1 | 04/00 | +| Octet 2 | 09/14 | +| Octet 3 | TC code | +| Octet 4 | TC length | +| Octet 5 | TC message | +| . | . | +| . | . | +| . | . | + +FIGURE 5/T.105 + +## Coding and structure of a Telematic Command PDU + +### 9.2 Coding structures + +The coding of the various sub-fields associated to the parameters given in Table 46 (see 9.3.1) uses a Type, Length, Value (TLV) method. This coding scheme offers a basic structure and an extended structure. It is applicable to parameters which are carried in the user data fields of the BIS-N-CONNECT and BIS-N-DISCONNECT services and to parameters carried in a Telematic Command. + +NOTE – The Basic Coding Structure is necessary due to the limited amount of data which can be carried in the user data fields of the BIS-N-CONNECT service when the X.25 Fast Select facility is not used. However, to encode the different parameters carried in one service element, it may be necessary to employ both coding methods, respectively. + +When applying this coding scheme to parameters which are mapped to the user data field of the BIS-N-CONNECT service (regardless whether the X.25 Fast Select facility is used or not), the coding shall start on the fifth octet of the user data field. CCITT Recommendation X.29 [6] reserves the first four octets for the protocol identifier. + +9.2.1 Basic coding structure + +In this coding structure, the type indicator and the length indicator are coded on 4 bits, respectively. The value of the length indicates the length in octets of the following field. Figure 6 gives an overview: + +![Diagram of basic coding structure showing MSB and LSB fields with type and length indicators.](01e00200a536673d6cd0e6d8705047a0_img.jpg) + +The diagram illustrates the basic coding structure. On the left, the MSB (Most Significant Bit) field is shown as a vertical stack of octets: Octet 1, Octet 2, ..., Octet N, ..., Octet N + 1, ..., This field is separated from the LSB (Least Significant Bit) field by a vertical line. The LSB field is a horizontal box divided into four rows. The first row contains 'Type 1' followed by a vertical bar and 'Length 1'. The second row contains 'Value 1' followed by a vertical bar and two dots. The third row contains 'Type M' followed by a vertical bar and 'Length M'. The fourth row contains 'Value M' followed by a vertical bar and two dots. To the right of the LSB field, there are two annotations: 'Length between 0 and 14' next to the first row, and 'Length between 0 and 14' next to the third row. + +Diagram of basic coding structure showing MSB and LSB fields with type and length indicators. + +FIGURE 6/T.105 +Basic coding structure + +The type indicator may take the values: + +- 0-7: not defined in this Recommendation; +- 8-14: defined in this Recommendation; +- 15: reserved for the extended coding structure. + +The length indicator may take values between 0 and 14. + +A value of 15 in the length indicator implies that the following octet represents the actual length of the parameter value. This actual length shall take a value in the range from 15 (00/15) to 127 (07/15). Values greater than 127 (07/15) are reserved for future extensions. + +Figure 7 predicts the coding scheme for that case. + +![Diagram of basic coding structure with length extension mechanism.](b4f6d3668f7e851eaff07ccf26001623_img.jpg) + +The diagram illustrates the basic coding structure with a length extension mechanism. On the left, the MSB (Most Significant Bit) field is shown as a vertical stack of octets: ..., Octet N, ..., Octet N + 1, ..., Octet N + 2, ..., This field is separated from the LSB (Least Significant Bit) field by a vertical line. The LSB field is a horizontal box divided into four rows. The first row contains two dots. The second row contains 'Type M' followed by a vertical bar and '15'. The third row contains 'Length M'. The fourth row contains 'Value M' followed by a vertical bar and two dots. To the right of the LSB field, there is an annotation: 'Length between 15 and 127'. + +Diagram of basic coding structure with length extension mechanism. + +FIGURE 7/T.105 +Basic coding structure with length extension mechanism + +### 9.2.2 Extended coding structure + +If the first octet of a parameter carries the value 255 (15/15), the following octets shall contain an extended type indicator coded in one octet and a length indicator coded in one octet, as presented in Figure 8. + +![](8f7c0bf0c75a31fee6b0c7392ff57c39_img.jpg) + +| MSB | LSB | +|-------------|-----------------| +| . | . | +| . | . | +| Octet N | 15/15 | +| Octet N + 1 | Extended Type M | +| Octet N + 2 | Length M | +| Octet N + 3 | Value M | +| . | . | +| . | . | + +Length +between 0 and 127 + +FIGURE 8/T.105 + +#### Extended coding structure + +The extended type indicator may take the values: + +00/00-07/15: not defined in this Recommendation; + +08/00-15/15: defined in this Recommendation. + +NOTE – In order to avoid any ambiguities between the basic and the extended coding structures, type indicator values x/00 (x in the range from 8 to 15) are reserved for use with the basic coding structure. + +In the extended coding structure, the length indicator may take a value in the range from 0 (00/00) to 127 (07/15). Values greater than 127 are reserved for future extensions. + +### 9.2.3 Coding of data types + +#### 9.2.3.1 Integers + +Integer values shall be coded in one octet. The contents of this octet shall be the binary number equal to the integer value. + +NOTE – Integers coded in more than one octet are for further study. + +#### 9.2.3.2 Strings + +String values shall be coded as a sequence of characters as defined in CCITT Recommendation T.51 [2]. + +#### 9.2.3.3 Voids + +The void data type shall be coded having zero-length and no value. + +#### 9.2.3.4 Octet sequences + +The octet sequence shall be coded as a sequence of arbitrary octets. + +### 9.3 Coding of parameters + +The coding of the following parameters is not performed by the Application Layer, but shall be performed by the BIS: + +- OB\_Called\_Address; +- OB\_Called\_Subaddress; +- OB\_Cause; +- IB\_Cause; +- IB\_Diagnostic. + +Depending on whether In-Band addressing is used or not, the coding of the parameter + +- IB\_Called\_Address + +is performed by either the BIS (with In-Band addressing) or the Application layer (no In-Band addressing). In the latter case, the coding shall be as defined by ISO 8208 [15], subclauses 12.2.1.1.2 and 12.2.1.1.3. + +#### 9.3.1 Coding of user data fields using the coding structures + +Table 46 defines the coding of parameters which are carried in the user data fields of the BIS-N-CONNECT and BIS-N-DISCONNECT services and to parameters carried in a Telematic Command PDU, using the coding structure as defined in 9.2. + +TABLE 46/T.105 + +| Parameter | PDU(s) | Type
BCS | Type
ECS | Value or Remarks | +|--------------------------|------------------------------------------------------------------|-------------|-------------|------------------------------------| +| DDU_Fall-Back_Mode | SBV_TPD_Begin_TC | – | 12/02 | String (9.3.3.2) | +| Error_Code | SBV_TC_Error_TC | – | 08/01 | Octet sequence (9.3.3.1) | +| Function_Keys | SBV_DFK_TC | – | 14/01 | Octet sequence (9.3.3.3) | +| IB_Application_Address | BIS-N-CONNECT
SBV_Channel_Open_TC
SBV_Begin_Application_TC | 9 | – | (Note 1) | +| IB_Application_Data | BIS-N-CONNECT
SBV_Channel_Open_TC
SBV_Begin_Application_TC | 11 | – | Not defined in this Recommendation | +| IB_Application_Selection | BIS-N-CONNECT
SBV_Channel_Open_TC
SBV_Begin_Application_TC | 10 | – | Not defined in this Recommendation | +| IB_User_Data | BIS-N-CONNECT
SBV_Begin_Application_TC | | | (Note 2) | +| Ind_IB_Cause | SBV_Channel_Open_TC
SBV_Channel_Error_TC | – | 08/03 | Not defined in this Recommendation | +| Ind_IB_Diagnostic | SBV_Channel_Open_TC
SBV_Channel_Error_TC | – | 08/05 | Not defined in this Recommendation | +| Ind_OB_Cause | SBV_Channel_Open_TC
SBV_Channel_Error_TC | – | 08/11 | Not defined in this Recommendation | +| OB_Application_Address | BIS-N-CONNECT
SBV_Channel_Open_TC | – | 09/08 | (Note 1) | +| OB_Application_Data | BIS-N-CONNECT
SBV_Channel_Open_TC | – | 11/08 | Not defined in this Recommendation | +| OB_Application_Selection | BIS-N-CONNECT
SBV_Channel_Open_TC | – | 10/08 | Not defined in this Recommendation | +| OB_User_Data | BIS-N-CONNECT | | | (Note 2) | + +TABLE 46/T.105 (end) + +| Parameter | PDU(s) | Type
BCS | Type
ECS | Value or Remarks | +|--------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------|-------------|-------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| Packet_Size | SBV_Channel_Open_TC | – | 13/01 | Integer (Note 3)
7 ::= 128 octets
8 ::= 256 octets
9 ::= 512 octets
10 ::= 1024 octets
11 ::= 2048 octets | +| Window_Size | SBV_Channel_Open_TC | – | 13/02 | Integer (Note 3)
1..7 ::= Window size 1..7 | +| Reference | BIS-N-CONNECT
SBV_Channel_Open_TC
SBV_Channel_Close_TC
SBV_Channel_Error_TC | 12 | – | Not defined in this Recommendation | +| Req_IB_Called_Address | SBV_Channel_Open_TC | – | 08/04 | Not defined in this Recommendation | +| Req_IB_User_Data | SBV_Channel_Open_TC | – | 08/07 | Not defined in this Recommendation | +| Req_OB_Called_Address | SBV_Channel_Open_TC | – | 08/12 | Not defined in this Recommendation | +| Req_OB_Called_Subaddress | SBV_Channel_Open_TC | – | 08/13 | Not defined in this Recommendation | +| Req_OB_User_Data | SBV_Channel_Open_TC | – | 08/06 | Free format | +| Reset_Keys | SBV_DFK_TC | – | 14/02 | Void (9.3.3.3) | +| Result | BIS-N-CONNECT
BIS-N-DISCONNECT
SBV_Reset
SBV_Channel_Open_TC
SBV_Channel_Close_TC
SBV_Begin_Application_TC
SBV_TPD_Begin_TC | 13 | – | Integer
0 ::= “Successful”
1 ::= “Not successful”
2 ::= “Application not available”
3 ::= “Application already engaged”
4 ::= “Release not allowed”
5 ::= “TPD not supported”
6 ::= “Illegal Reference parameter” | +| Reverse_Role_Assignment | BIS-N-CONNECT | 14 | – | Void | +| Echo | SBV_Remote_Echo | – | 13/03 | Integer
0 ::= ON
1 ::= OFF | + +BCS Basic Coding Structure +ECS Extended Coding Structure + +## NOTES + +1 It is recommended to apply CCITT Recommendation X.121 [7]. + +2 To permit the distinction of a free-formatted parameter from parameters coded in accordance with 9.2, it is required to set the MSB of the first octet of the free-formatted parameter to 0. If used in conjunction with other parameters which are coded in accordance with 9.2, this parameter shall appear as the last one in the user data field. + +3 Other values are for further study. + +4 The Error\_Detection\_Location parameter is local only. Therefore, no value is given in this table. Nevertheless, value 08/02 shall be reserved with respect to future extensions, if any. + +### 9.3.2 Coding of user data fields as defined in other documents + +Table 47 shows parameters which are carried in the user data fields of the BIS-N-DATA and BIS-N-Q-DATA services. The coding of these parameters shall be performed according to the various Recommendations as defined in Table 47, without using the coding structure as defined in 9.2. + +The X.3 parameter manipulating services employ the parameter X.3\_Parameter\_List in accordance with CCITT Recommendation X.29 [6]. + +TABLE 47/T.105 + +| Parameter | BIS-Primitives | Recommendation | Remarks | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|---------| +| VTX_Data | BIS-N-DATA | Rec. T.101 [8] | Note 1 | +| TFI_Enq | BIS-N-Q-DATA | Rec. T.101 [8] | Note 2 | +| TFI_Ack | BIS-N-Q-DATA | Rec. T.101 [8] | Note 2 | +| X.3_Parameter_List | BIS-N-Q-DATA | 4.4.5/X.29 [6] | | +| NOTES
1 The VTX_Data parameter is directly mapped on the User data field of a DATA packet and coded in accordance with Recommendation T.101 [8]; it may therefore contain a TFI request (and response) in accordance with Recommendation T.101 [8]. If used in conjunction with the SBV_TPD services, this parameter may also carry processable data without making use of the DDU layer as specified in Recommendation T.101 [8].
2 These parameters are directly mapped onto the Telematic Command Message of the SBV_TFI_TC and coded in accordance with Recommendation T.101 [8]; the support of the particular Videotex presentation data element (VPDE) request is optional. | | | | + +### 9.3.3 Service specific coding + +#### 9.3.3.1 Coding of the Error\_Code parameter + +The Error\_Code parameter carried in the SBV\_TC\_Error TC is coded as a sequence of octets; the first octet (coded as an Integer) may take the value: + +- 00/00: “TC not supported” +- 00/01: “TC erroneous” +- 00/02: “unknown TC\_Event” +- 00/03: “TC semantic error” + +The first case (“TC not supported”) occurs either if the TC value (octet 3) contains a value which is not allowed (see 9.1) or if the value indicates an optional service which is not supported by the receiving side. + +NOTE – A given implementation will possibly not distinguish between a non-supported and an invalid TC code point. + +In the “TC not supported” case, the following octet shall contain the TC code of the received PDU which is not supported. + +EXAMPLE 1: This example (see Figure 9) shows the complete coding of the SBV\_TC\_Error TC for the case “TC not supported”. It is assumed that the SBV\_TPD\_Begin service is not implemented. + +| | | | +|---------|-------|---------------------------| +| Octet 1 | 04/00 | Telematic service message | +| Octet 2 | 09/14 | Syntax-based Videotex | +| Octet 3 | 00/01 | SBV_TC_Error_TC | +| Octet 4 | 00/05 | Length of TCM: 5 octets | +| Octet 5 | 15/15 | Extended coding structure | +| Octet 6 | 08/01 | Type: Error_Code | +| Octet 7 | 00/02 | Length: 2 octets | +| Octet 8 | 00/00 | Value: “TC not supported” | +| Octet 9 | 00/08 | Value: SBV_TPD_Begin | + +FIGURE 9/T.105 + +**Example 1 for the coding of the Error\_Code parameter** + +The second case (“TC erroneous”) occurs if the TC is supported, but the coding of one or several of the associated parameters is not correct. This case also occurs if a parameter is mandatory but missing. + +In the “TC erroneous” case, the following octets shall contain the TC code of the received TC indication, followed by a list of the erroneous or missing parameter(s). This list shall consist of octets containing the separate type indicator(s) of the erroneous parameter(s) involved. Type indicators which are defined for the Basic Coding Structure (see 9.2.1) shall be coded in the upper four bits of an octet, with the lower four bits set to 0. + +EXAMPLE 2: The following example (see Figure 10) shows the complete coding of the SBV\_TC\_Error TC for the case “TC erroneous”. It is assumed that the minimum set of the SBV\_DFK service (i.e. 8 keys) is implemented, but a previously received SBV\_DFK indication has tried to manipulate function key 10. + +| | | | +|----------|-------|---------------------------| +| Octet 1 | 04/00 | Telematic service message | +| Octet 2 | 09/14 | Syntax-based Videotex | +| Octet 3 | 00/01 | SBV_TC_Error_TC | +| Octet 4 | 00/06 | Length of TCM: 6 octets | +| Octet 5 | 15/15 | Extended coding structure | +| Octet 6 | 08/01 | Type: Error_Code | +| Octet 7 | 00/03 | Length: 3 octets | +| Octet 8 | 00/01 | Value: “TC erroneous” | +| Octet 9 | 00/10 | Value: SBV_DFK | +| Octet 10 | 14/01 | Value: Function_Keys | + +FIGURE 10/T.105 + +**Example 2 for the coding of the Error\_Code parameter** + +The third case (“Unknown TC\_Event”) occurs if within a received PDU either octet 2 or octet 4 or both are not in accordance with this Recommendation. + +In the “Unknown TC\_Event” case, the following octets shall contain octets 2, 3 and 4 of the received unknown TC\_event. + +EXAMPLE 3: The following example (see Figure 11) shows the complete coding of the SBV\_TC\_Error TC for the case “Unknown TC\_Event”. It is assumed that the recently received octet 2 was not correct. + +| | | | +|----------|-------|---------------------------| +| Octet 1 | 04/00 | Telematic service message | +| Octet 2 | 09/14 | Syntax-based Videotex | +| Octet 3 | 00/01 | SBV_TC_Error_TC | +| Octet 4 | 00/07 | Length of TCM: 7 octets | +| Octet 5 | 15/15 | Extended coding structure | +| Octet 6 | 08/01 | Type: Error_Code | +| Octet 7 | 00/04 | Length: 4 octets | +| Octet 8 | 00/02 | Value: “Unknown TC_Event” | +| Octet 9 | 00/00 | Value: Octet 2 | +| Octet 10 | 00/10 | Value: Octet 3 | +| Octet 11 | xx/yy | Value: Octet 4 | + +FIGURE 11/T.105 + +### Example 3 for the coding of the Error\_Code parameter + +The fourth case (“TC semantic error”) occurs if a received PDU belongs to a supported service but occurs at the wrong point in time, e.g. a well coded response which belongs to an other service than the one waiting for a response, or a response without a previous request, or a request instead of an expected response. + +In the “TC semantic error” case, the following octets shall contain the octet code of the receive PDU in the same manner as in case of “TC not supported”. + +### 9.3.3.2 Coding of the DDU\_Fall-Back\_Mode parameter + +The DDU\_Fall-Back\_Mode parameter is coded as a string. + +The possible characters in the string are restricted to: + +“A”, “B”, “C”, “D”, “E”, “F” and “G” (uppercase only). + +The string may contain one or several characters; the characters shall follow the alphabetic order; a character shall not be duplicated. + +EXAMPLE: Some possible valid values of the DDU\_Fall-Back\_Mode parameter: + +- “B”; +- “ABDEG”; +- “ABCDEFGG”. + +### 9.3.3.3 Coding of the Function\_Keys parameter + +The SBV\_DFK TC Function\_Keys parameter is a structured data type. It carries a list of function key definitions. Each function key consists of an identification, an optional user visible name, an optional code sequence and an optional “do-not-forward” indication. + +Table 48 defines the coding of the type indicators. + +TABLE 48/T.105 + +| Type indicator | Data element | +|----------------|-------------------| +| 06/00 | Function Key | +| 06/01 | Identification | +| 06/02 | User Visible Name | +| 06/03 | Code Sequence | +| 06/04 | Do-not-forward | + +The user visible name may be used by the Terminal Function to inform the user about the purpose of a function key. The code sequence is a sequence of octets which has to be sent to the Access Function when the function key is depressed. By default, the function key shall be associated with a forwarding condition. The presence of a do-not-forward indication defines that the function key shall not be associated with a forwarding condition. + +The Terminal Function shall process the conditions in the received order. When setting a specific function key twice in one Telematic Command, the value of the last received definition shall be used. Reset commands which are sent in between function key lists shall be processed. + +The list of function keys is coded as a structure. Each element of this structure is coded in a TLV (type-length-value) form, which conforms to the extended coding structure as defined in 9.2.2. + +The identification is coded as an integer. For terminals supporting the SBV\_DFK service, at least values 1 to 8 shall be supported. The user visible name shall be encoded as a string of the indicated length. The code sequence shall be encoded as a sequence of octets of the indicated length. The values of these octets are not limited to a specific data syntax. The do-not-forward indication shall be encoded as a void type. + +The following formal specification gives the syntax of the Function\_Keys data-structure: + +``` + +Function_Keys ::= "15/15" "14/01" Length Function_Key_List +Function_Key_List ::= Function_Key Function_Key_List + | /* empty */ +Function_Key ::= "06/00" Length Identification + User_visible_name + Code_sequence + Do_not_forward + +Identification ::= "06/01" Length Integer +User_visible_name ::= "06/02" Length String + | /* empty */ +Code_sequence ::= "06/03" Length Octet_sequence + | /* empty */ +Do_not_forward ::= "06/04" "00/00" + | /* empty */ + +Length ::= "Octet conforming to the length type in 9.2.2" +Integer ::= "Integer conforming to 9.2.3.1" +String ::= "String conforming to 9.2.3.2" +Octet_sequence ::= "Octet sequence conforming to 9.2.3.4" + +``` + +The following examples illustrate the use of the SBV\_DFK service, showing the complete coding for the SBV\_DFK TC: + +EXAMPLE 1: After deleting all current definitions, associate key 1 with the user visible name “F1” and the code string “Code1”, and key 10 with the user visible name “F10” and the code sequence “Code2” (see Figure 12). + +| | | | +|-------|---------------------------|-------------------| +| 04/00 | Telematic service message | | +| 09/14 | Syntax-based Videotex | | +| 00/10 | SBV_DFK_TC | | +| 02/07 | Length of TCM: 39 octets | | +| 15/15 | Extended coding structure | | +| 14/02 | Reset | | +| 00/00 | length = 0 | | +| 15/15 | Extended coding structure | | +| 14/01 | function key list | | +| 02/01 | length = 33 | | +| 06/00 | function key | | +| 00/14 | length = 14 | | +| | 06/01 | identification | +| | 00/01 | length = 1 | +| | 00/01 | value = 1 | +| | 06/02 | user visible name | +| | 00/02 | length = 2 | +| | “F” | value = “F1” | +| | “1” | | +| | 06/03 | code sequence | +| | 00/05 | length = 5 | +| | “C” | value = “Code1” | +| | “o” | | +| | “d” | | +| | “e” | | +| | “1” | | +| 06/00 | function key | | +| 00/15 | length = 15 | | +| | 06/01 | identification | +| | 00/01 | length = 1 | +| | 00/10 | value = 10 | +| | 06/02 | user visible name | +| | 00/03 | length = 3 | +| | “F” | value = “F10” | +| | “1” | | +| | “0” | | +| | 06/03 | code sequence | +| | 00/05 | length = 5 | +| | “C” | value = “Code2” | +| | “o” | | +| | “d” | | +| | “e” | | +| | “2” | | + +FIGURE 12/T.105 + +**Example 1 for the coding of the SBV\_DFK TC PDU** + +EXAMPLE 2: Erase reset key 10 and overwrite key 1 with “FN” for the user visible name and code string “New”, which is not a forwarding condition (see Figure 13). + +| | | | +|-------|---------------------------|--| +| 04/00 | Telematic service message | | +| 09/14 | Syntax-based Videotex | | +| 00/10 | SBV_DFK_TC | | +| 01/08 | Length of TCM: 24 octets | | +| 15/15 | Extended coding structure | | +| 14/01 | function key list | | +| 01/05 | length = 21 | | +| 06/00 | function key | | +| 00/03 | length = 14 | | +| 06/01 | identification | | +| 00/01 | length = 1 | | +| 00/10 | value = 10 | | +| 06/00 | function key | | +| 00/14 | length = 14 | | +| 06/01 | identification | | +| 00/01 | length = 1 | | +| 00/01 | value = 1 | | +| 06/02 | user visible name | | +| 00/02 | length = 2 | | +| “F” | value = “FN” | | +| “N” | | | +| 06/03 | code sequence | | +| 00/03 | length = 3 | | +| “N” | value = “New” | | +| “e” | | | +| “w” | | | +| 06/04 | Do not_forward | | +| 00/00 | length = 0 | | + +FIGURE 13/T.105 + +#### Example 2 for the coding of the SBV\_DFK TC PDU + +## 10 Use of CCITT Recommendation X.3 parameters + +CCITT Recommendation X.3 [3] parameters shall be used as described in the relevant CCITT Recommendations. Additional rules are given in this Recommendation. The values of the X.3 parameters given in this Recommendation shall be changed only through the use of the SBV\_Set\_Param, SBV\_Set\_Read\_Param, and SBV\_Reset services. The values shall not be changed by the Terminal Function itself. + +### 10.1 Selectable functions provided by Syntax-based Videotex Terminals + +For a global description of these functions, refer to the Terminal Model described in 6.2. + +## 10.2 List of X.3 parameters + +For the description of the X.3 parameters refer to CCITT Recommendation X.3 [3], 1.4. The following parameters are selected (see Table 49) for the Syntax-based Videotex Terminal Function. + +TABLE 49/T.105 + +**Supported CCITT Recommendation X.3 [3] parameters** + +| Parameter reference number | Parameter description | +|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------| +| 2 (M) | Echo | +| 3 (M) | Selection of data forwarding characters (Note 1) | +| 4 (M) | Selection of idle timer delay (Note 2) | +| 11 (M) | Binary speed (Note 3) | +| 23 (O) | Size of input field | +| 24 (O) | End of frame | +| 25 (O) | Selection of extended data forwarding signals | +| 26 (O) | Display interrupt | +| 28 (O) | Diacritic character editing | +| 29 (O) | Extended echo mask | +|
M Mandatory
O Optional
NOTES
1 In addition to CCITT Recommendation X.3 [3], the values 1 and 16 are mandatory values in this Recommendation.
2 In addition to CCITT Recommendation X.3 [3], the parameter value 1 is mandatory in this Recommendation. Some Syntax-based Videotex Terminals may interpret this value in the sense of “as soon as possible”.
3 This Parameter shall be used to indicate the binary speed between the TF and the AF. This is based on parameter reference 11 as defined in CCITT Recommendation X.3 [3]. Possible values can be given by a Recommendation related to the lower layers.
| | + +## 11 Bearer Independent Service (BIS) for Syntax-based Videotex + +### 11.1 Introduction + +The upper layers In-Band protocol of Syntax-based Videotex (higher than 3) makes use of CCITT Recommendation X.29 [6] based procedures. In some cases, additional procedures, e.g. to establish a physical link or e.g. to handle the access to the network are used, named Out-Band procedures. + +The purpose of this clause is to define a Bearer Independent Service for the application of Syntax-based Videotex, named BIS. + +The In-Band procedures used to support the BIS are defined by this clause. + +The Out-Band procedures depend strongly on the network type, the method to establish a physical link or to access the network. They cannot be given entirely here. Subclause 11.3.1 provides for an anchorage to be used by other documents being specific to a certain network type. + +NOTE – All physical layer aspects are assumed to be given by those documents as well. + +## 11.2 Scope and field of application + +The BIS is defined for the specific application of Syntax-based Videotex as service user, but other applications are not excluded. + +The principal objectives of the BIS definition are: + +- a) to specify the characteristics of a conceptual Network Service, hiding from the Network Service user how the service is provided; +- b) to realize the service through the use of X.25/PLP, and some Out-Band protocol if appropriate. + +The BIS is defined in terms of: + +- 1) the service primitives and their associated parameters; +- 2) X.25 packets and fields; +- 3) the interrelationship between, and the valid sequences of, these primitives and packets. + +NOTE 1 – The use of Out-Band specific protocol elements is assumed to be determined by documents related to the Out-Band procedures. + +Apart from the In-Band/Out-Band coordination and the qualified data transfer service (data with Q-bit = 1), the functions and procedures defined in this clause are a subset of the OSI Connection-mode Network Service. Quality of service functions, although out of the scope of this Bearer Independent Service, are not precluded. + +For the In-Band protocol, ISO/IEC 8208 [15] or CCITT Recommendation X.25 (1980) [4] or later versions of Recommendation X.25 shall be used with the following rules: + +NOTE 2 – The option of using some facilities may only be employed if the version is either ISO/IEC 8208 [15] or CCITT Recommendation X.25 (1984) [5] or later. + +- Only the X.25 Virtual Call service applies to the BIS. The use of X.25 Permanent Virtual Circuit service for the purposes of the BIS is excluded. +- The BIS is provided within a DTE (in X.25 terminology), by the use of X.25 procedures across a DTE/DCE or a DTE/DTE interface as well. + +NOTE 3 – The physical layer aspects for the In-Band procedures will depend strongly on the network type. They are assumed to be determined by documents related to the Out-Band procedures. + +In particular, the BIS provides for the following: + +- a) *Independence of underlying transmission media* + +The BIS relieves BIS users of all concerns regarding how various sub-networks are used to provide the BIS or the access to them. The BIS hides from the BIS user differences in the transfer of data over heterogeneous sub-networks. +- b) *End-to-end transfer* + +The BIS provides for transfer of BIS user data between BIS users in **end systems**. All routing and relaying functions are performed by the BIS provider. +- c) *Transparency of transferred information* + +The BIS provides for the transparent transfer of octet-aligned BIS user data. It does not restrict the contents, format or coding of the information, nor does it ever need to interpret its structure or meaning. + +The BIS offers the following features to an BIS user: + +- 1) The means to establish a Network Connection (NC) with another BIS user for the purpose of transferring BIS user data by means of data transfer primitives. More than one NC may exist between the same pair of BIS users. +- 2) The means of transferring BIS user data in so-called BIS Data Units (BIS-DUs) in sequence on a NC. The transfer of BIS-DUs, which consist of an integer number of octets, is transparent, in that the boundaries of BIS-DUs and the contents of BIS-DUs are preserved unchanged by the BIS, and there are no constraints on the BIS-DU content imposed by the BIS. Two different types of user data transfer services are provided: + - the “unqualified” data transfer service; + - the “qualified” data transfer service. + +- 3) The means of transferring expedited data in so-called BIS-Interrupt BIS-DUs, which consist of an integer number of octets, is transparent, in that the boundaries of BIS-DUs and the contents of BIS-DUs are preserved unchanged by this BIS, and there are no constraints on the BIS-DU content imposed by the BIS. +- 4) The means by which the NC can be returned to a definite state and activities of the two BIS users synchronized by use of a reset service. +- 5) The unconditional, and therefore possibly destructive, release of an NC by either of the BIS users or by the BIS provider. + +The BIS does not specify individual implementations or products nor does it constrain the implementation of entities and interfaces within a computer system. In other words, BIS defines an Abstract Service interface; the internal representation of its Abstract Service Primitives is a local matter. + +## 11.3 General operation of the BIS + +### 11.3.1 Out-Band Procedures for Environment-dependent operation + +The X.25/PLP is used to provide the BIS in an end system connected directly to an X.25 packet-switched network (dedicated access), or it can be used in environments, where an intermediate access path has to be provided either between the endsystem and the X.25 packet-switched network or between the two end systems (e.g. through an ISDN). + +The establishment of a physical link or an intermediate access path, if necessary, is performed by a sub-function of the NL normally called coordination function. The description of the operation of the coordination function depends on the environment and is outside the scope of this Recommendation. + +It is assumed however, that, before the procedures of the BIS defined in the subclauses below apply, the following steps are taken, when a BIS-N-CONNECT request is received by the NL entity: + +- a) The physical access path shall be established by the NL entity if necessary. Possible retries after a first failure are a local matter. After successful establishment, the initialization defined in b) and c) below, shall be performed. +- b) A Data Link Connection shall be initiated by the NL entity if it does not already exist. +- c) The X.25/PLP RESTART procedure shall be initiated by the NL entity, if the Data Link Connection was established in step b). + +It is not within the scope of this Recommendation to indicate how the NL entity is informed of the outcome of the procedures a), b) and c), but it is assumed that the NL entity is informed of the outcome. If the outcome is positive, the procedures of the BIS defined in the subclauses below apply. If the outcome is negative, a BIS-N-DISCONNECT indication is issued to the BIS user. + +It is not within the scope of this Recommendation whether an existing access path is used for the establishment of a new Virtual Call supporting a BIS-N-CONNECT request (using, e.g. more than one LC), or whether a new access path has to be established. + +It is assumed that the SBV\_Establish address parameters the names of which start with "OB\_" form part of the BISAP address and are used to establish the access path. Furthermore, it is assumed that the contents of the other SBV\_Establish parameters the names of which start with "OB\_" are conveyed by some Out-Band data transfer means (e.g. UUS in case of ISDN), if available, before the In-Band procedures take place. + +In a similar way as above for the BIS-N-CONNECT request primitive, it is assumed, that the initialization procedures in a), b) and c) have been completed before an BIS-N-CONNECT indication can be signalled to the BIS user. + +It is further assumed, that in case the environment in which the X.25/PLP operates prematurely breaks down (i.e. while one or more NCs are established or in the process of being established), then the NL entity signals for each established NC and for each NC in the process of being established, a BIS-N-DISCONNECT indication to the BIS user. + +The particular values of the Originator and Reason parameters passed to the BIS user in case of an unsuccessful path establishment or a premature breakdown of the access path are outside the scope of this Recommendation. However, the following rules shall be obeyed: + +- 1) If an access network connection or a VC cannot be established for local reasons (e.g. no B-channel available if the access network is an ISDN, or if no LC is available), the “originator” value shall be “local” and no “reason” value is specified. + +- 2) If the access network connection establishment cannot be completed, or there is a premature breakdown of the access path, the “originator” value shall be according to the access network the end system is connected to (e.g. “ISDN” if the access network is an ISDN). The “reason” value depends on the access network. + +**11.3.2 Translation of primitives and parameters of In-Band Procedures** + +As shown in Figure 14, the BIS provider (more particularly, the NL entity in the end system) must provide a translation between: + +- the primitives and parameters of the BIS; and + +- the packets and associated fields of the X.25/PLP. + +![Figure 14/T.105 - Operation of the BIS](4464bc13e0077cb62ad54bf6c7473755_img.jpg) + +The diagram illustrates the operation of the BIS between two end systems, End System A and End System B. Each end system contains a BIS User and an NL Entity. The BIS User and NL Entity are separated by a horizontal dashed line representing the Bearer Independent Service boundary. BIS Primitives are exchanged across this boundary. Below the boundary, the NL Entities of both systems communicate via X.25 PLP packets across a DTE/DXE Interface, represented by a central dashed line. Arrows indicate the flow of primitives between BIS User and NL Entity, and the flow of X.25 PLP packets between the NL Entities of the two systems. + +Figure 14/T.105 - Operation of the BIS + +NOTE – Out-Band related matters are not shown here. + +FIGURE 14/T.105 +**Operation of the BIS** + +Request and response primitives are translated into packets (where appropriate) to be transmitted across the DTE/DXE interface by the NL entity. Received packets, where appropriate are translated by the NL entity into indication and confirm primitives. + +54 Recommendation T.105 (11/94) + +There is also a relationship between some local mechanism used to identify a particular NC and a LC number used to identify a particular virtual circuit. This relationship is a local matter and not subject to standardization. + +NOTE – There may be X.25/PLP compatible functions implemented in an end system which are outside the scope of this Recommendation, but which may have an effect on the provision of the BIS, e.g. if an end system chooses to consider QOS aspects and a certain QOS cannot be achieved for a particular VC, a BIS-N-CONNECT request may be refused. + +## 11.4 Service primitives and parameters + +The following subclauses define the service primitives applicable to the various phases occurring during the provision of the BIS on a particular NC, and the parameters associated to them. + +The mapping given in this subclause shall be used when the mapping is In-Band caused. The Out-Band caused mapping is not defined by this Recommendation. + +NOTE – It is assumed that the Out-Band caused mapping is covered by documents being specific to a certain network (see 11.3.1). + +Sometimes, the availability of a parameter for a service primitive depends on the support of the Fast Select facility for the NC. The knowledge whether Fast Select is supported, is a local matter and not indicated by a parameter of the BIS. + +### 11.4.1 NC establishment primitives and parameters + +NC establishment may have Out-Band related aspects (see 11.3.1) which are not defined here. The rules defined in this subclause shall be respected for all In-Band related aspects of the NC establishment. + +#### 11.4.1.1 Association of primitives and parameters + +Table 50 shows the service primitives applicable in the NC establishment phase and the parameters associated to them. + +TABLE 50/T.105 + +**NC Establishment primitives and parameters** + +| Parameters | BIS-N-CONNECT
request | BIS-N-CONNECT
indication | BIS-N-CONNECT
response | BIS-N-CONNECT
confirm | +|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------|-----------------------------|---------------------------|--------------------------| +| Called Address | X | X (=) | | | +| Calling Address | X | X (=) | | | +| Responding Address | | | X | X (=) | +| BIS-user-data | X | X (=) | X | X (C=) | +| (=) The parameter value supplied in an indication or confirm primitive is identical to the value supplied in the corresponding request or response primitive occurring at the peer BISAP.
(C) The parameter is not present on the primitive for every NC; the parameter definition describes the conditions under which the parameter is present or absent. | | | | | + +#### 11.4.1.2 Parameter definitions + +- **Called Address** – The Called Address parameter contains one or more addresses, used to identify the BISAP to which the NC is to be established. +- **Calling Address** – The Calling Address parameter contains one or more addresses, used to identify the BISAP from which the NC is requested. +- **Responding Address** – The Responding Address parameter contains one or more addresses, used to identify the BISAP to which the NC has been established. + +## NOTES + +- 1 Addresses may be implicitly associated with the BISAP at which the primitive is used. + - 2 Depending on the environment (see 11.3.1) more than one address may be necessary to identify a BISAP. As a consequence, the abstract Called Address parameter may comprise more than one physical part, mapped onto more than one underlying protocol element field + - 3 Mechanisms operating within the BIS provider, e.g. call redirection, may result in address parameters in corresponding primitives not being identical in the following cases: + - a) the responding address parameter in the BIS-N-CONNECT response may not necessarily be the same as the called address parameter in the BIS-N-CONNECT indication; + - b) the responding address parameter in the BIS-N-CONNECT confirm may not necessarily be the same as the called address parameter in the BIS-N-CONNECT request. +- **BIS-user-data** – The BIS-user-data parameter is used to transfer BIS user data (an integer number of octets) between BIS users, without modification by the BIS provider. + +NOTE – The BIS-user-data abstract parameter may comprise more than one physical part, mapped onto more than one underlying protocol element field, depending on the environment. For instance, in case of an ISDN, some part may be mapped onto the UUI part of a SETUP message, an other part may be mapped onto the Call User Data field of an X.25 CALL REQUEST. The BIS-user-data abstract parameter is not necessarily a continuous block of data. + +The BIS-user-data parameter information that makes use of the X.25/PLP Fast Select facility (see 11.5.3) is subject to the following rule: for a BIS-N-CONNECT request or indication, the allowed parameter length is between 0 and 128 octets when Fast Select is used, otherwise the allowed length is between 0 and 16 octets. + +The BIS-user-data parameter is optional for the BIS-N-CONNECT response and confirm; in these cases it may only be used, if the Fast Select Acceptance facility is supported and the Fast Select facility is used for the NC. + +### 11.4.2 NC release primitives and parameters + +NC release may have Out-Band related aspects (see 11.3.1) which are not defined here. The rules defined in this subclause shall be respected for all In-Band related aspects of the NC release. + +#### 11.4.2.1 Association of primitives and parameters + +Table 51 shows the service primitives applicable in the NC release phase and the parameters associated to them. + +TABLE 51/T.105 + +#### NC Release primitives and parameters + +| Parameters | BIS-N-DISCONNECT
request | BIS-N-DISCONNECT
indication | +|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------|--------------------------------| +| Originator | X | X | +| Reason | X | X | +| Responding Address | X (C) | X (C=) | +| BIS-user-data | X (C) | X (C=) | +| (=) The parameter value supplied in an indication primitive is identical to the value supplied in the corresponding request primitive occurring at the peer BISAP.
(C) The parameter is not present on the primitive for every NC; the parameter definition describes the conditions under which the parameter is present or absent. | | | + +### 11.4.2.2 Parameter definitions + +- **Originator** – The Originator parameter indicates the source of the NC release. Its value shall be an X.25 cause. + +NOTE – For not In-Band caused NC releases, the Originator parameter may also take other values like “local” or Out-Band related values like “PSTN” or “ISDN”. + +- **Reason** – The Reason parameter gives information about the cause of the NC release. The value conveyed in this parameter shall be an X.25 diagnostic. + +#### NOTES + +1 For not In-Band caused NC releases, the Reason parameter may also take other values like “unspecified” or Out-Band related values like a Q.931 cause in case of an ISDN. + +2 Further information on the value to be selected for the originator and reason parameters in case of an In-Band caused NC release can be found in 11.7 “Network connection release phase”. + +- **Responding Address** – The Responding Address parameter is an optional parameter which may only be used, if the Fast Select facility is supported for the NC. Furthermore, it is only present in case the primitive is used to indicate rejection of an NC establishment attempt by a BIS user. In this case it contains one or more addresses, used to identify the BISAP from which the BIS-N-DISCONNECT request was issued. + +#### NOTES + +1 Addresses may be implicitly associated with the BISAP at which the primitive is used. + +2 Depending on sub-networks between BIS users, e.g. PSTNs or ISDNs, more than one address may be necessary to identify a BISAP. The contents of the address parameter is outside the scope of this Recommendation. + +- **BIS-user-data** – The BIS-user-data parameter is used to transfer BIS user data (an integer number of octets) between BIS users, without modification by the BIS provider. The parameter is optional and may only be used, if the Fast Select facility is used for the NC. + +If the Fast Select facility is used for the NC, the maximum parameter length is 128 octets for each primitive. + +The BIS-user-data sent is lost if NC release is simultaneously invoked by either the BIS provider or the intended receiving BIS user. + +### 11.4.3 Unqualified data transfer primitives and parameters + +Unqualified data transfer has no Out-Band related aspects. + +#### 11.4.3.1 Association of primitives and parameters + +Table 52 shows the service primitives applicable to the transfer of unqualified data in the data transfer phase, and the parameters associated to them. + +TABLE 52/T.105 + +#### Data Transfer (unqualified) primitives and parameters + +| Parameters | BIS-N-DATA request | BIS-N-DATA indication | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------|-----------------------| +| BIS-user-data | X | X (=) | +| (=) The parameter value supplied in an indication primitive is identical to the value supplied in the corresponding request primitive occurring at the peer BISAP. | | | + +### 11.4.3.2 Parameter definitions + +- **BIS-user-data** – The BIS-user-data parameter is used to transfer BIS user data (one or more octets) between BIS users, without modification by the BIS provider. + +### 11.4.4 Qualified data transfer primitives and parameters + +Qualified data transfer has no Out-Band related aspects. + +#### 11.4.4.1 Association of primitives and parameters + +Table 53 shows the service primitives applicable to the transfer of qualified data in the data transfer phase, and the parameters associated to them. + +TABLE 53/T.105 + +#### Qualified data transfer primitives and parameters + +| Parameters | BIS-N-Q-DATA request | BIS-N-Q-DATA indication | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------|-------------------------| +| BIS-user-data | X | X (=) | +| (=) The parameter value supplied in an indication primitive is identical to the value supplied in the corresponding request primitive occurring at the peer BISAP. | | | + +### 11.4.4.2 Parameter definitions + +- **BIS-user-data** – The BIS-user-data parameter is used to transfer qualified BIS user data (one or more octets) between BIS users, without modification by the BIS provider. + +### 11.4.5 Interrupt data transfer primitives and parameters + +Interrupt data transfer has no Out-Band related aspects. + +#### 11.4.5.1 Association of primitives and parameters + +Table 54 shows the service primitives applicable to the transfer of interrupt data in the data transfer phase, and the parameters associated to them. + +TABLE 54/T.105 + +#### Interrupt data transfer primitives and parameters + +| Parameters | BIS-N-INTERRUPT request | BIS-N-INTERRUPT ndication | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------|---------------------------| +| BIS-interrupt-user-data | X | X (=) | +| (=) The parameter value supplied in an indication primitive is identical to the value supplied in the corresponding request primitive occurring at the peer BISAP. | | | + +### 11.4.5.2 Parameter definitions + +- **BIS-interrupt-user-data** – the BIS-interrupt-user-data parameter is used to transfer interrupt BIS user data (one or more octets) between BIS users, without modification by the BIS provider. + +## 11.4.6 Reset primitives and parameters + +BIS reset has no Out-Band related aspects. + +### 11.4.6.1 Association of primitives and parameters + +Table 55 shows the service primitives applicable to the reset service in the data transfer phase, and the parameters associated to them. + +TABLE 55/T.105 + +**Reset primitives and parameters** + +| Parameters | BIS-N-RESET
request | BIS-N-RESET
indication | BIS-N-RESET
response | BIS-N-RESET
confirm | +|------------|------------------------|---------------------------|-------------------------|------------------------| +| Originator | X | X | – | – | +| Reason | X | X | – | – | + +### 11.4.6.2 Parameter definitions + +- **Originator** – The Originator parameter indicates the source of the NC reset. Its value is directly mapped to/from the X.25 cause of the related RESET REQUEST/INDICATION packet. +- **Reason** – The Reason parameter gives information indicating the cause of the NC reset. Its value is directly mapped to/from the X.25 diagnostics of the related RESET REQUEST/INDICATION packet. + +Further information on the values to be selected for the originator and reason parameter can be found in 11.10.2.3, “Originator and Reason”. + +### 11.4.7 Relation of primitives at the two NC endpoints + +A primitive issued at one NC endpoint will, in general, have consequences at the other NC endpoint. The relations of primitives of each type to primitives at the other NC endpoint are summarized in Figure 15. + +### 11.4.8 Sequence of primitives at one NC endpoint + +The valid overall sequences of primitives at an NC endpoint are defined in the state transition diagrams of Figure 16. In the diagrams: + +- A primitive which is not shown as resulting in a transition (from one state to the same state or from one state to a different state), is not permitted in that state. The actions to be performed in this case are a local matter and not subject to standardization. +- The labelling of the states “BIS user invoked reset pending” (state 5) and “BIS provider invoked reset pending” (state 6) indicates the party which started the local interaction, and does not necessarily reflect the value of the “originator” parameter in the associated BIS-N-RESET primitive. +- The Idle (state 1) reflects the absence of an NC. It is the initial and final state of any sequence, and once it has been re-entered, the NC is released. +- The use of a state transition diagram to describe the allowable sequences of service primitives does not impose any requirements or constraints on the internal organization of any implementation of the BIS. + +Figure 16 shows for each state the permitted service primitives to be issued, and the state to be entered afterwards. + +![Summary of BIS service primitive time sequence diagrams showing 14 scenarios (a-n) for NC establishment, release, data transfer, and reset.](15de63f0b5df62e6ab9164f2a72e2e33_img.jpg) + +The diagram illustrates 14 scenarios (a-n) for BIS service primitive time sequence diagrams, showing the interaction between a BIS user and a BIS provider. + +- a) Successful NC establishment:** BIS-N-CONNECT request (user to provider) and BIS-N-CONNECT confirm (provider to user) on the user side; BIS-N-CONNECT indication (provider to user) and BIS-N-CONNECT response (user to provider) on the provider side. +- b) BIS user invoked NC release:** BIS-N-DISCONNECT request (user to provider) and BIS-N-DISCONNECT indication (provider to user) on the provider side. +- c) Simultaneous user invoked NC release:** BIS-N-DISCONNECT request (user to provider) and BIS-N-DISCONNECT request (provider to user) on the provider side. +- d) BIS provider invoked NC release:** BIS-N-DISCONNECT indication (provider to user) and BIS-N-DISCONNECT indication (user to provider) on the provider side. +- e) Simultaneous BIS user and BIS provider invoked NC release:** BIS-N-DISCONNECT request (user to provider) and BIS-N-DISCONNECT indication (provider to user) on the provider side. +- f) BIS user rejection of an NC establishment attempt:** BIS-N-CONNECT request (user to provider) and BIS-N-CONNECT indication (provider to user) on the provider side; BIS-N-DISCONNECT request (provider to user) and BIS-N-DISCONNECT indication (user to provider) on the provider side. +- g) BIS provider rejection of an NC establishment attempt:** BIS-N-CONNECT request (user to provider) and BIS-N-DISCONNECT indication (provider to user) on the provider side. +- h) Normal data transfer:** BIS-N-DATA request (user to provider) and BIS-N-DATA indication (provider to user) on the provider side. +- i) Qualified data transfer:** BIS-N-DATA request (user to provider) and BIS-N-Q-DATA indication (provider to user) on the provider side. +- j) BIS user invoked reset:** BIS-N-RESET request (user to provider) and BIS-N-RESET confirm (provider to user) on the user side; BIS-N-RESET indication (provider to user) and BIS-N-RESET response (user to provider) on the provider side. +- k) Simultaneous user invoked reset:** BIS-N-RESET request (user to provider) and BIS-N-RESET request (provider to user) on the provider side; BIS-N-RESET confirm (provider to user) and BIS-N-RESET confirm (user to provider) on the provider side. +- l) BIS provider invoked reset:** BIS-N-RESET indication (provider to user) and BIS-N-RESET response (user to provider) on the provider side; BIS-N-RESET indication (user to provider) and BIS-N-RESET response (provider to user) on the provider side. +- m) Simultaneous BIS user and BIS provider invoked reset:** BIS-N-RESET request (user to provider) and BIS-N-RESET indication (provider to user) on the provider side; BIS-N-RESET confirm (provider to user) and BIS-N-RESET response (user to provider) on the provider side. +- n) Interrupt data transfer:** BIS-N-INTERRUPT request (user to provider) and BIS-N-INTERRUPT indication (provider to user) on the provider side. + +Summary of BIS service primitive time sequence diagrams showing 14 scenarios (a-n) for NC establishment, release, data transfer, and reset. + +T0815180-94/d05 + +NOTE – See 11.10.2.2 for the relation between BIS-N-RESET confirm and response + +FIGURE 15/T.105 +Summary of BIS service primitive time sequence diagrams + +![State transition diagram for BIS-N states. It shows transitions between Idle (state 1), Outgoing connection pending (state 2), Incoming connection pending (state 3), Data transfer ready (state 4), BIS user invoked reset pending (state 5), and BIS provider invoked reset pending (state 6).](af6c3f383ddc0c142cdd7e186cc78199_img.jpg) + +``` + +stateDiagram-v2 + state "Idle (state 1)" as S1 + state "Outgoing connection pending (state 2)" as S2 + state "Incoming connection pending (state 3)" as S3 + state "Data transfer ready (state 4)" as S4 + state "BIS user invoked reset pending (state 5)" as S5 + state "BIS provider invoked reset pending (state 6)" as S6 + + S1 --> S2 : BIS-N-CONNECT request + S1 --> S3 : BIS-N-CONNECT Indication + S2 --> S1 : BIS-N-DISCONNECT request/indication + S2 --> S4 : BIS-N-CONNECT confirm + S3 --> S1 : BIS-N-DISCONNECT request/indication + S3 --> S4 : BIS-N-CONNECT response + S4 --> S1 : BIS-N-DISCONNECT request/indication + S4 --> S5 : BIS-N-RESET request + S4 --> S6 : BIS-N-RESET Indication + S4 --> S4 : BIS-N-DATA request/indication + S4 --> S4 : BIS-N-Q-DATA request/indication + S4 --> S4 : BIS-N-INTERRUPT request/indication + S5 --> S1 : BIS-N-DISCONNECT request/indication + S5 --> S4 : BIS-N-RESET confirm + S6 --> S1 : BIS-N-DISCONNECT request/indication + S6 --> S4 : BIS-N-RESET response + +``` + +The diagram illustrates the state transitions for the BIS-N protocol. It consists of six states and the transitions between them triggered by specific events. + +- Idle (state 1)** transitions to **Outgoing connection pending (state 2)** on a **BIS-N-CONNECT request** and to **Incoming connection pending (state 3)** on a **BIS-N-CONNECT Indication**. +- Outgoing connection pending (state 2)** transitions back to **Idle (state 1)** on a **BIS-N-DISCONNECT request/indication** and to **Data transfer ready (state 4)** on a **BIS-N-CONNECT confirm**. +- Incoming connection pending (state 3)** transitions back to **Idle (state 1)** on a **BIS-N-DISCONNECT request/indication** and to **Data transfer ready (state 4)** on a **BIS-N-CONNECT response**. +- Data transfer ready (state 4)** is a central state with multiple outgoing transitions: + - Back to **Idle (state 1)** on a **BIS-N-DISCONNECT request/indication**. + - To **BIS user invoked reset pending (state 5)** on a **BIS-N-RESET request**. + - To **BIS provider invoked reset pending (state 6)** on a **BIS-N-RESET Indication**. + - Remains in **Data transfer ready (state 4)** on **BIS-N-DATA request/indication**, **BIS-N-Q-DATA request/indication**, and **BIS-N-INTERRUPT request/indication**. +- BIS user invoked reset pending (state 5)** transitions back to **Idle (state 1)** on a **BIS-N-DISCONNECT request/indication** and to **Data transfer ready (state 4)** on a **BIS-N-RESET confirm**. +- BIS provider invoked reset pending (state 6)** transitions back to **Idle (state 1)** on a **BIS-N-DISCONNECT request/indication** and to **Data transfer ready (state 4)** on a **BIS-N-RESET response**. + +State transition diagram for BIS-N states. It shows transitions between Idle (state 1), Outgoing connection pending (state 2), Incoming connection pending (state 3), Data transfer ready (state 4), BIS user invoked reset pending (state 5), and BIS provider invoked reset pending (state 6). + +FIGURE 16/T.105 +state transition diagram + +T0815190-94/d06 + +## 11.5 Elements of the X.25/PLP used to support the BIS + +The X.25/PLP, as defined by ISO/IEC 8208 [15], provides the realization for the transparent transfer of qualified and unqualified data between BIS users. The elements of this protocol to be considered here are: + +- a) virtual circuits; +- b) the packet types and fields to be mapped to the primitives and parameters of the BIS; +- c) optional user facilities and CCITT-specified DTE facilities. + +No facilities are mandatory for the operation of the BIS, some facilities are indicated as an option, and no facility except “Fast Select with restriction on response” is excluded. + +### 11.5.1 Types of virtual circuits + +Of the two types of virtual circuits defined in ISO/IEC 8208 [15], only the use of Virtual Calls is mapped to the NC establishment and release phases of the BIS (see 11.6 and 11.7). + +NOTE – A corresponding mapping for permanent virtual circuits is not defined. + +### 11.5.2 Packets and fields of the X.25/PLP used to support the BIS + +Table 56 below lists the X.25/PLP packets and associated fields that shall be used when supporting the BIS. + +TABLE 56/T.105 + +#### X.25 packets and fields to support the BIS + +| Packets (Note 1) | Fields (Note 2) | +|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------| +| CALL REQUEST
INCOMING CALL
CALL ACCEPTED
CALL CONNECTED | Address field
Facility field
Calling/Called User Data field (Note 3) | +| CLEAR REQUEST
CLEAR INDICATION | Clearing Cause field
Diagnostic Code field
Address field
Facility field (Note 4)
Clear User Data field (Note 3) | +| DATA | Q-bit
M-bit
User Data field (Note 3) | +| INTERRUPT
RESET REQUEST
RESET INDICATION | Interrupt User Data field (Note 3)
Resetting Cause field
Diagnostic Code field | +| RESTART REQUEST
RESTART INDICATION | Restarting Cause field
Diagnostic Code field | +|

NOTES

1 The packets shown in the table are used to support the primitives of the BIS. Other packets not contained in the table may be essential, but have no relation to the provision of the BIS.

2 The information in the fields shown in the table has a direct relationship to the parameters associated with the primitives of the BIS. Other fields not shown in the table (e.g. Logical Channel Identifier, Packet Type Identifier) are essential to the use of the appropriate packets.

3 All user data fields are octet aligned.

4 Facilities are optional in the BIS. See also 11.5.3 below.

| | + +### 11.5.3 Facilities of the X.25/PLP used to support the BIS + +No facility is required to support the BIS, however the following facilities have a relation to the provision of the BIS: + +- Fast Select, no restriction on response; +- Fast Select Acceptance; +- Calling/Called Address Extension. + +The usage of **Fast Select with no restriction on response** is optional. Two coding procedures for Call User Data to be transferred in call set-up packets are defined at the higher layers, dependent on whether Fast Select is used (on a per call basis) or not. The usage is a local matter. If it is not used, the Clear User Data Field is empty and the corresponding parameter(s) cannot be used for information exchange between the higher layers and the Network Layer (see Notes in 7.2.1, 7.2.2, 8.3.1 and 8.3.2). + +The **Fast Select with restriction on response** facility shall not be used. + +The use of the **Calling/Called Address Extension** facility to identify a BISAP unambiguously depends on local operation requirements and is optional. + +## 11.6 Network connection establishment phase + +NOTE – Out-Band related matters are out of the scope of this Recommendation (see 11.3.1). + +### 11.6.1 Primitive/parameter and packet/field relationships + +Table 57 shows the relationships between the primitives parameters and the packets/fields for the network connection establishment phase. + +TABLE 57/T.105 + +**BIS/X.25 mapping for the network connection establishment phase** + +| BIS | X.25/PLP | +|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| PRIMITIVES
BIS-N-CONNECT request
BIS-N-CONNECT indication
BIS-N-CONNECT response
BIS-N-CONNECT confirm | PACKETS
CALL REQUEST
INCOMING CALL
CALL ACCEPTED
CALL CONNECTED | +| PARAMETERS
Called Address

Calling Address

Responding Address

BIS-user-data | FIELDS
Called DTE Address field
Called Address Extension facility (Note 1)

Calling DTE Address field
Calling Address Extension facility (Note 1)

Called DTE Address field
Called Address Extension facility (Note 1)

Call and Called User Data field
Fast Select facility (Note 2)
Address field (Note 3) | +| NOTES
1 The use of the Calling/Called Address Extension facility is not mandatory for a given NC and depends on local operation requirements.
2 The support of the Fast Select facility or its use for a given NC is not mandatory. The selection of the use or non-use is a local matter.
3 The information which is related to the SBV protocol parameter IB_Called_Address may occur only when In-Band Addressing is not used. | | + +## **11.6.2 Procedures** + +### **11.6.2.1 General Function** + +The NC establishment service primitives can be used to establish an NC, provided the BIS users exist and are known to the BIS provider. + +Simultaneous BIS-N-CONNECT primitives at the two BISAPs are handled independently by the BIS provider. They may result in two, one or zero NCs. Part a) in Figure 15 indicates a valid sequence of BIS primitives for successful NC establishment. + +### **11.6.2.2 Primitive/packet mapping** + +When an NL entity receives a BIS-N-CONNECT request from a BIS user and is able to set up a VC, it transmits a CALL REQUEST packet across the DTE/DXE interface. Otherwise, it issues a BIS-N-DISCONNECT indication to the BIS user. + +NOTE 1 – A reason for not being able to set up a VC could be that currently no LC is available. + +When an NL entity receives a BIS-N-CONNECT response from a BIS user, it transmits a CALL ACCEPTED packet across the DTE/DXE interface. + +When an NL entity receives an INCOMING CALL packet and is able to accept the call, it signals a BIS-N-CONNECT indication to the BIS user. The NL entity may also for internal reasons reject the call by sending a CLEAR REQUEST packet across the DTE/DXE interface. In this case no service primitive is passed to the BIS user. + +NOTE 2 – A possible reason for rejecting the call could be that the NL entity chooses to consider QOS aspects and the required QOS cannot be achieved for this call. + +When an NL entity receives a CALL CONNECTED packet, it signals a BIS-N-CONNECT confirm primitive to the BIS user. + +### **11.6.2.3 Addresses** + +The contents of the address fields are determined by local operation. + +### **11.6.2.4 User data** + +The call user data field of X.25/PLP CALL REQUEST and INCOMING CALL packets is used to transfer the BIS-user-data of BIS-N-CONNECT request and indication primitives, respectively. The called user data field of X.25/PLP CALL ACCEPTED and CALL CONNECTED packets is used to transfer the BIS-user-data of BIS-N-CONNECT response and confirm primitives, respectively. + +NOTE – In CALL ACCEPTED and CALL CONNECTED packets, the Called User Data field only exists if the Fast Select facility was used in the corresponding CALL REQUEST or INCOMING CALL packet, which is an option for the BIS. + +## **11.7 Network connection release phase** + +NOTE – Out-Band related matters are out of the scope of this Recommendation (see 11.3.1). + +### **11.7.1 Primitive/parameter and packet/field relationships** + +Table 58 shows the relationships between the primitives/parameters and the packets/fields for the network connection release phase. + +TABLE 58/T.105 + +**BIS/X.25 mapping for the network connection release phase** + +| BIS | X.25/PLP | +|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| PRIMITIVES
BIS-N-DISCONNECT request
BIS-N-DISCONNECT indication | PACKETS
CLEAR REQUEST
CLEAR INDICATION
RESTART INDICATION
CLEAR REQUEST
RESTART REQUEST | +| PARAMETERS
Originator and Reason
Responding Address
BIS-user-data | FIELDS
Cause and Diagnostic Code fields
Called DTE Address field
Called Address Extension facility (Note 1)
Clear User Data field
Fast Select facility (Note 2) | +| NOTES
1 The use of the Called Address Extension facility depends on local operation requirements.
2 The use of the facility is not mandatory. The selection of the use or non-use is a local matter. However, it has an effect on the operation of the higher layers. | | + +**11.7.2 Procedures****11.7.2.1 General Function** + +The NC release service primitives are used to an NC. The NC release may be performed: + +- a) by either or both of the BIS users to release an established NC; +- b) by the BIS provider to release an established NC; all failures to maintain an NC are indicated this way; +- c) by the called BIS user to reject a BIS-N-CONNECT indication; +- d) by the BIS provider to indicate its inability to establish a requested NC. + +Valid sequences of service primitives including NC release service primitives are shown in parts b) to g) of Figure 15. + +NC release is permitted at any time regardless of the current phase of the NC. Once an NC release procedure has been invoked, the NC will be released: a request for NC release cannot be rejected. After NC release has been invoked at one NC endpoint, the BIS provider may discard any unqualified and qualified BIS user data that has not yet been delivered at the other NC endpoint and may cause any uncompleted sequence of primitives for NC establishment or reset to remain uncompleted. + +**11.7.2.2 Primitive/packet mapping** + +When an NL entity receives a BIS-N-DISCONNECT request primitive from a BIS user related to an NC established or in the process of being established (states 2 to 6), it transmits a CLEAR REQUEST packet across the DTE/DXE interface. + + + +## 11.8 Data transfer phase – (Unqualified) data transfer service + +### 11.8.1 Primitive/parameter and packet/field relationships + +Table 59 shows the relationships between the primitives parameters and the packets/fields for the (unqualified) data transfer service. + +TABLE 59/T.105 + +#### BIS/X.25 mapping for the (unqualified) data transfer service + +| BIS | X.25/PLP | +|---------------------------------------------------------------------------------------|----------------------------------------------------| +| PRIMITIVES
BIS-N-DATA request
BIS-N-DATA indication | PACKETS
DATA
DATA | +| PARAMETERS
BIS-user-data | FIELDS
User Data field
Q-bit (Note)
M-bit | +| NOTE – The value of the Q-bit is 0 in all packets of a complete data packet sequence. | | + +### 11.8.2 Procedures + +#### 11.8.2.1 Primitive/packet mapping + +When an NL entity receives a BIS-N-DATA request primitive from a BIS user, it transmits a sequence of one or more DATA packets, known as an M-bit sequence (MBS), across the DTE/DXE interface. The number of DATA packets needed in an MBS depends on the amount of BIS-user-data and on the maximum data packet size (i.e. the maximum User Data field length of DATA packets) permitted at the DTE/DXE interface. All DATA packets but the last one have their M-bit set to 1. The last data packet has the M-bit set to 0. All DATA packets shall have the Q-bit set to 0. + +When an NL entity receives an MBS with the Q-bit set to 0 in each DATA packet, it signals a BIS-N-DATA indication primitive to the BIS user. + +If the Q-bit setting is not the same in all DATA packets of an MBS, the Network Layer entity shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “Inconsistent Q-bit settings” (value = 83). Additionally the procedures for resetting an NC as defined below shall be followed. + +#### 11.8.2.2 User data + +The User Data field of X.25/PLP DATA packets (Q-bit = 0) is used to transfer (unqualified) BIS user data between users of the BIS. The number and sequence of the octets contained in the BIS-user-data parameter remains unchanged by the network. + +## 11.9 Data transfer phase – Qualified data transfer service (Q-bit = 1) + +### 11.9.1 Primitive/parameter and packet/field relationships + +Table 60 shows the relationships between the primitives parameters and the packets/fields for the qualified data transfer service. + +TABLE 60/T.105 + +**BIS/X.25 mapping for the qualified data transfer service** + +| BIS | X.25/PLP | +|---------------------------------------------------------------------------------------|----------------------------------------------------| +| PRIMITIVES
BIS-N-Q-DATA request
BIS-N-Q-DATA indication | PACKETS
DATA
DATA | +| PARAMETERS
BIS-user-data | FIELDS
User Data field
Q-bit (Note)
M-bit | +| NOTE – The value of the Q-bit is 1 in all packets of a complete data packet sequence. | | + +### 11.9.2 Procedures + +#### 11.9.2.1 Primitive/packet mapping + +When an NL entity receives a BIS-N-Q-DATA request primitive from a BIS user, it transmits a sequence of one or more DATA packets, known as an M-bit sequence (MBS), across the DTE/DXE interface. The number of DATA packets needed in an MBS depends on the amount of BIS user data and on the maximum data packet size (i.e. the maximum User Data field length of DATA packets) permitted at the DTE/DXE interface. All DATA packets but the last one have their M-bit set to 1. The last data packet has the M-bit set to 0. All DATA packets shall have the Q-bit set to 1. + +When an NL entity receives an MBS with the Q-bit set to 1 in each DATA packet, it signals a BIS-N-Q-DATA indication primitive to the BIS user. + +If the Q-bit setting is not the same in all DATA packets of an MBS, the Network Layer entity shall reset the logical channel indicating the cause “DTE originated” and the diagnostics “Inconsistent Q-bit settings” (value = 83). Additionally the procedures for resetting an NC as defined below shall be followed. + +#### 11.9.2.2 User data + +The User Data field of X.25/PLP DATA packets (Q-bit = 1) is used to transfer qualified BIS user data between users of the BIS. The number and sequence of the octets contained in the BIS-user-data parameter remains unchanged by the network. + +## 11.10 Data transfer phase – Reset service + +### 11.10.1 Primitive/parameter and packet/field relationships + +Table 61 shows the relationships between the primitives parameters and the packets/fields for the reset service. + +TABLE 61/T.105 + +**BIS/X.25 mapping for the reset service** + +| BIS | X.25/PLP | +|-----------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------| +| PRIMITIVES
BIS-N-RESET request
BIS-N-RESET indication

BIS-N-RESET response
BIS-N-RESET confirm | PACKETS
RESET REQUEST
RESET INDICATION
RESET REQUEST

none (Note)
none (Note) | +| PARAMETERS
Originator and Reason | FIELDS
Cause and Diagnostic Code fields | +| NOTE – There may be, but there need not be a relation to RESET packets. See also 11.10.2.2 below. | | + +**11.10.2 Procedures****11.10.2.1 General Function** + +The reset service may be used: + +- a) by the BIS user to resynchronize the use of the NC; or +- b) by the BIS provider to report detected loss of BIS user data unrecoverable within the BIS. All loss of user data which does not involve loss of the NC is reported this way. + +All user data within the network and not delivered to the BIS user before completion of the reset service will be discarded by the BIS provider. + +Valid sequences of primitives providing the reset service can be found in parts j) to m) of Figure 15. + +**11.10.2.2 Primitive/packet mapping** + +When an NL entity receives a BIS-N-RESET request primitive from a BIS user, it transmits a RESET REQUEST packet across the DTE/DXE interface. When the NL entity is ready to accept subsequent unqualified and qualified data from the BIS user, it signals an BIS-N-RESET confirm primitive. The issuing of this primitive may or may not be related to the completion of the X.25/PLP Reset procedure. Any unqualified data or qualified data received from the BIS user following the BIS-N-RESET confirm primitive is transmitted after completion of the X.25/PLP Reset procedure. + +If an NL entity detects an error in the operation of the X.25/PLP for which its action is to reset the virtual circuit (e.g. after a sequence error), then it transmits a RESET REQUEST packet across the DTE/DXE interface. When the NL entity is ready to accept subsequent unqualified data and qualified data from the BIS user, it signals a BIS-N-RESET indication primitive. The issuing of this primitive may or may not be related to the completion of the X.25/PLP Reset procedure. Any unqualified data or qualified data received from the BIS user following the BIS-N-RESET response primitive is transmitted after completion of the X.25/PLP Reset procedure. + +When an NL entity receives a RESET INDICATION or REQUEST packet, it signals a BIS-N-RESET indication primitive to the BIS user. + +When a BIS-N-RESET response primitive is received from the BIS user, the NL entity shall be willing to accept subsequent unqualified data or qualified data from the BIS user used for transmission upon completion of the X.25/PLP Reset procedure. + +During the Reset process, the following actions are taken by the NL entity with respect to the operation of the X.25/PLP: + +- a) For DATA or qualified DATA packets: + - those awaiting transmission may either be transmitted prior to transmitting a RESET packet or flushed from the queue of DATA packets awaiting transmission; + - those remaining in the transmit window when the Reset procedure is completed are flushed; and + - those that have been received prior to receiving a RESET packet but which do not constitute an entire MBS are flushed from the “MBS reassembly area”. +- b) The lower window edge for each direction of data transmission is set to 0 and subsequently transmitted DATA or qualified DATA packets are numbered starting from 0. +- c) Any busy condition that had existed prior to the reset is considered not to exist any longer. +- d) All timer and retransmission parameters relating to data transfer are set back to their initial value. + +No action is required with respect to the provision of the BIS by an NL entity when it receives a RESET CONFIRMATION packet, or a RESET INDICATION/REQUEST packet in response to a RESET REQUEST packet (i.e. a reset collision). However, it shall then be capable of receiving subsequent DATA packets. + +### 11.10.2.3 Originator and Reason + +The combination of Originator and Reason parameters of the BIS-N-RESET primitives is mapped to/from the combination of Resetting Cause and Diagnostic Code fields. + +In case of a BIS-N-RESET request (originator parameter absent), the NL entity inserts the value of “DTE originated” into the Resetting Cause field of the RESET REQUEST packet. + +## 11.11 Data Transfer-Phase – Interrupt transfer service + +### 11.11.1 Primitive/parameter and packet/field relationships + +Table 62 shows the relationships between the primitives parameters and the packets/fields for the interrupt transfer service. + +TABLE 62/T.105 + +**BIS/X.25 mapping for the interrupt transfer service** + +| BIS | X.25/PLP | +|---------------------------------------------------------------------|-------------------------------------| +| PRIMITIVES
BIS-N-INTERRUPT request
BIS-N-INTERRUPT indication | PACKETS
INTERRUPT
INTERRUPT | +| PARAMETERS
BIS-Interrupt-User-Data | FIELDS
Interrupt User Data field | + +### 11.11.2 Procedures + +#### 11.11.2.1 Primitive/packet mapping + +When an NL entity receives a BIS-N-INTERRUPT request primitive from a BIS user, it transmits one INTERRUPT packet across the DTE/DXE interface. + +When an NL entity receives an INTERRUPT packet, it signals a BIS-N-INTERRUPT indication primitive to the BIS user. + +### 11.11.2.2 User data + +The Interrupt User Data field of X.25/PLP INTERRUPT packets is used to transfer BIS interrupt user data between users of the BIS. The number and sequence of the octets contained in the BIS-interrupt-user-data parameter remains unchanged by the network. + +## Annex A + +### Examples of configurations + +(This annex does not form an integral part of this Recommendation) + +#### A.1 Symbols + +The following symbols in Figure A.1 are used in this annex: + +![Figure A.1/T.105: Symbols. This diagram defines three symbols used in the annex. 1. A triangle pointing right, labeled '(I)VT', representing an 'ISDN syntax-based Videotex Terminal'. 2. A triangle pointing left, labeled 'IVAP', representing an 'ISDN syntax-based Videotex Access Point'. 3. A square labeled 'VH', representing a 'Videotex Host'. Below the symbols, the reference 'T0815200-94/d07' is provided.](18dbea0ac6b7ad13e47afda3ddd53b64_img.jpg) + +ISDN syntax-based Videotex Terminal + +ISDN syntax-based Videotex Access Point + +Videotex Host + +T0815200-94/d07 + +Figure A.1/T.105: Symbols. This diagram defines three symbols used in the annex. 1. A triangle pointing right, labeled '(I)VT', representing an 'ISDN syntax-based Videotex Terminal'. 2. A triangle pointing left, labeled 'IVAP', representing an 'ISDN syntax-based Videotex Access Point'. 3. A square labeled 'VH', representing a 'Videotex Host'. Below the symbols, the reference 'T0815200-94/d07' is provided. + +FIGURE A.1/T.105 + +#### Symbols + +#### A.2 Access to PSTN/PSPDN systems using a terminal adaptor + +These configurations are intended to access Videotex Services (VS), designed for use on the PSTN, via an ISDN. The services offered to the user should be identical to the service offered via a PSTN/PSPDN. As a consequence, the protocols to be used at the terminal side are those used for the access of PSTN/PSPDN Videotex Services. + +These configurations are outside the scope of this Recommendation. + +##### A.2.1 Analogue terminal adaptors + +An ISDN may be utilized as an analogue telephone network (via the 3,1 kHz audio bearer service) using analogue terminal adaptors (TA). Both sides require modems. As shown in Figure A.2, the interworking unit between ISDN and PSTN can be used. + +![Figure A.2/T.105: Access of PSTN/PSPDN systems via analogue terminal Adaptors. This block diagram shows the connection between an ISDN network and a PSTN network. On the left, a Videotex Terminal (VT, represented by a triangle) is connected to a Modem, which is then connected to an Analogue Terminal Adaptor (TA). On the right, a Videotex Host (VH, represented by a square) is connected to a Modem, which is then connected to another Analogue Terminal Adaptor (TA). The two Analogue TAs are connected to the ISDN network (represented by an oval). The ISDN network is connected to a central 'Interworking Functions' block (represented by a rectangle with a diagonal line). This block is connected to the PSTN network (represented by an oval). The PSTN network is then connected back to the two Analogue TAs, completing the loop.](0549ab3c68ad94e7e1bb6ec6aa6b5373_img.jpg) + +Analogue TA + +ISDN + +Analogue TA + +Interworking Functions + +PSTN + +Modem + +Modem + +VT + +VH + +T0815210-94/d08 + +Figure A.2/T.105: Access of PSTN/PSPDN systems via analogue terminal Adaptors. This block diagram shows the connection between an ISDN network and a PSTN network. On the left, a Videotex Terminal (VT, represented by a triangle) is connected to a Modem, which is then connected to an Analogue Terminal Adaptor (TA). On the right, a Videotex Host (VH, represented by a square) is connected to a Modem, which is then connected to another Analogue Terminal Adaptor (TA). The two Analogue TAs are connected to the ISDN network (represented by an oval). The ISDN network is connected to a central 'Interworking Functions' block (represented by a rectangle with a diagonal line). This block is connected to the PSTN network (represented by an oval). The PSTN network is then connected back to the two Analogue TAs, completing the loop. + +FIGURE A.2/T.105 + +#### Access of PSTN/PSPDN systems via analogue terminal Adaptors + +### A.2.2 Rate adapting terminal adaptors + +Rate adapting terminal adaptors provide an end-to-end digital connection which transforms the digital 64 kbit/s link into an asynchronous V.24 link. No modems are needed, as shown in Figure A.3. + +![Diagram of Figure A.3 showing the connection between a Videotex Terminal (VT) and a Videotex Host (VH) via ISDN using Rate Adapting Terminal Adaptors (TA).](cd3e29b6d40dce0580fa43b721157489_img.jpg) + +The diagram illustrates a connection between a Videotex Terminal (VT) and a Videotex Host (VH) through an ISDN network. On the left, a triangle labeled 'VT' is connected to a box labeled 'Rate adapting TA'. This box is connected to an oval labeled 'ISDN'. The 'ISDN' oval is connected to another box labeled 'Rate adapting TA', which is then connected to a box labeled 'VH' on the right. The reference T0815220-94/d09 is located at the bottom right. + +Diagram of Figure A.3 showing the connection between a Videotex Terminal (VT) and a Videotex Host (VH) via ISDN using Rate Adapting Terminal Adaptors (TA). + +FIGURE A.3/T.105 +Access of PSTN/PSPDN systems via rate adapting terminal adaptors + +### A.3 Connection to a VS via ISDN + +The ISDN Videotex Terminal is connected directly to a Videotex Service via the ISDN. At the protocol level, one connection is established between the terminal and the Videotex Service (see Figures A.4 and A.5). + +![Diagram of Figure A.4 showing a direct connection between an ISDN Videotex Terminal (IVT) and a Videotex Service (VS) via ISDN.](efb282bed9f06eef1987a14fb27bc599_img.jpg) + +The diagram shows a direct connection between an ISDN Videotex Terminal (IVT) and a Videotex Service (VS) via ISDN. On the left, a triangle labeled 'IVT' is connected to an oval labeled 'ISDN'. The 'ISDN' oval is connected to a box labeled 'VS' on the right. The reference T0815230-94/d10 is located at the bottom right. + +Diagram of Figure A.4 showing a direct connection between an ISDN Videotex Terminal (IVT) and a Videotex Service (VS) via ISDN. + +FIGURE A.4/T.105 +Connection to a VS via ISDN + +![Diagram of Figure A.5 showing the protocol stack for IVT-VS connection.](71f0fd23b2f06b621ba89a65ee3c284c_img.jpg) + +The diagram illustrates the protocol stack for the connection between an ISDN Videotex Terminal (IVT) and a Videotex Service (VS). At the top, two boxes labeled 'Terminal Application' and 'Service Application' are connected by a horizontal line. Below each box is a vertical stack of four layers, numbered 1 to 7 from bottom to top. The layers are connected by horizontal lines between the IVT and VS stacks. The reference T0815240-94/d11 is located at the bottom right. + +Diagram of Figure A.5 showing the protocol stack for IVT-VS connection. + +FIGURE A.5/T.105 +Protocol stack for IVT-VS connection + +## A.4 Access to a VS via an ISDN/PSPDN + +A Videotex Service is made available over the ISDN, using the interworking mechanisms between the ISDN and the PSPDN as defined in CCITT Recommendation X.31 for either case A or case B. These topologies imply that the packet interworking unit [an Access Unit (AU) in case A, a Packet Handler (PH) in case B] is addressed over the ISDN and the B-channel (or optionally the D-channel for case B) is used to establish a connection with the Videotex Service (see Figures A.6 and A.7). + +![Figure A.6/T.105: Access to a VS via ISDN/PSPDN. A high-level diagram showing an IVT (triangle) connected to a combined ISDN/PSPDN oval, which is then connected to a VS (rectangle).](e93f2f4b0bf7e94139c1a2f1357962da_img.jpg) + +T0815250-94/d12 + +Figure A.6/T.105: Access to a VS via ISDN/PSPDN. A high-level diagram showing an IVT (triangle) connected to a combined ISDN/PSPDN oval, which is then connected to a VS (rectangle). + +FIGURE A.6/T.105 +Access to a VS via ISDN/PSPDN + +![Figure A.7/T.105: Protocol stack for IVT-AU/PH-VS connection. A detailed diagram showing the protocol stacks for the IVT, AU or PH, and VS. The IVT stack has layers 1, 2, 3, and 7. The AU or PH stack has layers 1, 2, and 3. The VS stack has layer 7. Arrows indicate connections between layers 1, 2, and 3 of the IVT and AU or PH, and between layer 3 of the AU or PH and layer 7 of the VS. A horizontal line connects the Terminal Application and Service Application boxes at the top.](b87818c8505328b198d035761bbc3f2d_img.jpg) + +(1) CCITT Rec. X.31 access + +T0815260-94/D13 + +Figure A.7/T.105: Protocol stack for IVT-AU/PH-VS connection. A detailed diagram showing the protocol stacks for the IVT, AU or PH, and VS. The IVT stack has layers 1, 2, 3, and 7. The AU or PH stack has layers 1, 2, and 3. The VS stack has layer 7. Arrows indicate connections between layers 1, 2, and 3 of the IVT and AU or PH, and between layer 3 of the AU or PH and layer 7 of the VS. A horizontal line connects the Terminal Application and Service Application boxes at the top. + +FIGURE A.7/T.105 +Protocol stack for IVT-AU/PH-VS connection + +## A.5 Access to a VS via an IVAP + +The terminal accesses a Videotex Service via an ISDN Videotex Access Point. The Host Access Network should be a PDN (generally a PSPDN) or an ISDN (see Figure A.8). + +The connection establishment with the host does not have any influence on the protocol stack between the terminal and the IVAP. As far as the terminal is concerned, only a connection to the IVAP exists. + +In terms of the protocol stack in the B-channel, there is an end-to-end connection on layer 3 between the two sides, with an Application Layer on top (see Figure A.9). + +![Figure A.8/T.105: Connection via an IVAP. A sequence diagram showing the connection path: IVT (triangle) -> ISDN (oval) -> IVAP (triangle) -> HAN (oval) -> VH (rectangle).](24ba47df8be44ae91945d88ce2232df5_img.jpg) + +T0815270-94/d14 + +Figure A.8/T.105: Connection via an IVAP. A sequence diagram showing the connection path: IVT (triangle) -> ISDN (oval) -> IVAP (triangle) -> HAN (oval) -> VH (rectangle). + +FIGURE A.8/T.105 +**Connection via an IVAP** + +![Figure A.9/T.105: Protocol stack for IVT-IVAP-VH connection. A diagram showing three protocol stacks for IVT, IVAP, and VH. Each stack has four layers labeled 1, 2, 3, and 7. Above each stack is a box: 'Terminal Application' for IVT, 'Access functionality' for IVAP, and 'Host Application' for VH. Lines connect the corresponding layers between adjacent stacks: 7 to 7, 3 to 3, 2 to 2, and 1 to 1.](364054adcd1b427fa259450e006c6b38_img.jpg) + +T0815280-94/d15 + +Figure A.9/T.105: Protocol stack for IVT-IVAP-VH connection. A diagram showing three protocol stacks for IVT, IVAP, and VH. Each stack has four layers labeled 1, 2, 3, and 7. Above each stack is a box: 'Terminal Application' for IVT, 'Access functionality' for IVAP, and 'Host Application' for VH. Lines connect the corresponding layers between adjacent stacks: 7 to 7, 3 to 3, 2 to 2, and 1 to 1. + +FIGURE A.9/T.105 +**Protocol stack for IVT-IVAP-VH connection** + +### A.5.1 Service selection after a dialogue with the IVAP + +The terminal is connected to an IVAP, which sets up a second connection to a server after some dialogue between the terminal and the IVAP. This is basically a refinement of the access to a VH (see Figure A.10). + +### A.5.2 Service selection using a VS identification + +A B-channel is established between the terminal and the IVAP. On this B-channel, layer 2 and layer 3 are set up. The layer 3 CALL REQUEST carries the address or the name of the requested application. This information is used by the IVAP to establish an end-to-end dialogue between the terminal and the VH (see Figure A.11). + +#### A.5.2.1 VS identified by a network address + +The application is selected by its VH-address on the Host Access Network. This address is inserted in the layer 3 CALL REQUEST and interpreted by the IVAP to establish a connection with the VH. + +**EXAMPLE:** Assume that the VH-address is “12345678”. This number is inserted in the layer 3 CALL REQUEST sent by the terminal to the IVAP. + +**NOTE –** Some user data (e.g. user-identification) may be associated with the VH-address. It is conveyed transparently from the terminal to the VH. + +![Diagram of connection establishment after dialogue between IVT, ISDN, IVAP, HAN, and VH.](0adfaa8c2562a9fe3a8a96165d7d59a3_img.jpg) + +The diagram illustrates the sequence of events for connection establishment after a dialogue. It shows a sequence of components: IVT (triangle), ISDN (oval), IVAP (triangle), HAN (oval), and VH (square). Below the sequence, horizontal lines represent the duration of various processes: + +- B-channel-establishment**: A single line spanning from the start of IVT to the end of IVAP. +- Layer 2 set-up**: A line spanning from the start of IVT to the end of HAN. +- Layer 3 set-up**: A line spanning from the start of IVT to the end of HAN. +- Dialogue set-up**: A line spanning from the start of IVT to the end of HAN. +- Dialogue**: A long line spanning from the start of IVT to the end of VH. + +T0815290-94/d16 + +Diagram of connection establishment after dialogue between IVT, ISDN, IVAP, HAN, and VH. + +FIGURE A.10/T.105 +Connection establishment after dialogue + +![Diagram of connection establishment without dialogue between IVT, ISDN, IVAP, HAN, and VH.](b1784a5cbeeb3d9fb9e60b333019c721_img.jpg) + +The diagram illustrates the sequence of events for connection establishment without a dialogue. It shows a sequence of components: IVT (triangle), ISDN (oval), IVAP (triangle), HAN (oval), and VH (square). Below the sequence, horizontal lines represent the duration of various processes: + +- B-channel-establishment**: A single line spanning from the start of IVT to the end of IVAP. +- Layer 2 set-up**: A line spanning from the start of IVT to the end of HAN. +- Layer 3 set-up**: A line spanning from the start of IVT to the end of HAN. +- Dialogue set-up**: A line spanning from the start of IVT to the end of HAN. +- Dialogue**: A long line spanning from the start of IVT to the end of VH. + +T0815300-94/d17 + +Diagram of connection establishment without dialogue between IVT, ISDN, IVAP, HAN, and VH. + +FIGURE A.11/T.105 +Connection establishment without dialogue + +#### A.5.2.2 VS identified by a name + +The requested application is identified by a Videotex Service name. This name is inserted by the terminal in the layer 3 CALL REQUEST and interpreted by the IVAP to establish the appropriate connection. + +EXAMPLE: Assume that the Videotex Service name is “ETSI”. This name is inserted in the layer 3 CALL REQUEST and translated by the IVAP into the VH-address “12345678”. + +#### A.5.3 Service selection using ISDN supplementary services + +In these configurations, ISDN supplementary services are used to convey service selection information before establishing a B-channel. This information can be used by the IVAP to select the appropriate application. + +The usage of these mechanisms is independent of selection mechanisms which use B-channel protocols. Both mechanisms may be used together. + +For more details on supplementary services, refer to Annex B (informative). + +#### A.5.4 Distributed Videotex Application + +See Figure A.12. + +![Diagram of Distributed Videotex Host configuration showing IVT, ISDN, IVAP, HAN1, HAN2, HANn, VH1, VH2, and VHn.](d510bddda14c44163bbeee33b491a105_img.jpg) + +The diagram illustrates the Distributed Videotex Host configuration. It shows a sequence of components: IVT (represented by a triangle), ISDN (represented by an oval), IVAP (represented by a triangle), and a set of Hosts (HAN1, HAN2, ..., HANn, each in an oval) connected to Video Hosts (VH1, VH2, ..., VHn, each in a rectangle). The IVT is connected to ISDN, which is connected to IVAP. IVAP is connected to HAN1, HAN2, and HANn. HAN1 is connected to VH1, HAN2 to VH2, and HANn to VHn. The reference T0815310-94/d18 is located at the bottom right. + +Diagram of Distributed Videotex Host configuration showing IVT, ISDN, IVAP, HAN1, HAN2, HANn, VH1, VH2, and VHn. + +FIGURE A.12/T.105 +Distributed Videotex Host configuration + +NOTE – If one of the hosts is accessible only directly via a PSTN or PSPDN, the resulting configuration is outside the scope of this Recommendation. + +##### A.5.4.1 Usage of a single VC between IVT and IVAP + +The terminal is connected to the IVAP or VH1 using a VC on the B-channel. When the application requires the terminal to be connected to VH2, the IVAP should establish a VC to VH2 upon the reception of a specific request from VH1 (see Figure A.13). + +![Diagram of Distributed hosts via a single VC showing IVT, ISDN, IVAP, HAN1, HAN2, VH1, and VH2, with a legend for Dialogue, Request VH2, and Connection set-up.](afd9ce64c136f2090b978ea5f3ef9d8d_img.jpg) + +The diagram illustrates the usage of a single VC between IVT and IVAP. It shows the same components as Figure A.12: IVT, ISDN, IVAP, HAN1, HAN2, VH1, and VH2. The IVT is connected to ISDN, which is connected to IVAP. IVAP is connected to HAN1 and HAN2. HAN1 is connected to VH1, and HAN2 is connected to VH2. Below the diagram, a legend defines the communication flow: 'Dialogue' is a long double-headed arrow between IVT and IVAP; 'Request VH2' is an arrow from VH1 to IVAP; 'Connection set-up' is an arrow from IVAP to VH2. The reference T0815320-94/d19 is located at the bottom right. + +Diagram of Distributed hosts via a single VC showing IVT, ISDN, IVAP, HAN1, HAN2, VH1, and VH2, with a legend for Dialogue, Request VH2, and Connection set-up. + +FIGURE A.13/T.105 +Distributed hosts via a single VC + +The terminal is linked to the IVAP via one single VC on one single B-channel, while the IVAP is connected to more than one VH. The IVAP should perform the multiplexing of informations received from VH1 and VH2 onto the one single VC to the terminal. + +From a protocol standpoint at the terminal side, this configuration is exactly identical with the one described in A.4. + +#### A.5.4.2 Establishment of the second VC by the IVT + +The terminal is connected to the IVAP or VH1 using a VC on a B-channel. After having received a specific command from the IVAP or VH1, the terminal should establish a second VC on the same B-channel to VH2 (see Figure A.14). + +The terminal should present all the informations which are received on the two different VCs. It should also be able to interpret a specific command requesting the setting up of a second VC. + +![Diagram of a video terminal configuration with two virtual channels.](18d7d8de298d79e7bc87af5217f11203_img.jpg) + +The diagram illustrates a network topology for a video terminal (IVT) connected to two video hosts (VH1 and VH2) via a video multiplexing unit (IVAP). The IVT is connected to the IVAP through a network (RNIS). The IVAP is connected to both VH1 and VH2 through two separate hosts (HAN1 and HAN2). Below the topology, three communication paths are indicated: 'Dialogue' between the IVT and VH1, 'Demande VH2' from VH1 to the IVAP, and 'Etab. de connexion' from the IVAP to VH2. The reference T0815330-94/d20 is noted in the bottom right corner of the diagram area. + +Diagram of a video terminal configuration with two virtual channels. + +FIGURE A.14/T.105 + +**Serveurs répartis via deux communications virtuelles établies par le terminal vidéotex** + +#### A.5.4.3 Establishment of the second VC by the IVAP + +The terminal is connected to the IVAP or VH1 using a VC on the B-channel. When the application requires the terminal to be connected to VH2, the IVAP establishes a second VC connection to both VH2 and the terminal on the same B-channel. If the application is run on VH1, the second VC is established after having received a specific request from VH1 (see Figure A.15). + +In this configuration, the terminal should present the informations which are received on two different VCs. It must also be able to accept a VC set-up. + +### A.6 Host to terminal call establishment + +In all configurations described above, the initiative to establish the connection may also be taken by an IVAP. Therefore, a terminal should be able to respond to incoming calls. The topology of the network behind the IVAP is irrelevant (see Figure A.16). + +After establishment of layer 3, the same procedures apply as for all above configurations, except for the connection establishment in conjunction with a direct service selection and the service selection using ISDN supplementary services. + +### A.7 Terminal to terminal communication + +If the IVAP in the above Figure A.16 is replaced by another terminal, the resulting configuration allows for a direct terminal to terminal communication, as shown in Figure A.17. + +After establishment of layer 3, none of the service selection procedures are applicable. The Application Layer protocol does not contain any special support for this configuration. + +![Diagram of distributed hosts via two VCs initiated by the IVAP. The diagram shows an IVT (Ingress Virtual Terminal) connected to an ISDN network, which is connected to an IVAP (Ingress Virtual Access Point). The IVAP is connected to two HANs (Host Access Networks), HAN1 and HAN2, which are connected to two VCs (Virtual Channels), VH1 and VH2. Below the diagram, a sequence of events is shown: 'Dialogue' (a long double-headed arrow), 'Request VH2' (an arrow from VH1 to VH2), and 'Connection set-up' (two arrows, one from IVT to VH1 and one from IVT to VH2).](5cc4a2ef554f31ea0577731931007fff_img.jpg) + +T0815340-94/d21 + +Diagram of distributed hosts via two VCs initiated by the IVAP. The diagram shows an IVT (Ingress Virtual Terminal) connected to an ISDN network, which is connected to an IVAP (Ingress Virtual Access Point). The IVAP is connected to two HANs (Host Access Networks), HAN1 and HAN2, which are connected to two VCs (Virtual Channels), VH1 and VH2. Below the diagram, a sequence of events is shown: 'Dialogue' (a long double-headed arrow), 'Request VH2' (an arrow from VH1 to VH2), and 'Connection set-up' (two arrows, one from IVT to VH1 and one from IVT to VH2). + +FIGURE A.15/T.105 +Distributed hosts via two VCs initiated by the IVAP + +![Diagram of host to terminal connection establishment. The diagram shows an IVT (Ingress Virtual Terminal) connected to an ISDN network, which is connected to an IVAP (Ingress Virtual Access Point). Below the diagram, a sequence of events is shown: 'B-channel establ.' (a long arrow from IVT to IVAP), 'Layer 2 set-up' (a long arrow from IVT to IVAP), and 'Layer 3 set-up' (a long arrow from IVT to IVAP).](2b60ebe01f77d22e53da1fbe73083b01_img.jpg) + +T0815350-94/d22 + +Diagram of host to terminal connection establishment. The diagram shows an IVT (Ingress Virtual Terminal) connected to an ISDN network, which is connected to an IVAP (Ingress Virtual Access Point). Below the diagram, a sequence of events is shown: 'B-channel establ.' (a long arrow from IVT to IVAP), 'Layer 2 set-up' (a long arrow from IVT to IVAP), and 'Layer 3 set-up' (a long arrow from IVT to IVAP). + +FIGURE A.16/T.105 +Host to terminal connection establishment + +![Diagram of terminal to terminal communication. The diagram shows two IVTs (Ingress Virtual Terminals) connected to an ISDN network. Below the diagram, a sequence of events is shown: 'B-channel establishment' (a long arrow from the left IVT to the right IVT), 'Layer 2 set-up' (a long arrow from the left IVT to the right IVT), and 'Layer 3 set-up' (a long arrow from the left IVT to the right IVT).](1c79f31a718d63814feb28ab46f64f19_img.jpg) + +T0815360-94/d23 + +Diagram of terminal to terminal communication. The diagram shows two IVTs (Ingress Virtual Terminals) connected to an ISDN network. Below the diagram, a sequence of events is shown: 'B-channel establishment' (a long arrow from the left IVT to the right IVT), 'Layer 2 set-up' (a long arrow from the left IVT to the right IVT), and 'Layer 3 set-up' (a long arrow from the left IVT to the right IVT). + +FIGURE A.17/T.105 +Terminal to terminal communication + +## **Annex B** + +### **Usage of supplementary services** + +(This annex does not form an integral part of this Recommendation) + +This annex gives an overview of the supplementary services which may be used in Syntax-based Videotex in case of an ISDN. The utilization of any supplementary service is optional. + +NOTE – The use of supplementary services applies only to communications in the circuit-switched mode using a DTE/DTE connection in the Network Layer. For all other cases, the use of supplementary services is under study. + +#### **B.1 User-to-User Signalling (UUS)** + +The UUS supplementary service allows an ISDN user to send/receive a limited amount of information to/from another ISDN user over the D-channel. This information is passed transparently through the network. The message size is restricted to 128 octets. + +The user can transfer user-to-user information (UUI) in different phases of the call depending on the service(s) to which the user subscribes. For the ISDN Syntax-based Videotex, only Service 1 shall be applicable. Service 1 provides for the transfer of UUI during the setup and clearing phases of a call with UUI embedded within call control messages. + +A calling party may be subscribed to UUS. The terminal should be able to enter a UUI in the SETUP message. The specification how to handle the UUS information is outside the scope of this Recommendation. + +#### **B.2 Supplementary services for addressing** + +##### **B.2.1 Multiple Subscriber Number (MSN)** + +MSN allows for more than one subscriber number being allocated to a single basic access interface. By inspecting the called number on the D-channel, terminals can decide whether they should accept a call. The interpretation of the number is up to the terminals. + +A calling party may be subscribed to MSN. This does not have any impact on the terminal-network interface unless the user is subscribed to CLIP. In this case, a terminal has to insert its subscriber number (one of the numbers assigned to the network interface) in the messages conveyed to the network. + +##### **B.2.2 Direct-Dialling-In (DDI)** + +DDI is intended to subaddress a specific terminal (or interface) on an integrated services private branch exchange (ISPBX), which is connected to the ISDN via a primary rate interface. + +A calling party may be subscribed to DDI. This does not have any impact on the terminal-network interface unless the user is subscribed to CLIP. In this case, a terminal has to insert its subscriber number (its local extension) in the messages conveyed to the network. + +##### **B.2.3 Subaddressing (SUB)** + +Subaddressing (SUB) is a mechanism to convey a number of digits to the called party which may use this information for terminal selection. The maximum size of the subaddress is 20 octets. However, for a certain period of time, the size of the subaddress can be limited to a maximum of 4 octets either within certain networks or between networks. + +A calling party may be subscribed to SUB. The terminal should be able to enter a subaddress in the SETUP message. + +##### **B.2.4 Call Deflection (CD)** + +A called party may be subscribed to CD. It can use the information conveyed through the UUS 1 supplementary service messages to deflect a call to another address. The specification how to handle the UUS information is outside the scope of this Recommendation. + +## **B.3 Supplementary services for identification** + +### **B.3.1 Calling Line Identification Presentation (CLIP)** + +A calling party may be subscribed to CLIP. If the calling party is subscribed to CLIP, the calling line number is sent to the called party as one component of the SETUP message. Generally, the calling line identification information should be inserted by the network. In specific cases, however, terminals can insert the calling line identification information in the SETUP message. This feature is mainly used on network interfaces subscribed to MSN or DDI. + +### **B.3.2 Calling Line Identification Restriction (CLIR)** + +A calling party may be subscribed to CLIR. In case the user is subscribed to permanent mode, no calling line identification is transmitted to the called party. If the user is subscribed to temporary mode, he can indicate to the network whether the calling line identification should be transmitted to the called party or not by inserting a presentation indicator in the SETUP message. + +## **Annex C** + +### **Terminal Function basic state** + +(This annex forms an integral part of this Recommendation) + +The initial state of a Terminal Function after the successful establishment of a network connection, prior to the exchange of any further protocol elements, is called basic state. In this basic state, parameters and switches shall have the default values as defined below. + +### **C.1 X.3 parameter default values** + +The default values for all X.3 parameters which are used by the Syntax-based Videotex are given in Table C.1. + +TABLE C.1/T.105 + +**CCITT Recommendation X.3 [3] Syntax-based videotex profile** + +| Parameter reference number | Parameter description | Default value | +|---------------------------------------------------------------------------------------------|-----------------------------------------------|---------------| +| 2 | Echo (M) | 0 | +| 3 | Selection of data forwarding character(s) (M) | 0 | +| 4 | Selection of idle timer delay (M) | 1 | +| 23 | Size of input field (O) | 0 | +| 24 | End of frame signals (O) | 32 | +| 25 | Extended data forwarding signals (O) | 0 | +| 26 | Display interrupt (O) | 0 | +| 28 | Diacritic character editing (O) | 0 | +| 29 | Extended echo mark (O) | 0 | +| M Mandatory
O Optional
NOTE – No default value for parameter reference 11 is defined. | | | + +## **C.2 SBV\_DFK default list** + +The SBV\_DFK default list shall be empty. + +## **C.3 SBV\_TPD default state** + +The SBV\_TPD regime shall not be established. + +## **C.4 SBV\_Escape default state** + +When implemented, any process related to an SBV\_Escape subservice shall be inactive or shall be in its idle state. + +# **Annex D** + +## **The SBV\_Escape service** + +(This annex does not form an integral part of this Recommendation) + +### **D.1 Service description** + +#### **D.1.1 Bulk Update** + +In the sense of CCITT Recommendation F.300 [1] “a Videotex service facility is an Application Layer implementation in a Videotex service, providing a specific, clearly defined facility to Videotex users” (see 2.2.1). + +One of the several possible service facilities is named “Videotex transaction (...) which allows users to create and/or modify information stored in a data base” (see 2.2.6). Another facility is named “Videotex data processing (...) which allows the user to employ processing and storage capacity at the host computer” (see 2.2.6). + +The information elements to be handled by these service facilities may be a Videotex frame (see 2.4.13) for the first case or a Videotex System field (see 2.4.16) for the latter case. + +The SBV\_Escape subservices Bulk Update as defined in this clause provide for protocol elements to use these service facilities/applications for both ISDN and PSTN access in a given Videotex Service. + +The Bulk Update subservices are based on a master/slave handshake procedure defined for a PSTN access which allows for the transmission of 8-bit coded data blocks under the control of the Videotex Application. As a consequence, this subservice has to follow some rules which are not conclusive for a sole ISDN access. + +### **D.2 Procedures** + +#### **D.2.1 Bulk Update** + +Both Terminal Function and Access Function may use the Bulk Update subservices according to the following rules. + +NOTE – Additional rules concerning possible sequences of Bulk Update protocol elements are under the responsibility of the service facility provider (see CCITT Recommendation F.300 [1], 2.1.3). + +A data block can be transmitted in portions using the BULK\_DATA subservice. The portion size depends on the Videotex Service facility attached. + +The last data portion is conveyed using either one of the subservices BULK\_LAST or BULK\_EOT. This data portion may be the only one or it may even be empty. + +BULK\_LAST indicates the last portion of the data block to be transmitted. + +BULK\_EOT indicates in addition that no further data blocks will follow. + +BULK\_CAN may be used to abort the transaction at any given time. + +### D.3 Coding + +The SBV\_Escape subservices are identified by values of the Service-ID parameter as defined in Table D.1. + +TABLE D.1/T.105 + +**Values for the Service-ID parameter** + +| SBV_Escape Subservice | Service-ID | +|--------------------------------------------------------------------------------------------------------------------------------------------|------------| +| BULK_DATA | 8/0 | +| BULK_LAST | 8/1 | +| BULK_EOT | 8/2 | +| BULK_CAN | 8/3 | +| NOTE – Telecommunication Standardization Sector Study Group 8 should be in charge of allocating code values of the SBV_Escape subservices. | | + +## Annex E + +### Extended data forwarding signals + +(This annex does not form an integral part of this Recommendation) + +The CCITT Recommendation X.3 [3] extended parameter reference 25, which is introduced in this Recommendation, defines a number of additional forwarding conditions. + +These extended data forwarding signals are not based upon a Recommendation, but originate from national and de facto standards. The following overview gives some background to the introduction of these conditions. + +NOTE – Information providers should only use forwarding conditions which are related to the system/profile being used. + +#### Sequence of two characters starting with character 1/3 + +MINITEL terminals used in the TELETEL and other profile 2 compatible networks issue these sequences when function keys are pressed. + +#### Character 1/10 + +This character (Data Collection Terminator, DCT) is used in several profile 1 orientated services to indicate to the access function, that the filling of the current form is terminated. + +#### Character 1/12 + +This character (Terminator, TER) is used in several profile 1 orientated services to indicate to the access function, that the filling of the current field is terminated. + +#### Character 2/3 + +This character (“#”) is used in several PRESTEL (profile 3) orientated services to indicate to the access function, that the filling of the current field is terminated. + +## Character 5/15 + +This character (“\_”, but on various PRESTEL terminals displayed as “#”) is used in several PRESTEL (profile 3) orientated services to indicate to the access function, that the filling of the current field is terminated. + +## Sequence of the two characters ESC “J” (1/11 4/10) + +This sequence (the END BOX sequence in a 7-bit coding structure) is used in several PRESTEL (profile 3) orientated services to indicate to the access function, that the filling of the current form is terminated. + +## Sequence of three characters starting with the two-character sequence 2/10 3/0 + +These sequences are used in several PRESTEL (profile 3) orientated services to invoke special service functions (redisplay a frame, retrieve updated information, advice of charge). They do not have a specific termination character, but a fixed command length. + +# Annex F + +## BIS constraints on ISO 8208 PICS + +(This annex forms an integral part of this Recommendation) + +### F.1 Introduction + +This annex contains a list of constraints on the status information of the ISO/IEC 8208:1990/Am.3 [16] PICS proforma, posed by the requirements of the Bearer Independent Service as defined in clause 11. The proforma is intended to be a supplement to the ISO/IEC 8208:1990/Am.3 [16] PICS proforma and all the general information (e.g. fill-in information for the client and phrasing of conditions) is valid for the constraints Tables as well. + +### F.2 Tables structure + +Each of the following Tables F.1 to F.5 contains the following columns: + +- 1) “Item” +Used to identify the conformance statement. Only those items from the ISO/IEC 8208:1990/Am.3 [16] PICS appear, for which a status change is required. +- 2) “Feature” +Used to give a short description of the item. +- 3) “8208 status” +Original status of the item. +- 4) “8208 Reference” +Related subclause(s) of ISO/IEC 8208 [15]. +- 5) “BIS Status” +Used to indicate the new status of the statement. The status values are phrased in the same way as in the original PICS. +- 6) “Support +(Yes/No)” +The client should fill in the proforma in this column, using a Yes or No for each item. + +### F.3 Constraints Tables + +#### F.3.1 Virtual circuit types + +See Table F.1. + +TABLE F.1/T.105 + +| Item | Feature | 8208 Status | 8208 Reference | References | BIS Status | Support Yes/No | +|------|---------|-------------|----------------|------------|------------|----------------| +| Vp | PVC | O.1 | | 11.2 | X | | +| Vs | VC | O.1 | 5 | 11.2 | M | | + +### F.3.2 Call setup + +See Table F.2. + +TABLE F.2/T.105 + +| Item | Feature | 8208 Status | 8208 Reference | References | BIS Status | Support Yes/No | +|------|-------------------------------|-------------|----------------|------------|------------|----------------| +| S1 | Are outgoing VCs supported? | | 5.2.1
5.2.5 | | | | +| S1a | – Fast Select, no restriction | O | 5.2.4 | 11.4.3 | O.1 | | +| S1b | – Fast Select, restriction | O | 13.16 | 11.4.3 | X | | +| S1c | – no Fast Select | O | 5.2.4 | 11.4.3 | O.1 | | + +### F.3.3 Call clearing + +See Table F.3. + +TABLE F.3/T.105 + +| Item | Feature | 8208 Status | 8208 Reference | References | BIS Status | Support Yes/No | +|------|------------------------------------------------------------------------|-------------|----------------|------------|------------|----------------| +| C1 | Is call clearing supported as:
– response to indication of clearing | O | 5.5.4
5.5.2 | 11.7 | M | | +| C2a | – aborting an outgoing VC attempt | O | 5.4 | 11.7 | M | | +| C2c | – originating clearing of an established VC | O | 5.5.1 | 11.7 | M | | + +### F.3.4 Resetting of logical channels + +See Table F.4. + +TABLE F.4/T.105 + +| Item | Feature | 8208
Status | 8208
Reference | References | BIS
Status | Support
Yes/No | +|------|-------------------------|----------------|-------------------|------------|---------------|-------------------| +| | Is resetting supported: | | 8 | | | | +| RSi | – as initiator | O | 8.1 | 11.10 | M | | +| RSr | – as responder | O | 8.2 | 11.10 | M | | + +### F.3.5 Normal data transfer and flow control + +See Table F.5. + +TABLE F.5/T.105 + +| Item | Feature | 8208
Status | 8208
Reference | References | BIS
Status | Support
Yes/No | +|------|-----------------------------------|----------------|-------------------|------------|---------------|-------------------| +| | Are the following supported: | | | | | | +| DS1 | – Sending DATA packets | O | 6.6 | 11.8; 11.9 | M | | +| DS5a | – Sending Q = 0 in DATA packets | O.10 | 6.6 | 11.8 | M | | +| DS5b | – Sending Q = 1 in DATA packets | O.10 | 6.6 | 11.9 | M | | +| DR1 | – Receiving DATA packets | O | 6.4; 6.5 | 11.8; 11.9 | M | | +| DR4b | – Receiving M = 1 in DATA packets | O | 6.4 | 11.8; 11.9 | M | | +| DR5a | – Receiving Q = 0 in DATA packets | O.11 | 6.6 | 11.8 | M | | +| DR5b | – Receiving Q = 1 in DATA packets | O.11 | 6.6 | 11.9 | M | | \ No newline at end of file diff --git a/marked/T/T-REC-T.106-199303-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg b/marked/T/T-REC-T.106-199303-I_PDF-E/2dfa6ac3edfe874f68aa0cbccaa42322_img.jpg new file mode 100644 index 0000000000000000000000000000000000000000..1a0e21b8683d770641945f27aea1bc0b4f5c29b4 --- /dev/null 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FOREWORD + +The ITU-T (Telecommunication Standardization Sector) is a permanent organ of the International Telecommunication Union (ITU). The ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. + +The World Telecommunication Standardization Conference (WTSC), which meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. + +The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1 (Helsinki, March 1-12, 1993). + +ITU-T Recommendation T.107 was prepared by ITU-T Study Group 8 (1993-1996) and was approved under the WTSC Resolution No. 1 procedure on the 11th of August 1995. + +# --- NOTE + +In this Recommendation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. + +© ITU 1996 + +All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITU. + +# CONTENTS + +| | Page | +|--------------------------------------------------------------------------------|-------------| +| 1 Scope..... | 1 | +| 2 References..... | 1 | +| 3 Definitions and abbreviations..... | 2 | +| 3.1 Definitions ..... | 2 | +| 3.2 Abbreviations..... | 3 | +| 4 General model ..... | 4 | +| 4.1 Introduction ..... | 4 | +| 4.2 Definition of the VEMMI elements..... | 4 | +| 4.2.1 VEMMI object definition and identification..... | 5 | +| 4.2.2 VEMMI component definition..... | 5 | +| 4.2.3 VEMMI component item definition..... | 6 | +| 4.2.4 Resource definition ..... | 6 | +| 4.2.5 Transfer of VEMMI objects..... | 6 | +| 4.2.6 Resource transfer ..... | 6 | +| 4.3 VEMMI plane structure model..... | 7 | +| 4.3.1 The standard plane for videotex data ..... | 7 | +| 4.3.2 The VEMMI objects plane..... | 7 | +| 4.4 Operation modes for VEMMI terminals..... | 7 | +| 4.4.1 The standard mode ..... | 7 | +| 4.4.2 The VEMMI mode..... | 7 | +| 4.4.3 Switching between standard mode and VEMMI mode ..... | 9 | +| 4.5 VEMMI elements data content ..... | 9 | +| 4.5.1 Text data definition ..... | 9 | +| 4.5.2 Bitmaps ..... | 10 | +| 4.5.3 Colour ..... | 11 | +| 4.5.4 Videotex data ..... | 11 | +| 4.5.5 Sound ..... | 11 | +| 4.5.6 Graphical data ..... | 11 | +| 4.5.7 Video data ..... | 11 | +| 4.6 VEMMI objects positioning and dimensioning ..... | 11 | +| 4.6.1 Positioning ..... | 11 | +| 4.6.2 Dimensioning..... | 12 | +| 4.7 VEMMI elements states and state parameters ..... | 13 | +| 4.7.1 Object..... | 13 | +| 4.7.2 Component..... | 16 | +| 4.8 Local action management ..... | 17 | +| 4.9 Memory considerations..... | 18 | +| 4.10 Common rules for object handling ..... | 18 | +| 4.10.1 Active state and focus management..... | 18 | +| 4.10.2 Behaviour of the modal mode..... | 19 | +| 4.10.3 Size considerations and clipping..... | 19 | +| 4.11 Local object storage..... | 19 | +| 4.12 Symbolic directory names..... | 20 | +| 4.13 Specific rules for dedicated terminals..... | 20 | +| 5 Service description ..... | 21 | +| 5.1 Service elements initiated by the VEMMI application and the terminal ..... | 23 | +| 5.2 Service elements initiated by the VEMMI application ..... | 23 | +| 5.2.1 VEMMI_Open ..... | 23 | +| 5.2.2 VEMMI_Close..... | 24 | +| 5.2.3 VEMMI_Resume..... | 24 | + +| | Page | +|--------|--------------------------------------------------------------------| +| 5.2.4 | VEMMI_Suspend ..... 24 | +| 5.2.5 | VEMMI_Identify_Term_Cap ..... 25 | +| 5.2.6 | VEMMI_Set_Options ..... 25 | +| 5.2.7 | VEMMI_Create_Object ..... 26 | +| 5.2.8 | VEMMI_Open_Object ..... 26 | +| 5.2.9 | VEMMI_Open_Blocking_Object ..... 26 | +| 5.2.10 | VEMMI_Close_Object ..... 27 | +| 5.2.11 | VEMMI_Close_All ..... 27 | +| 5.2.12 | VEMMI_Destroy_Object ..... 27 | +| 5.2.13 | VEMMI_Obj_Access_Disable ..... 27 | +| 5.2.14 | VEMMI_Obj_Access_Enable ..... 28 | +| 5.2.15 | VEMMI_Modify_Component ..... 28 | +| 5.2.16 | VEMMI_Obj_Location_Change ..... 29 | +| 5.2.17 | VEMMI_Load_Col_Table ..... 29 | +| 5.2.18 | VEMMI_Reset_Col_Table ..... 30 | +| 5.2.19 | VEMMI_Open_Application ..... 31 | +| 5.2.20 | VEMMI_Delete_Outdated_Objects ..... 31 | +| 5.2.21 | VEMMI_Store_Objects ..... 32 | +| 5.2.22 | VEMMI_Erase_Objects ..... 32 | +| 5.2.23 | VEMMI_User_Lock ..... 32 | +| 5.2.24 | VEMMI_User_Unlock ..... 32 | +| 5.2.25 | VEMMI_Resource_Transfer ..... 33 | +| 5.3 | Service elements initiated by the terminal ..... 34 | +| 5.3.1 | VEMMI_Identify_Term_Cap_Resp ..... 34 | +| 5.3.2 | VEMMI_Object_Retransmission ..... 34 | +| 5.3.3 | VEMMI_User_Data ..... 35 | +| 5.3.4 | VEMMI_Open_Application_Resp ..... 36 | +| 5.3.5 | VEMMI_Store_Objects_Resp ..... 36 | +| 5.3.6 | VEMMI_Error ..... 36 | +| 5.3.7 | VEMMI_Resource_Transfer_Abort ..... 37 | +| 6 | VEMMI objects introduction ..... 37 | +| 6.1 | The application bar ..... 38 | +| 6.1.1 | Composition ..... 38 | +| 6.2 | The button bar ..... 38 | +| 6.2.1 | Composition ..... 38 | +| 6.3 | The pop-up menu ..... 38 | +| 6.3.1 | Composition ..... 38 | +| 6.4 | The dialogue box ..... 39 | +| 6.4.1 | Composition ..... 39 | +| 6.5 | Operative object ..... 40 | +| 6.6 | Bitmap resource object ..... 41 | +| 6.7 | Videotex resource object ..... 41 | +| 6.8 | Text resource object ..... 41 | +| 6.9 | Font resource object ..... 41 | +| 6.10 | Metacode object ..... 41 | +| 6.11 | The message box ..... 41 | +| 7 | Functional description ..... 41 | +| 7.1 | General rules for the behaviour of elements ..... 41 | +| 7.1.1 | User interaction ..... 41 | +| 7.1.2 | Local actions and reports ..... 41 | +| 7.1.3 | Relationship between objects and components ..... 42 | +| 7.1.4 | Open/close of audio, video, resource and metacode objects ..... 43 | +| 7.1.5 | Maximize operation ..... 43 | +| 7.1.6 | Notational Conventions ..... 44 | +| 7.1.7 | Mnemonic ..... 44 | + +| | Page | +|---------------------------------------------|-----------------------------------------------------------------------------------| +| 7.2 | Text formats..... 44 | +| 7.2.1 | VEMMI high quality text..... 44 | +| 7.2.2 | Text labels and titles ..... 45 | +| 7.3 | The Application Bar ..... 46 | +| 7.3.1 | Composition..... 48 | +| 7.4 | The Button Bar ..... 53 | +| 7.4.1 | Composition..... 54 | +| 7.5 | The Pop-Up Menu ..... 55 | +| 7.5.1 | Composition..... 57 | +| 7.6 | The Dialogue Box..... 58 | +| 7.6.1 | Composition..... 61 | +| 7.7 | The Message Box ..... 83 | +| 7.8 | Operative object..... 85 | +| 7.9 | Bitmap resource object ..... 87 | +| 7.10 | Videotex resource object ..... 88 | +| 7.11 | Text resource object..... 88 | +| 7.12 | Font resource object..... 89 | +| 7.13 | Metacode object..... 89 | +| 7.14 | VEMMI bitmap data type definition..... 89 | +| 7.15 | The VEMMI content encoding identification catalogue..... 89 | +| 8 | Complete coded representation of the VEMMI ..... 91 | +| 8.1 | Introduction ..... 91 | +| 8.2 | Notation used..... 91 | +| 8.3 | Overall switching of coding environment ..... 91 | +| 8.3.1 | Switching into the VEMMI mode..... 91 | +| 8.3.2 | ISO/IEC 9281 [14] syntax structure..... 93 | +| 8.4 | VEMMI Command Syntax..... 95 | +| 8.5 | Objects, components..... 98 | +| 8.6 | Local actions..... 102 | +| 9 | Encoding ..... 103 | +| 9.1 | Command structure..... 103 | +| 9.2 | Object, component and attribute structure ..... 103 | +| 9.3 | Terminal symbols encoding..... 104 | +| 9.3.1 | Opcodes ..... 104 | +| 9.3.2 | Integers ..... 104 | +| 9.3.3 | Enumerated ..... 105 | +| 9.3.4 | Strings ..... 105 | +| 9.3.5 | NDC ..... 106 | +| 9.4 | Attributes and lower level symbols..... 107 | +| 9.5 | Opcodes ..... 108 | +| 9.6 | Syntax of the VEMMI_Modify_Component..... 111 | +| 9.7 | Defaults..... 113 | +| 10 | Introduction of the VEMMI service into existing Videotex Recommendations..... 116 | +| 10.1 | Introduction of the VEMMI to T.101 [4] ..... 116 | +| 10.2 | Introduction of the VEMMI to T.105 [6] ..... 116 | +| Annex A – T.51String | ..... 116 | +| A.1 | Scope ..... 116 | +| A.2 | Graphic character sets..... 116 | +| A.3 | Code extension technique ..... 119 | +| A.4 | Repertoire of the Latin based character set..... 119 | +| A.5 | Control functions ..... 119 | +| Annex B – Mandatory subset of ISO 8859 [13] | ..... 120 | +| Annex C – Minimum datatype kernel | ..... 121 | + +# SUMMARY + +This Recommendation specifies the syntax to be used by videotex or other retrieval services for implementation of an enhanced man machine interface (VEMMI). + +The VEMMI is a means to improve the ergonomics and interactivity of retrieval systems using graphical dialogue elements such as application bar, button bar, pop-up menus, dialogue box. + +The standard plane continues to receive the standard data of the underlying platform. Standard Videotex Applications can therefore run also on a VEMMI terminal. The VEMMI objects plane receives VEMMI objects. An automatic switching mechanism between standard mode and VEMMI mode is provided. + +This Recommendation defines datatypes (VEMMI-high quality text, VEMMI bitmaps) and allows the integration of other widely used datatypes (e.g. JPEG, BMP, WAVE, MIDI, Videotex) in the VEMMI dialogue. Also operative objects are defined to extent the capabilities of a VEMMI application during runtime. + +VEMMI objects can be distributed between a host and a VEMMI terminal to improve the performance of interactive applications. The VEMMI application can control (save, load, update) VEMMI objects on the terminal. + +This Recommendation contains the service description, the service elements and their coding. + +# **ENHANCED MAN MACHINE INTERFACE FOR VIDEOTEX AND OTHER RETRIEVAL SERVICES (VEMMI)** + +*(Geneva, 1995)* + +# **1 Scope** + +This Recommendation specifies the data syntax to be used by Videotex and Multimedia/Hypermedia Information retrieval services for implementation of the Videotex Enhanced Man Machine Interface (VEMMI). + +In the Videotex case, this Recommendation is applicable to both the Videotex service and the attached Videotex terminals. Those terminals may be connected to the Videotex service via the Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN) or Packet Switched Public Data Network (PSPDN). Typically, the terminals should support ISDN Syntax-Based Videotex (SBV). + +This Recommendation can also be used for any kind of retrieval service (not related to Videotex) by using the relevant underlying platform and content data types. + +# **2 References** + +The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. + +- [1] CCITT Recommendation T.50 (1992), *International Reference Alphabet (IRA) (Formerly International Alphabet No. 5 or IA5) – Information technology – 7-bit coded character set for information interchange.* +- [2] CCITT Recommendation T.51 (1992), *Latin based coded character sets for telematic services.* +- [3] ITU-T Recommendation T.52 (1993), *Non-Latin coded character sets for telematic services.* +- [4] ITU-T Recommendation T.101 (1994), *International interworking for videotex services.* +- [5] ITU-T Recommendation T.102 (1993), *Syntax-based videotex end-to-end protocols for circuit mode ISDN.* +- [6] ITU-T Recommendation T.105 (1994), *Syntax-based videotex application layer protocol.* +- [7] ITU-T Recommendation H.261 (1993), *Video codec for audiovisual services at $p \times 64$ kbit/s.* +- [8] ITU-T Recommendation H.320 (1993), *Narrow-band visual telephone systems and terminal equipment.* +- [9] ITU-T Recommendation F.300 (1993), *Videotex service.* +- [10] ISO 2022:1986, *Information Processing – ISO 7-bit and 8-bit coded character sets – Code extension techniques.* +- [11] ISO 2375:1985, *Data processing – Procedure for registration of escape sequences.* +- [12] ISO 8632:1992, *Information technology – Computer graphics – Metafile for storage and transfer of picture description information.* +- [13] ISO 8859:1987, *Information Processing - 8-bit single-byte coded graphic character sets.* +- [14] ISO 9281:1990, *Information technology – Picture coding methods.* +- [15] ISO 10646-1:1993, *Information technology – Universal Multiple-Octet Coded Character Set (UCS) – Part 1: Architecture and basic multilingual plane.* + +- [16] ISO-IS 10918-1:1994, *Digital compression and coding of continuous-tone still images. Part 1: Requirements and guidelines.* +- [17] ISO 11172-1:1993, *Information technology – Coding of moving pictures and associated audio for digital storage media up to about 1.5 Mbit/s - Part 1: Systems.* +- [18] ISO 11172-2:1993, *Information technology – Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s – Part 2. Video.* + +# 3 Definitions and abbreviations + +## 3.1 Definitions + +For the purposes of this Recommendation, the following definitions apply: + +- 3.1.1 controls:** Visual user-interface elements that allow a user to interact with data. +- 3.1.2 Defined Display Area (DDA):** See Recommendation F.300 [9]. +- 3.1.3 emphasis:** Highlighting, colour change or other visible indication of the condition of an element or choice and the effect of that condition on a user's ability to interact with that element. Emphasis can also give additional information about the state of an object. The method used to emphasize an element is terminal dependent. +- 3.1.4 label:** Text data associated with a VEMMI component to inform the user of the purpose of a particular component or item. +- 3.1.5 local manager:** See VEMMI local manager. +- 3.1.6 mnemonic:** A single, easy-to-remember alphanumeric character that activates a VEMMI Menu Choice component and validates it. A Mnemonic character can also be used to validate an active Push Button. +- 3.1.7 modal mode:** When a VEMMI object is "modal" it is not possible for the user to leave this VEMMI object to the benefit of another VEMMI object of the same application with the different possible access tools. Each attempt to access another object by the user is refused and possibly indicated by a sound signal. +- 3.1.8 resource transfer:** Mechanism to transfer files referenced by VEMMI resource objects from a VEMMI application to a VEMMI terminal. +- 3.1.9 stretched presentation:** Shrinked or enlarged display of a bitmap in order to meet given space requirements. +- 3.1.10 tiled presentation:** Repeated display of a given bitmap in horizontal and/or vertical direction in order to meet given space requirements. +- 3.1.11 videotex application:** Videotex application using encoded data, protocols and profiles, as defined in the Videotex Recommendations referred to in clause 2. A Videotex application does not use a VEMMI service, data and protocols (see Recommendation F.300 [9]). +- 3.1.12 videotex data:** Data interchanged between a Videotex application and a Videotex terminal. +- 3.1.13 validation:** User activation action followed by a confirmation of the choice with a keyboard or with a pointing device. +- 3.1.14 VEMMI application:** Application offering an enhanced man machine interface as described in this Recommendation. +- 3.1.15 VEMMI data:** VEMMI objects description and contents and VEMMI commands exchanged between the VEMMI application and the VEMMI terminal. +- 3.1.16 VEMMI local manager:** Software running in the VEMMI terminal to handle and to present the VEMMI objects that are sent to the user by the VEMMI application. +- 3.1.17 VEMMI terminal:** Terminal which is able to run a VEMMI local manager. +- 3.1.18 videotex host computer:** See Recommendation F.300 [9]. +- 3.1.19 videotex terminal:** See Recommendation F.300 [9]. + +## 3.2 Abbreviations + +For the purposes of this Recommendation, the following abbreviations apply: + +| | | +|--------|---------------------------------------------------------------------------| +| BIN | Bitmap Identification Number | +| BMP | Microsoft Windows Device-Independent Bitmap | +| CCITT | The International Telegraph and Telephone Consultative Committee | +| CD-ROM | Compact Disk-Read Only Memory | +| CGM | Computer Graphics Metafile | +| CIN | Component Identification Number | +| CMI | Coding Method Identifier | +| CR | Carriage Return | +| DDA | Defined Display Area | +| DIB | Device-Independent Bitmap | +| DRCS | Dynamically Redefinable Character Set | +| DS I | Data Syntax according to Annex B/T.101 [4] | +| DS II | Data Syntax according to Annex C/T.101 [4] | +| DS III | Data Syntax according to Annex D/T.101 [4] | +| ESC | Escape | +| ETS | European Telecommunication Standard | +| ETSI | European Telecommunications Standards Institute | +| FIN | Font Identification Number | +| G0 | Primary character set of Recommendation T.51 [2] | +| G2 | Supplementary character set of Recommendation T.51 [2] | +| GIF | Graphics Interchange Format | +| GMT | Greenwich Mean Time | +| GUI | Graphical User Interface | +| IEC | International Electrotechnical Commission | +| IRV | International Reference Version | +| IS | International Standard | +| ISDN | Integrated Services Digital Network | +| ISO | International Organization For Standardization | +| ITU-T | International Telecommunication Union – Telecommunication Standardization | +| JIS | Japanese Institute for Standardization | +| JPEG | Joint Photographic Experts Groups | +| LF | Line Feed | +| LI | Length Indicator | +| MDI | More Data Indicator | +| MIDI | Musical Instrument Digital Interface | +| MPEG | Moving Picture Experts Group | +| NDC | Normalized Device Coordinate | + +| | | +|-------|-----------------------------------------| +| OIN | Object Identification Number | +| PCD | Picture Code Delimiter | +| PCE | Picture Control Entity | +| PDE | Picture Data Entity | +| PE | Picture Element | +| PI | Picture Identifier | +| PM | Picture Mode | +| PSPDN | Packet Switched Public Data Network | +| PSTN | Packet Switched Telephone Network | +| RGB | Red Green Blue | +| SBV | Syntax-Based Videotex | +| TE | Terminal Equipment | +| TFI | Terminal Facility Identifier | +| TIN | Text Identification Number | +| TLV | Type Length Value | +| TV | Television | +| UI | User Interface | +| VEMMI | Videotex Enhanced Man Machine Interface | +| VIN | Videotex Identification Number | +| VPDE | Videotex Presentation Data Element | +| VTX | Videotex | + +# 4 General model + +## 4.1 Introduction + +Between a host and a VEMMI terminal, a VEMMI service handles: + +- general VEMMI objects as described in this Recommendation; +- data contents as defined in this Recommendation; +- data contents as referred to in this Recommendation. + +A VEMMI terminal may also handle a Videotex application using encoded data and protocols as described in the Videotex Recommendations referred to in clause 2. + +## 4.2 Definition of the VEMMI elements + +The logical units which form the structure of the VEMMI shall be named and defined as follows: + +- VEMMI objects or objects; +- VEMMI components or components; +- VEMMI component item or items. + +VEMMI element is a generic name used in this Recommendation to designate an object, a component or an item. + +An example is given Figure 1. + +![Diagram illustrating the hierarchy of VEMMI objects, components, and items.](5b4e774d63e0e0ed73801a9247755e5f_img.jpg) + +The diagram shows a large rectangle representing a VEMMI object. Inside this rectangle, there is a dashed-line rectangle representing a VEMMI component. Within the VEMMI component, there are two smaller rectangles: one labeled 'Text label:' and another labeled 'Text input :'. The 'Text input :' rectangle is connected to the 'Text label:' rectangle by a line. Below the main rectangle, a vertical line points to the label 'VEMMI object'. From the bottom of the dashed-line rectangle, a vertical line points to the label 'VEMMI component'. From the bottom of the 'Text input :' rectangle, a vertical line points to the label 'VEMMI component item'. In the bottom right corner of the main rectangle, the text 'T0815370-94/d01' is displayed. + +Diagram illustrating the hierarchy of VEMMI objects, components, and items. + +FIGURE 1/T.107 +Example showing objects/components/items + +### 4.2.1 VEMMI object definition and identification + +The following four different types of VEMMI objects are defined in this Recommendation: + +- display objects; +- operative objects; +- resource objects; +- metacode objects. + +If not stated otherwise, the term object used alone always refers to a display object. + +VEMMI objects are the logical units which are used by a VEMMI application to interact with the user. + +VEMMI objects are composed of different components. + +The objects are only defined regarding their functionality, their size and position relative to the Defined Display Area (DDA). The representation of the objects is terminal dependent. + +Every object shall be identified by an Object Identification Number (OIN) which shall be unique within a VEMMI application at any one time. + +### 4.2.2 VEMMI component definition + +VEMMI components always belong to a VEMMI object and are only valid within this object. The object, to which a component belongs, is named parent object. + +In order to transport information, components may carry a data content (see 4.5). + +The components are only defined regarding their functionality, their type of content and their size and position relative to the object. The representation of the components is terminal dependent. The representation of data content is specified either by this Recommendation (for the datatypes that are defined within this Recommendation) or by the corresponding presentation standard (for datatypes that are defined outside this Recommendation). + +Every component shall be identified by a Component Identification Number (CIN) which shall be unique within an object. + +### 4.2.3 VEMMI component item definition + +The subunit of a VEMMI component is a component item. Every item is an integral part of a component. The definition of a component item is only valid within this component. + +### 4.2.4 Resource definition + +Resources are elements which can be referenced by components or objects. One resource can be referenced by more than one element. The following resources are defined: + +- the colour table which is unique in one application; +- files stored in the terminal (identified by filenames) can contain sound data, operative objects etc.; +- a combination of a font and a set of attributes is a resource object. It is identified via a Font Identification Number (FIN); +- a bitmap is a resource object. It is identified via a Bitmap Identification Number (BIN); +- text can be a resource object. It is identified via a Text Identification Number (TIN); +- Videotex can be a resource object. It is identified via a Videotex Identification Number (VIN); +- objects sets stored in the terminal between two sessions (they are identified via attributes). + +NOTE – FIN, BIN, VIN are Object Identification Numbers (OINs). The terms FIN, BIN and VIN are only used to clearly indicate that the corresponding object is a resource object. + +### 4.2.5 Transfer of VEMMI objects + +VEMMI objects can be transmitted to the VEMMI terminal using a telecommunication network. If they are stored then in the terminal, they become local objects. VEMMI objects can also be downloaded using any filetransfer. They become local objects as well and are treated in the same way as objects transferred within the VEMMI dialogue and stored by the corresponding service primitive. VEMMI objects may also be transferred to the VEMMI terminal by postal mail (CD-ROM, diskettes, etc.). + +### 4.2.6 Resource transfer + +VEMMI resource objects can reference files that contain the resource display data. These files are called resource data files. + +VEMMI specifies the way the resource data files are transmitted to the terminal (VEMMI resource transfer). VEMMI resources data files may also be transferred to the VEMMI terminal using the file transfer used in the standard service in which the terminal operates or by postal mail (CD-ROM, diskettes, etc.). + +In order to provide a satisfactory level of quality and features matching the VEMMI functionality, the resource transfer mechanism offers the following facilities: + +- the resource transfer can be performed without the user being aware of it; +- the resource transfer can be performed as a parallel task. During the resource transfer, the user may continue to interact with the VEMMI application (although if the network speed is not sufficient, the server response time may be adversely affected by the resource transfer operation); +- the application may open a VEMMI object (window) displaying the actual status of the transfer (e.g. a graphics representing the percentage of the resource copied), and optionally offer a method to cancel, hold and resume the transfer (e.g. using buttons); +- several resource transfers can be performed independently; +- possible user interaction on the resource transfer operation (abort). + +The support of resources is optional for a VEMMI terminal. If the terminal supports the local storage facility, it shall support the VEMMI resource transfer as well. + +## 4.3 VEMMI plane structure model + +The VEMMI display model consists of two independent planes: + +- the standard data memory and standard data window; +- the VEMMI data memory and VEMMI data window. + +This model and a possible terminal structure is presented in Figure 2. + +A VEMMI terminal shall implement the behaviour of this display model. However, no assumption is made on the real physical plane structure of the terminal and how the terminal implements that plane structure model. + +The standard plane is the output area where the retrieval service used as a platform for the VEMMI service displays its data. If a Videotex service is used as a platform, the standard plane is the DDA that is used by a regular Videotex application. In the following subclauses, it is assumed that Videotex is used as a platform. However, all the rules apply as well if the underlying platform is different from Videotex (e.g. VT100, TV-Channel). + +The two output planes are independent with respect to their positions and dimensions on the terminal screen. + +### 4.3.1 The standard plane for videotex data + +The standard plane receives standard Videotex data. It shall continue to support the Videotex data rules and priorities defined in the Videotex Recommendations referred to in clause 2. + +### 4.3.2 The VEMMI objects plane + +This plane receives VEMMI objects described in this Recommendation and their encoded data contents. The VEMMI objects plane shall be able to handle object overlapping and restoring mechanisms as referred to in 4.6 and 4.10.1. Within this plane, and for a given data content, the data rules and priorities as defined in the corresponding standards apply. + +## 4.4 Operation modes for VEMMI terminals + +Regardless of the current operation mode of the terminal, it shall always provide specific tools to manage the platform specific functions (disconnect, etc.). + +### 4.4.1 The standard mode + +This is the initial mode of operation of a VEMMI terminal when powered on or reset. + +In standard mode, the VEMMI terminal displays standard data in the standard plane. This standard datatype depends on the retrieval service to which the VEMMI terminal is connected. Standard data are fully visible. User inputs are not controlled by the VEMMI local manager. + +The terminal shall ignore all VEMMI commands except VEMMI\_Open or VEMMI\_Resume if the VEMMI session previously was suspended with a VEMMI\_Suspend. This command shall perform a switch to the VEMMI mode (VEMMI On/Off switches are then switched to the On position). + +### 4.4.2 The VEMMI mode + +In VEMMI mode, a VEMMI terminal can receive standard data and VEMMI objects data in two parallel paths, as shown in Figure 2. + +VEMMI object data are displayed in the VEMMI objects plane. Standard data are displayed in the standard plane. The display order for objects and for components within objects shall correspond to the ascending order of their CINs (component with the smallest CIN is displayed first). + +In VEMMI mode, the received standard data is used to update the standard data display memory. An update of the standard data window does not cause its activation. + +User inputs are controlled by the VEMMI local manager on the VEMMI window, which is the active window in this mode. + +![Block diagram of a possible VEMMI terminal structure showing data and control flows between various components.](4ee27dbf5ef12e7b58b0ef0937bc5a5e_img.jpg) + +The diagram illustrates the architecture of a VEMMI terminal, showing the flow of data and control signals between various components. + +**Legend:** + +- Data flows:** Represented by solid arrows. +- Controls:** Represented by hollow arrows. + +**Components and Connections:** + +- VEMMI local manager:** The central control unit, connected to all other components via control lines (hollow arrows). +- Protocols:** Connected to the VEMMI local manager and Layer 7 via bidirectional data flows (solid arrows with open heads). +- Layer 7 (Note):** Receives data from Protocols and sends it to the Standard data and VEMMI object data switcher. +- Standard data and VEMMI object data switcher:** Routes data between the VEMMI local manager, Protocols, and the Standard data decoder. +- Standard data decoder:** Receives standard data and outputs to the Standard data display memory and the VEMMI decoder. +- Standard data display memory:** Receives data from the decoder and outputs to the Standard data window. +- VEMMI decoder:** Receives data from the switcher and outputs to the VEMMI display memory. +- VEMMI display memory:** Receives data from the decoder and outputs to the VEMMI window. +- Standard data window:** Receives data from the Standard data display memory. +- VEMMI window:** Receives data from the VEMMI display memory. +- User interactions (keyboard, mouse ...):** Connected to the VEMMI local manager via control lines. +- Local storage:** Connected to the VEMMI local manager via control lines. +- Input focus and active window switch:** A switch that selects between the Standard data window and the VEMMI window based on control signals (VEMMI\_Open, VEMMI\_Resume, VEMMI\_Close, VEMMI\_Suspend). +- Input focus and active window:** The output of the switch, which is controlled by the VEMMI local manager. + +**Control Signals:** + +- VEMMI open/close, VEMMI suspend/resume:** Control signals from the VEMMI local manager to the Input focus and active window switch. +- VEMMI\_Open, VEMMI\_Resume:** Control signals from the VEMMI local manager to the VEMMI window. +- VEMMI\_Close, VEMMI\_Suspend:** Control signals from the VEMMI local manager to the Standard data window. + +**Reference:** T0824310-95/d02 + +Block diagram of a possible VEMMI terminal structure showing data and control flows between various components. + +NOTE – Standard protocols including Syntax-Based Videotex (SBV) based protocols or protocols amended for VEMMI mode as defined in clause 5. + +FIGURE 2/T.107 +Example of possible VEMMI terminal structure + +### 4.4.3 Switching between standard mode and VEMMI mode + +From the standard mode, a VEMMI terminal shall be switched to the VEMMI mode using the VEMMI\_Open or VEMMI\_Resume command. + +From the initial mode the terminal can be switched to the VEMMI mode using the VEMMI\_Open command. + +When a VEMMI\_Close command is received, the VEMMI terminal shall switch in the standard operation mode. + +The VEMMI\_Resume and the VEMMI\_Suspend command can be used to temporarily switch between the two modes. + +## 4.5 VEMMI elements data content + +The following content datatypes and attributes are defined within this Recommendation: + +- a) VEMMI high quality text; +- b) VEMMI bitmaps; +- c) colour. + +The following content datatypes and attributes are defined outside this Recommendation, but used as data content for VEMMI elements in this Recommendation: + +- a) Videotex data (as optional data content of the Graphic Output Area); +- b) bitmaps (JPEG, GIF, BMP); +- c) sound (WAVE, MIDI); +- d) graphical data; +- e) video data. + +It is mandatory for a VEMMI terminal to understand all commands related to the above mentioned data contents. + +No specific content datatype is mandatory to be used in a VEMMI application. However, in order to provide a satisfactory VEMMI service, a terminal should, as a minimum requirement, support the datatypes listed in Annex C. + +### 4.5.1 Text data definition + +Text Data are encoded in accordance with the ISO 8859-Series [13]. Depending on the terminal implementation, only a part of 8859-Series may be supported (see Annex B for 8859 mandatory subset of ISO 8859-Series). In addition, the host application can use the VEMMI\_Identify\_Term\_Cap command to enquire about the character sets supported in the terminal. A specific character set can be selected using the VEMMI\_Set\_Options command. This text data encoding is considered as the basic text encoding. When several character sets are used in the same application (multilingual application) the application can use the registered ISO appropriate designation escape sequences, as defined in ISO 2022 [10] and ISO 8859-Series [13] to switch between the different character sets. + +The following text data encodings can be used optionally: + +- ISO 10646-1 Unicode [15]; +- Recommendation T.51 [2] as given in Annex A; +- Recommendation T.52 [3]. + +For displaying window titles, menu choices and labels, the terminal application can use the local system font. For the application specific text-output, VEMMI offers enhanced capabilities. However, simple text based terminals can use the system font to display the high quality text. These terminals may then ignore the text attributes that they are not able to process and display text using the system font, in the available system colour, on the system background. + +Text data can be part of an object or component definition or it can be defined as a resource object. The following text attributes are specified: + +- text colour; +- text font; +- text height. + +The **text colour** defines the colour of the characters foreground. The character background is terminal specific. The **text font** is a set of characters with a particular, similar character design. In this context, an application can choose a font family, the specific font pertaining to this family is selected by the terminal application (in this Recommendation, by “font” a font family is meant). Table 1 presents the VEMMI font families: + +TABLE 1/T.107 +**VEMMI font families** + +| Font family | Font characteristics | Example | +|-------------|------------------------------|------------------------| +| SWISS | Proportional, without serifs | Helvetica, Switzerland | +| ROMAN | Proportional, with serifs | Times roman | +| FIXFONT | Monospaced | Courier | + +The fonts of these families should support variable sizes (scalable fonts). + +The **text height** specifies the height of the font. It is the height of the character cell, including a possible internal leading. The local manager shall insert additional space between adjacent text rows. The height is measured in points (1/72 inch). One point corresponds to 1/400 NDC. Italicized characters can be achieved with the attribute **Italic**. **Bold** increases the line thickness and **Underline** draws a line under each character. + +#### Example + +**SWISS, 10 points and bold** + +Roman, 8 points and underlined + +*Roman, 16 points, italic* + +**FIXFONT, 12 points, white** + +A combination of a font and a set of attributes is further named an attributed font and handled as a font resource object. It is referenced via the FIN (Font Identification Number). + +The following control characters should be used to format the text correctly: + +- SP, NBSP, SHY: see ISO 8859-1 [13]; +- CR, LF: see Recommendation T.50 [1]. + +To provide the “line feed” functionality within the text content of a component or a component item, the Carriage Return (CR) + Line Feed (LF) control characters given in Recommendation T.50 [1] shall be used. + +### 4.5.2 Bitmaps + +A bitmap is a pixel matrix containing either colour indices which point into the colour table, or Red Green Blue (RGB)-components. A bitmap can be referenced by an object or component and when it is instantiated by the terminals it appears as a rectangle with a colour pattern of the corresponding matrix of pixels. The definition is almost device-independent while the relationship between the bitmap bits and the pixels on the device is device specific. + +The bitmap is handled as a resource object and referenced by objects or components via the “Bitmap Identification Number” (BIN) which is unique in one application. Several bitmaps can be defined at a given point in time. + +### **4.5.3 Colour** + +The colour table provides a method for accessing the colour capabilities of the terminal device. It is assumed that the device can display at least 256 colours simultaneously. Because the device colour table is shared by more than one application, the UIs provide mechanisms (e.g. logical colour palettes) to support each application with its own table. This subclause defines the colour table for the VEMMI application. + +From the 256 colours, the User Interface (UI) reserves 20 colours for a system table. Therefore, the maximum number of colours for the VEMMI colour table is 236. In practice an application will use only a few numbers from these colours. The host application has the possibility to define the colour table by sending the RGB components. Objects, components or bitmaps can select these colours via indices. By default, 16 colour entries (0 to 15) are predefined. If the application uses a colour index > 15 which was not defined, the displayed colour is terminal dependent. + +Colour entries may be in use by other active applications in the terminals. This has to be managed by the local UI. + +Monochrome terminals support either two colour indices (e.g. black and white or the colour table loaded with shades of one colour). + +### **4.5.4 Videotex data** + +Data encoded in accordance with Annex B/T.101, Annex C/T.101 and Annex D/T.101 [4], for example: text, geometric. + +Data encoded in accordance with Annex E/T.101 [4], for audio data. + +Data encoded in accordance with Annex F/T.101 [4], for photographic data. + +The support of Videotex data is optional for a VEMMI terminal. + +The host application can inquire about the support of these data types using the VEMMI\_Identify\_Term\_Cap command. + +### **4.5.5 Sound** + +An application can embed references to sound sequences in objects. The terminal stores the sound in files. Upon a user action the sound is processed, possibly with an audio interface card. + +The two sound formats are suitable for: + +- wave devices (WAVE); +- Musical Instrument Digital Interface devices (MIDI). + +Sound can also be provided using the Videotex Audio syntax defined as Videotex data content (see 4.5.4.). + +### **4.5.6 Graphical data** + +Graphical data, such as lines, arcs, fill areas and the relevant drawing attributes are not directly supported by this Recommendation. However, an application can use VEMMI-integrated programmes (via operative objects), in which graphical drawing operations are performed. + +### **4.5.7 Video data** + +This Recommendation does not describe video data formats. But it provides the container (object) which can be used to embed moving video in VEMMI applications. + +## **4.6 VEMMI objects positioning and dimensioning** + +### **4.6.1 Positioning** + +The standard plane shall continue to support the coordinate system used at the underlying platform. + +The VEMMI objects plane shall support a Normalized Device Coordinate (NDC) system for positioning VEMMI objects and components within the DDA (see Figure 3). The normalized coordinates are theoretically expressed in the range 0;0 to 1;1. The 0;0 coordinate origin reference point represents the upper left-hand corner of the DDA, the 1;1 coordinate point represents the lower right-hand corner of a virtual square DDA with a side equal to the unit. For a non-square DDA, the unit is equal to the greatest side of the DDA. + +For typical display devices, using common 4:3 aspect ratio, the horizontal positioning is in the range 0 to 1 corresponding to the whole width of the DDA, the vertical positioning is in the range 0 to 0.75 corresponding to the whole height of the DDA. + +The origin reference point to position an object within the DDA is always the upper left corner of the DDA. The origin reference point to position a component within its parent object (container object) is also the upper left corner of a virtual DDA attached to the upper left corner of the object; that virtual DDA has exactly the same size as the standard DDA but with a position translation up to the object for positioning its own components. + +VEMMI items are generally implicitly positioned with respect to the width or the height of the nearest item on the left or above. + +![Diagram illustrating VEMMI positioning NDC space. It shows a hierarchy of coordinate systems: a large 'DDA (4:3)' rectangle with origin '0;0' at the top-left and '1;0' at the top-right; a 'Virtual DDA (4:3)' rectangle with origin '0;0' at the top-left and '1;0' at the top-right, positioned within the DDA; and a 'Unit square DDA' with origin '0;0' at the top-left and '1;1' at the bottom-right, positioned within the Virtual DDA. The diagram also shows a 'Dialogue box' containing a 'List' and three radio buttons, with its own 'Component origin reference point' at its top-left corner. Dimensions X and Y are indicated for the Dialogue box within the Virtual DDA.](9b9d2abd741ed4bafe7f78f89961c663_img.jpg) + +The diagram illustrates the VEMMI positioning NDC space. It shows a hierarchy of coordinate systems: + +- DDA (4:3)**: The outermost rectangle, representing the display device. Its origin reference point is at the top-left corner (0;0). The top-right corner is labeled 1;0. The bottom-left corner is labeled 0;0,75. The bottom-right corner is labeled 1;0,75. +- Virtual DDA (4:3)**: A smaller rectangle nested within the DDA. Its origin reference point is at the top-left corner (0;0). The top-right corner is labeled 1;0. The bottom-left corner is labeled 0;0,75. The bottom-right corner is labeled 1;0,75. +- Unit square DDA**: A rectangle nested within the Virtual DDA. Its origin reference point is at the top-left corner (0;0). The bottom-right corner is labeled 1;1. + +Inside the Unit square DDA, there is a **Dialogue box** containing a **List** and three radio buttons. The origin reference point for the Dialogue box is at its top-left corner. Dimensions **X** and **Y** are indicated for the Dialogue box within the Virtual DDA. + +T0815390-94/d03 + +Diagram illustrating VEMMI positioning NDC space. It shows a hierarchy of coordinate systems: a large 'DDA (4:3)' rectangle with origin '0;0' at the top-left and '1;0' at the top-right; a 'Virtual DDA (4:3)' rectangle with origin '0;0' at the top-left and '1;0' at the top-right, positioned within the DDA; and a 'Unit square DDA' with origin '0;0' at the top-left and '1;1' at the bottom-right, positioned within the Virtual DDA. The diagram also shows a 'Dialogue box' containing a 'List' and three radio buttons, with its own 'Component origin reference point' at its top-left corner. Dimensions X and Y are indicated for the Dialogue box within the Virtual DDA. + +FIGURE 3/T.107 +VEMMI positioning NDC space + +### 4.6.2 Dimensioning + +The standard plane shall continue to support the coordinate system used for dimensioning at the underlying platform. + +The VEMMI objects plane and VEMMI objects and components shall support a dimensioning system based NDC. + +The width and the height of a VEMMI object or of a VEMMI component, expressed in NDC, are referred with respect to their positioning reference point (upper left-hand corner), see Figure 4. + +In a VEMMI element, data content follows the rules for the coding of its relevant data syntax including a possible picture placement or positioning using the relevant coordinate system. + +![Diagram of the VEMMI positioning system showing nested coordinate systems and display areas.](2b3a967f6ce4f23649be995a353e39f8_img.jpg) + +The diagram illustrates the VEMMI positioning system with nested coordinate systems and display areas: + +- DDA (Display Data Area):** The outermost rectangle, defined by coordinates (0;0) at the top-left and (1;0) at the top-right, and (0;0,75) at the bottom-left and (1;0,75) at the bottom-right. Its origin is the **DDA origin reference point**. +- Object:** A smaller rectangle within the DDA, defined by coordinates (X 0;0) at its top-left and (Y) at its top-right. Its origin is the **Object origin reference point**. +- Component:** A rectangle within the object, defined by coordinates (x) at its bottom-left and (y) at its top-right. Its origin is the **Component origin reference point**. +- VTX DATA:** A rectangular area within the component, containing a computer monitor icon. +- Element display area:** A dashed rectangle that encompasses the VTX DATA and another icon (a printer or similar device) within the component. +- Virtual DDA:** A dashed rectangle that encompasses the entire element display area. A note states: "Virtual DDA used for element content (the positioning inside the virtual DDA shall follow the rules given with the specific content)". + +T0823550-95/d04 + +Diagram of the VEMMI positioning system showing nested coordinate systems and display areas. + +FIGURE 4/T.107 +VEMMI positioning system + +## 4.7 VEMMI elements states and state parameters + +### 4.7.1 Object + +An object can adopt different logical states with different state parameters. These states and state parameters may be the result of: + +- user inputs; +- local actions; +- actions taken by the VEMMI local manager; +- commands from the VEMMI application directly or via a metacode object. + +#### 4.7.1.1 Definition of object states + +Figure 5 shows the commands which can be used by the VEMMI application to change the object state or its state parameters. + +![State diagram for objects showing transitions between Referenced, Requested, Idle, Opened, Closed, and Stored states.](5445597cceefaca1ac89e710fe339325_img.jpg) + +``` + +stateDiagram-v2 + state Referenced + state Requested + state Idle + state Opened + state Closed + state Stored + + Referenced --> Requested : VEMMI_Object_Retransmission + Requested --> Opened : VEMMI_Create_Object + Idle --> Idle : VEMMI_Obj_Access Enable, VEMMI_Obj_Access Disable + Idle --> Opened : VEMMI_Destroy_Object, Local Action Destroy + Opened --> Idle : VEMMI_Create_Object + Opened --> Closed : VEMMI_Destroy_Object, Local Action Destroy, VEMMI_Destroy_Object, Local Destroy by the terminal because of a limitation of memory + Closed --> Idle : VEMMI_Destroy_Object, Local Action Destroy, VEMMI_Destroy_Object, Local Destroy by the terminal because of a limitation of memory + Opened --> Opened : VEMMI_Obj_Access Enable, VEMMI_Obj_Access Disable, VEMMI_Open_Object, Activation by the user, Deactivation by the user + Opened --> Closed : VEMMI_Close_Object, VEMMI_Close_All, Local Action Close Object + Closed --> Opened : VEMMI_Open_Application, VEMMI_Open_Object, Local Action Open Object + Closed --> Closed : VEMMI_Obj_Access Enable, VEMMI_Obj_Access Disable + Opened --> Stored : VEMMI_Store_Object, VEMMI_Open "autostore object", VEMMI_Close "autostore object" + Closed --> Stored : VEMMI_Store_Object, VEMMI_Open "autostore object", VEMMI_Close "autostore object" + Idle --> Stored : VEMMI_Erase_Object + Closed --> Idle : VEMMI_Create_Object "template" + +``` + +The diagram illustrates the state transitions for objects. The states are represented by ovals: Referenced, Requested, Idle, Opened, Closed, and Stored. Transitions are labeled with actions and local actions. + +- Referenced** to **Requested**: VEMMI\_Object\_Retransmission +- Requested** to **Opened**: VEMMI\_Create\_Object +- Idle** to **Idle**: VEMMI\_Obj\_Access Enable, VEMMI\_Obj\_Access Disable +- Idle** to **Opened**: VEMMI\_Destroy\_Object, Local Action Destroy +- Opened** to **Idle**: VEMMI\_Create\_Object +- Opened** to **Closed**: VEMMI\_Destroy\_Object, Local Action Destroy, VEMMI\_Destroy\_Object, Local Destroy by the terminal because of a limitation of memory +- Closed** to **Idle**: VEMMI\_Destroy\_Object, Local Action Destroy, VEMMI\_Destroy\_Object, Local Destroy by the terminal because of a limitation of memory +- Opened** to **Opened**: VEMMI\_Obj\_Access Enable, VEMMI\_Obj\_Access Disable, VEMMI\_Open\_Object, Activation by the user, Deactivation by the user +- Opened** to **Closed**: VEMMI\_Close\_Object, VEMMI\_Close\_All, Local Action Close Object +- Closed** to **Opened**: VEMMI\_Open\_Application, VEMMI\_Open\_Object, Local Action Open Object +- Closed** to **Closed**: VEMMI\_Obj\_Access Enable, VEMMI\_Obj\_Access Disable +- Opened** to **Stored**: VEMMI\_Store\_Object, VEMMI\_Open "autostore object", VEMMI\_Close "autostore object" +- Closed** to **Stored**: VEMMI\_Store\_Object, VEMMI\_Open "autostore object", VEMMI\_Close "autostore object" +- Idle** to **Stored**: VEMMI\_Erase\_Object +- Closed** to **Idle**: VEMMI\_Create\_Object "template" + +State diagram for objects showing transitions between Referenced, Requested, Idle, Opened, Closed, and Stored states. + +T0823870-95/d05 + +FIGURE 5/T.107 +State diagram for objects + +In general, the following logical states for objects are defined with certain restrictions applying to specific objects (see clause 7). + +##### - *Opened* + +An object which exists in the terminal is displayed. + +Opening an object is initiated by the VEMMI application, either as initial state at the time of the object creation, by a direct VEMMI command any time during the application or by a local action which is associated to a component and triggered by user interaction. + +##### - *Closed* + +An object which exists in the terminal is not displayed. + +Closing an object is initiated by the VEMMI application, either as initial state at the time of the object creation, by a command any time during the application or by a local action which is associated to a component and triggered by user interaction. + +##### - *Referenced* + +An object which does not exist on the terminal was referenced by a VEMMI\_Open\_Object command or the local action “Open object”. The terminal shall request the retransmission of the specified object with the VEMMI\_Object\_Retransmission command. + +##### - *Requested* + +After the attempt to open a non-existing object, a request for object retransmission shall be sent from the terminal to the VEMMI application. While the terminal is waiting for the creation of the requested object, the object is in the requested state. + +##### - *Stored* + +A copy of an object (including all its components), which was used in an earlier session or in the actual opened session and has been stored permanently in the terminal (e.g. on hard disk). + +A stored object shall implicitly have the state closed. Stored objects are made available for object operations with the command Open Application. Then they behave like received closed objects. + +If an object that was previously stored in the terminal is requested to be stored again by the host application, the newer one shall replace the older one with all its parameters and states. + +Stored objects can be deleted with the command VEMMI\_Erase\_Objects. + +An object which is in the closed state may be destroyed from terminal memory by a local decision of the VEMMI local manager (e.g. because of a limitation of memory). The VEMMI application may be informed about this local destroy using the VEMMI error command “Object Destroy Indication”. If the terminal receives a VEMMI\_Open\_Object command referring to an object that has been destroyed or if a local action “Open object” referring to a destroyed object is executed, the terminal shall request the retransmission of the object from the application, using the VEMMI\_Object\_Retransmission command. The VEMMI application shall then create the requested object again using the VEMMI\_Create\_Object command applying its current state and its current state parameters within the VEMMI application. A VEMMI\_Create\_Object command resulting from a VEMMI\_Object\_Retransmission request shall always create the object in the open state. + +#### **4.7.1.2 Definition of object state parameters** + +In general, the following state parameters for objects are defined with certain restrictions applying to specific objects (see clause 7). + +##### - *Active* + +An object currently has the input focus. The user inputs always refer to the active object. The active object is on top of the DDA. If the active object is inaccessible it is not possible for the user to interact with it. + +The active state management is described in 4.10.1. + +##### - *Inactive* + +The opposite of active. + +- *Accessible* + +The user can interact with the object. + +Enabling the interaction with an object is initiated by the VEMMI application, either as initial state at the time of the object creation, by a VEMMI command any time during the application or by a local action which is associated to a component and triggered by user interaction. + +- *Inaccessible* + +The opposite of accessible. + +The active/inactive state parameter applies only to components which are in the opened state. The accessible/inaccessible state parameter is applicable to open and closed components. Any combination of the state parameters active/inactive and accessible/inaccessible can exist for an open component. + +### 4.7.2 Component + +#### 4.7.2.1 Definition of component states + +A component can adopt different logical states with different state parameters. These states and state parameters may be the result of: + +- user inputs; +- local actions; +- commands from the VEMMI application. + +Figure 6 shows the possible states for components. The states and state parameters of components can be changed during the applications using the VEMMI\_Modify\_Component command. + +![State diagram for components showing Opened and Closed states with transitions and associated actions.](2834bdd6eb8540277e609decbb924003_img.jpg) + +``` + +graph LR + Opened([Opened]) -- Open --> Closed([Closed]) + Closed -- Close --> Opened + Opened --> Opened + Closed --> Closed + +``` + +The diagram illustrates the state transitions for components. It features two main states: **Opened** and **Closed**, each represented by an oval. Transitions between these states are labeled **Open** (from Opened to Closed) and **Close** (from Closed to Opened). Both states have self-loop arrows. Below the **Opened** state, a list of actions is provided: **Access enable**, **Access disable**, **Activation by the user**, and **Deactivation by the user**. Similarly, below the **Closed** state, the actions **Access enable** and **Access disable** are listed. The identifier **T0815470-94/d06** is located to the right of the **Closed** state. + +State diagram for components showing Opened and Closed states with transitions and associated actions. + +FIGURE 6/T.107 +State diagram for components + +In general, the following logical states for components are defined with certain restriction applying to specific components (see clause 7). + +- *Opened* + +A component which exists within an object is displayed. + +Opening a component is initiated by the VEMMI application, either as initial state at the time of the object creation, by a VEMMI\_Modify\_Component command any time during the application or by a local action which is associated to a component and triggered by user interaction. + +- *Closed* + +A component which exists in the terminal is not displayed. + +Closing a component is initiated by the VEMMI application, either as initial state at the time of the object creation, by a VEMMI\_Modify\_Component command any time during the application or by a local action which is associated to a component and triggered by user interaction. + +#### 4.7.2.2 Definition of component state parameters + +In general, the following state parameters for components are defined with certain restrictions applying to specific components (see Clause 7). + +##### - *Active* + +A component has currently the input focus. The user input always refers to the active component within the active object. If the active component is inaccessible, it is not possible for the user to interact with it. + +The active state management is described in 4.10.1. + +##### - *Inactive* + +The opposite of active. + +##### - *Accessible* + +The user can interact with the component if it is part of the current active object. + +Enabling the user interaction with a component is initiated by the VEMMI application, either as initial state at the time of the object creation, by a VEMMI\_Modify\_Component command any time during the application or by a local action which is associated to a component and triggered by user interaction. + +##### - *Inaccessible* + +The opposite of accessible. + +## 4.8 Local action management + +VEMMI commands are generally issued by the VEMMI application to change the state or the state parameters of an object or component. Only a very limited number of changes or object or component states or their parameters can be initiated by the terminal. + +To enable the VEMMI application to interact with the user, the terminal shall provide the capability to report the user inputs on the access or validation of components. + +The result of these interactions is that changes of object or component states, which are the result of user inputs, could be delayed because the user inputs were sent to the VEMMI application first and then the application could react with a VEMMI command to change the state. This procedure might cause unacceptable response times on data links with lower data throughput. To improve the response times, a set of local actions has been defined. + +Local actions are part of the component definitions and stored in the terminal at the time of the object creation. Each local action can consist of a list of “Element specific commands”, a list of “Report commands” and a list of “General commands” in any order. The following commands are defined: + +### - a) *Element specific commands* + +- open components of the parent object (parameter: list of CINs); +- close components of the parent object (parameter: list of CINs); +- open objects (parameter: list of OINs); +- close objects (parameter: list of OINs); +- change components state parameter of a component in the parent object to inaccessible (parameter: list of CINs); +- change components state parameter of a component in the parent object to accessible (parameter: list of CINs); +- destroy objects (parameter: list of OINs); +- open blocking object (parameter: OIN). + +### - b) *Report commands* + +- report OIN, CIN; +- report the current values of the component; + +- report the values of all components in the parent object; +- report all values of all components in the parent objects that have changed (also via a VEMMI\_Modify\_component) since the last report or since the object creation if this is the first report. + +### c) *General commands* + +- user lock; +- restore initial values of all input components in the parent object. This command should only be applied if the object was created with the “StoreInitialValue” attribute set true. + +These commands are part of the object definition and they can appear in the local action of a component in any possible order. The order of appearance shall be equal to the order of their execution. There are two specific trigger events which induce the performance of local actions: + +- activation of a component; +- validation of a component. + +A list of “Element specific commands”, a list of “Report commands” and a list of “General commands” can be used to specify one local action for a component. No command of a specific type is mandatory for a local action. + +There are two specific trigger events which induce the performance of local actions: + +- activation of a component; +- validation of a component. + +A local action can be associated to each of these trigger events. + +## 4.9 Memory considerations + +VEMMI terminals are supposed to have memory capabilities correctly dimensioned to provide a satisfactory VEMMI service in close relationship with their data type contents handling. + +When there is not enough memory to execute a VEMMI command or a local action, the local manager may decide to destroy some closed objects. This mechanism is terminal dependent. + +The VEMMI terminal shall send a VEMMI\_Error (Out of memory) message to the VEMMI application when it does not have the possibility to release enough memory to process a received object description with a VEMMI\_Create\_Object command, VEMMI\_Modify\_Component command or VEMMI\_Open\_Object command. In that case it may ignore further VEMMI\_Create\_Object commands as long as the VEMMI application has not released a significant part of memory using VEMMI\_Close\_Object or VEMMI\_Destroy\_Object commands. The VEMMI application may also decide to disconnect the line if the application cannot be performed correctly due to a lack of memory in the terminal; however, the user shall always be informed of that decision by means of a message in a Message Box. + +## 4.10 Common rules for object handling + +### 4.10.1 Active state and focus management + +A VEMMI object can become active as the result of: + +- a) opening by the VEMMI application; +- b) user access; +- c) a local action with the element specific command “open object”; +- d) closing the active object. The open object that was most recently active becomes the new active object. + +The active state shall be given to the last opened VEMMI object up to a user access to a different opened VEMMI object. When an accessible opened VEMMI object is accessed by the user, the active state shall be given to this VEMMI object by the local manager. The active state is then handled by the local manager up to a new VEMMI object opening or re-opening action from the VEMMI application. There should always be one single active object on the DDA. The active object can be inaccessible. + +If objects use a common area on the DDA, the successive object activation leads to partial or full object overlapping. The active object shall always be fully visible to the user just after its activation. The previous active object is logically just beneath the active object. This rule shall apply to all previously active objects. + +When set active, the VEMMI object and/or one of its components shall receive its focus from the local manager. The active state of the VEMMI object and/or of the VEMMI components shall be clearly visually indicated to the user. Within the active VEMMI object, not more than one accessible VEMMI component shall receive the active state and the focus. + +The first time an object is displayed and consequently activated, the component which gets the focus may be specified by the VEMMI application within the object description. If there is no component specified or the component specified is not opened, then the terminal shall give the focus to the first created opened and accessible component. The other times the manner of giving the focus on activation of an object to one of its components is terminal dependent (same rule as above, memorization of the last accessed component, the nearest component of the user access to the parent object). + +### **4.10.2 Behaviour of the modal mode** + +For a modal active object any user interaction with another VEMMI object of the same VEMMI application is forbidden by the terminal, any tentative attempt is indicated to the user (buzzer). + +All the commands received from the host and all the local actions resulting from user interactions with the components of the modal object are executed. + +### **4.10.3 Size considerations and clipping** + +The data content of a VEMMI element shall be sent with dimensions and a possible position compatible with the size description of its container (object or component). A VEMMI terminal shall clip non-consistent data content to the overall dimensions of the container. + +For bitmap data content specific rules apply that are given with the description of the elements. + +## **4.11 Local object storage** + +A host application has the possibility to request the load of objects locally stored in the terminal. Such a set of objects is application specific and contains typically those parts which remain unchanged for a longer time period and it is therefore more efficient not to transmit them in each dialogue session to the terminal. The loaded objects are processed in the same way as if they were received during the present session. Upon a host request they can be restored again in order to keep them up to date. The objects storage does not imply a removal of the objects from the terminal application, only a copy of the objects is stored. The dialogue may continue and is not affected by the objects storage. An object set is identified with the application identifier. + +The timestamp is received from the host at the beginning of the application. It is stored with the objects and reused in later sessions. The timestamp value is never calculated by the terminal, it is only used in comparison to find outdated objects. Whenever an object is stored locally in the terminal it shall have a timestamp associated. The value of this timestamp shall be determined as follows: + +- if the object was created by the host (by VEMMI\_Create\_Object) during the current session or if any component of the object was modified (by VEMMI\_Modify\_Component) during the current session, the object shall be stored with the timestamp value given by the VEMMI\_Open\_Application command for the current application; +- in all other cases the objects timestamp shall remain unchanged. (The object was loaded without change from the local storage during this session.) + +Two attributes which are part of the object definition can be used additionally to request the object storage either immediately after the object creation (template) or at the end of the application (autostore). + +A stored set of objects contains the following: + +- the application identifier; +- the objects including their components and the associated timestamp; + +- the referenced files (if a referenced file is not available in the terminal, the object is considered incomplete and shall not be stored); +- the relevant loaded colour table. + +The storage format is terminal specific because the objects are loaded and stored only by the same terminal. + +The terminal implementation should provide the user with the appropriate means to manage the local storage and typically the user may limit its maximum size. + +## 4.12 Symbolic directory names + +In order to support the host application to locate the correct files, symbolic directory names are defined. They can be used as part of the “filename” parameter. The terminal maps them on real directory respective filenames. In the following example, a host application uses a symbolic directory name to identify a bitmap file: + +VEMMI\_Create\_Object (OIN = 7, ..., filename = “\$CD\ARTISTS\DANCER\LISA.BMP”, pict file type = BMP). + +The string “\$CD” identifies the CD-ROM drive. The terminal substitutes this symbolic name with the real drive identification. The complete file identification might be: “H:\ARTISTS\DANCER\LISA.BMP”. + +The following symbolic names are defined, the application may use other symbolic names: + +| Name | Meaning | +|-------|-------------------------------------------------------------| +| \$APL | Parent directory of the applications stored in the terminal | +| \$FTD | Parent directory of downloaded files | +| \$CD | Drive directory name of a CD-ROM drive | + +These symbolic names can be used in the parameter “filename” of the VEMMI commands. The symbolic name shall appear only once in the filename parameter. For the separation of the symbolic name from additional subdirectories and from the filename, the character “\”, code 5/12, should be used. + +## 4.13 Specific rules for dedicated terminals + +All service primitives including their parameters shall be understood also by a dedicated terminal. Regarding the execution of the commands related to specific functionality, a dedicated terminal may apply graceful degradation mechanisms. + +The following functionality can be gracefully degraded by a dedicated terminal: + +- colour definition; +- in-text attributes (fonts, colours, font attributes); +- local storage; +- NDC-positioning and dimensioning. + +For dedicated VEMMI terminals only able to handle Videotex data contents on a character basis (alphamosaic, DRCS, Photographic Profile 1), VEMMI objects and components can be physically positioned and dimensioned to the nearest corresponding display character position. Consequently, to avoid side effects between VEMMI objects, NDC object positions should be expressed in a direct multiple of character positions for VEMMI application using only this type of Videotex data contents. + +For dedicated VEMMI terminals only able to handle Videotex data contents on a character basis, VEMMI can be used with 80-character mode making use of the appropriate SWITCHING SEQUENCE or the DEFINE FORMAT Videotex Presentation Data Element (VPDE) to switch to the desired Data Syntax. Eighty-character mode is not mandatory for a VEMMI terminal. + +Dedicated VEMMI terminals shall recognize, but not necessarily process the whole or part of the VEMMI high quality text attributes they are not able to display. These terminals may then ignore the text attributes and display text using the system font, in the available system colour, on the system background. + +Dedicated VEMMI terminals shall support the different kinds of VEMMI objects, with possible restrictions applying to the operative objects. As a file management system is not mandatory, they can manage the files they receive in the VEMMI\_Resource\_Transfer command in their own internal representation. + +Dedicated terminal should support the minimum kernel datatypes defined in Annex C. However, when used in a retrieval service where the standard mode is the Videotex mode and when the terminal does not support the Videotex photographic syntax (to be enquired using the TFI) the support of JPEG and GIF is not mandatory. When the terminal supports the Videotex photographic syntax the support of JPEG is mandatory; the support of GIF is recommended. In the same service conditions, when a terminal does not support the Videotex audio syntax the support of WAVE and MIDI is not mandatory. When the terminal supports the Videotex audio syntax the support of WAVE is mandatory; the support of MIDI is recommended. + +Dedicated terminals need not support the stretching of bitmap data to fill the element display area. If the presentation attribute for a bitmap is set to “stretched”, the terminal may present the bitmap tiled. + +# 5 Service description + +This clause describes the service characteristics offered by the VEMMI. + +The service is defined between a terminal and a remote application. No assumption is made about the way the terminal accesses to the service (Public Switched Telephone Network (PSTN)/Packet Switched Public Data Network (PSPDN)/Integrated Services Digital Network (ISDN)) and the way the connection is established. + +All VEMMI service elements or VEMMI commands shall only be issued on an established network connection. Before sending the first VEMMI command, the VEMMI application should issue a Terminal Facility Identifier (TFI) request to ensure that the terminal is able to support the VEMMI standard. + +All VEMMI service elements are mandatory for a VEMMI terminal. A VEMMI terminal shall understand all VEMMI service elements including all their parameters. + +The VEMMI services are divided into two groups: + +- services initiated by the VEMMI application; +- services initiated by the VEMMI terminal. + +A second source of commands for a VEMMI terminal is the metacode object. See Table 2. + +The following services are confirmed explicitly: + +- VEMMI\_Identify\_Term\_Cap is confirmed with VEMMI\_Identify\_Term\_Cap\_Resp; +- VEMMI\_Open\_Application is confirmed with VEMMI\_Open\_Application\_Resp; +- VEMMI\_Store\_Objects is confirmed with VEMMI\_Store\_Objects\_Resp. + +There is no explicit confirmation in any other of the service elements. + +All VEMMI services, except VEMMI\_Open\_Object, which refer to a non-existing object shall be ignored by the VEMMI terminal. If a VEMMI\_Open\_Object refers to a non-existing object, the terminal shall request its retransmission. + +NOTE – In the following subclause, all VEMMI services are described but only those parameters are listed which are necessary to understand the service. For a complete parameter list, see clause 8. + +TABLE 2/T.107 + +## **VEMMI services** + +| VEMMI Services | Initiated Application/Terminal | Function | +|-------------------------------|--------------------------------|--------------------------------------------------------| +| VEMMI_Set_Translation_Mode | Application/Terminal | Sets the translation mode for VEMMI data | +| VEMMI_Open | Application | Switch to VEMMI mode and reset | +| VEMMI_Close | Application | Switch to standard mode and reset | +| VEMMI_Suspend | Application | Switch to standard mode | +| VEMMI_Resume | Application | Switch to VEMMI mode | +| VEMMI_Identify_Term_Cap | Application | Request for terminal capabilities | +| VEMMI_Identify_Term_Cap_Resp | Terminal | Response to the “identify terminal capability” request | +| VEMMI_Set_Options | Application | Set options in the terminal | +| VEMMI_Create_Object | Application | Object definition | +| VEMMI_Open_Object | Application | Display object | +| VEMMI_Open_Blocking_Object | Application | Open object | +| VEMMI_Close_Object | Application | Clear an object from the screen | +| VEMMI_Close_All | Application | Clear all the objects from the screen | +| VEMMI_Destroy_Object | Application | Clear object in the terminal memory | +| VEMMI_Obj_Access_Disable | Application | User access is not permitted | +| VEMMI_Obj_Access_Enable | Application | User access is permitted | +| VEMMI_Modify_Component | Application | Modify components characteristics | +| VEMMI_Obj_Location_Change | Application | Defines a new object position | +| VEMMI_Load_Col_Table | Application | Loads a colour table | +| VEMMI_Reset_Col_Table | Application | Resets a colour table | +| VEMMI_Open_Application | Application | Opens an application | +| VEMMI_Open_Application_Resp | Terminal | Response to “open application” request | +| VEMMI_Delete_Outdated_Objects | Application | Deletes outdated objects | +| VEMMI_Store_Objects | Application | Stores a set of objects | +| VEMMI_Store_Objects_Resp | Terminal | Response to a “store object” request | +| VEMMI_Erase_Objects | Application | Delete objects from the local storage | +| VEMMI_User_Lock | Application | User inputs are not permitted | +| VEMMI_User_Unlock | Application | User inputs are permitted | +| VEMMI_Object_Retransmission | Terminal | Request for object retransmission | +| VEMMI_User_Data | Terminal | User data in VEMMI mode | +| VEMMI_Error | Terminal | Error condition or situation | +| VEMMI_Resource_Transfer | Application | Resource transfer | +| VEMMI_Resource_Transfer_Abort | Terminal | Resource transfer abort | + +## 5.1 Service elements initiated by the VEMMI application and the terminal + +If issued by the VEMMI application, this service element shall be used to indicate that the VEMMI data sent from the application to the terminal are transcoded using a specified translation mode. + +If issued by the VEMMI terminal, this service element shall be used to indicate that the VEMMI data sent from the terminal to the application are transcoded using a specified translation mode. + +Since a VEMMI terminal usually begins operation, by default, in either a 7-or 8-bit environment it shall not be mandatory for a VEMMI application to be sent as a first VEMMI command in a VEMMI session a VEMMI\_Set\_Translation\_Mode to switch the terminal to a desired translation mode. If the application cannot be sure that all terminals that are connecting operate in a specific environment, it should send a VEMMI\_Set\_Translation\_Mode to ensure that the terminal will interpret the VEMMI commands correctly. See Table 3. + +Typically the VEMMI\_Set\_Translation\_Mode is the first VEMMI command of a VEMMI session but it can be used at any time during a VEMMI session. + +NOTE – The translation mode can be different in both directions. + +TABLE 3/T.107 + +### Parameters + +| Parameters | Description | +|-----------------|--------------------------------------------------| +| TranslationMode | One byte specifying the desired translation mode | + +The TranslationMode parameter can have the following values: + +- 2/0: no translation (transparent); +- 2/1: 3 in 4 encoding (see Recommendation T.101 [4]); +- 2/2: 7-shift encoding (see Recommendation T.101 [4]). + +## 5.2 Service elements initiated by the VEMMI application + +### 5.2.1 VEMMI\_Open + +This service element shall be used to switch the VEMMI terminal to the VEMMI operation mode. The switching mechanism is defined in 4.4.3. In VEMMI operation mode, the mechanism described in 4.4.2 shall apply. + +In addition to the switch to VEMMI operation mode, the service element shall perform the following resets: + +- close an open application; +- destroy all objects from the set of objects that are in the “opened” or “closed” state; +- all opened objects are cleared from the display; +- release all identification numbers for resource objects; +- set the colour table to the predefined values. + +Objects stored in a local storage are not affected. + +If this command is received in the VEMMI mode, no switch is necessary but only the resets are performed. See Table 4. + +TABLE 4/T.107 + +#### **Parameters** + +| Parameters | Description | +|-------------|-------------------------------------------------------------------------------------------------------------------------------| +| Version | Identifier of the VEMMI version | +| PrivateMode | Private parameter which can be used in some “page-based” Videotex services. This mode is not described in this Recommendation | + +### 5.2.2 VEMMI\_Close + +This service element shall be used to switch the VEMMI terminal to the standard mode. The switching mechanism is defined in 4.4.3. In standard operation mode, the mechanism described in 4.4.1 shall apply. + +In addition to the switch to standard mode, the service element shall perform the resets defined in 5.2.1. See Table 5. + +TABLE 5/T.107 + +#### **Parameters** + +| Parameters | Description | +|------------|-------------| +| None | | + +### 5.2.3 VEMMI\_Resume + +This service element shall be used to switch the VEMMI terminal to the VEMMI operation mode. The parameters of this service element are the same as for the VEMMI\_Open (see 5.2.1). With this service element no reset shall be performed. See Table 6. + +TABLE 6/T.107 + +#### **Parameters** + +| Parameters | Description | +|-------------|-------------------------------------------------------------------------------------------------------------------------------| +| Version | Identifier of the VEMMI version | +| PrivateMode | Private parameter which can be used in some “page-based” Videotex services. This mode is not described in this Recommendation | + +### 5.2.4 VEMMI\_Suspend + +This service element shall be used to switch the VEMMI terminal to the standard mode. No reset shall be performed. See Table 7. + +TABLE 7/T.107 + +#### **Parameters** + +| Parameters | Description | +|------------|-------------| +| None | | + +### **5.2.5 VEMMI\_Identify\_Term\_Cap** + +This service element shall be used to request identification of the capabilities of the terminal. See Table 8. + +The following information can be obtained: + +- VEMMI version identification; +- local storage support (supported/not supported); +- list of preferred user languages (string); +- system type (e.g. IBM compatible, Macintosh, ...), operating system (e.g. MS-DOS, OS2, Microsoft Windows, ...), operating system version (e.g. 3.1, ...) (string); +- a list of supported datatypes (reference to the VEMMI content encoding identification catalogue). + +If the DesiredInformation parameter is not present, the terminal shall respond giving a complete list that identifies all its capabilities. + +TABLE 8/T.107 + +#### **Parameters** + +| Parameters | Description | +|--------------------|-------------------------------------------------------------| +| DesiredInformation | The type of information that is requested from the terminal | + +### **5.2.6 VEMMI\_Set\_Options** + +This service element shall be used to set options in the terminal. See Table 9. + +The following options can be set: + +- if the terminal supports different kinds of text encoding, the desired encoding standard can be selected. + +TABLE 9/T.107 + +#### **Parameters** + +| Parameters | Description | +|--------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| TextStandard | Reference to a text encoding standard in the VEMMI content encoding identification catalogue which shall be used at the beginning of the encoding of datatypes string and character | + +### 5.2.7 VEMMI\_Create\_Object + +This service element shall be used to define a VEMMI object and its components in the VEMMI terminal. The VEMMI terminal shall create the object and shall apply the object state and state parameters given in its definition. + +OINs shall be unique at one time in an application. The creation of an object with an already existing OIN shall cause the destruction of the previously defined object. + +CINs shall be unique within an object. The definition of a component with an already existing CIN shall cause the destruction of the previously defined component. See Table 10. + +TABLE 10/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|----------------------------------------------------------------------------------------------------------------------------------| +| Object Identification Number | | +| Template | If an application is open the object shall be stored immediately after creation | +| Autostore | If an application is open the object shall be stored at the reception of a VEMMI_Open, a VEMMI_Close or a VEMMI_Open_Application | + +### 5.2.8 VEMMI\_Open\_Object + +This service element shall be used to set an object to the opened state in the VEMMI terminal. The terminal shall display the specified object immediately. If the object is not present in the terminal, it shall request the object by sending a VEMMI\_Object\_Retransmission request to the VEMMI application with the specified OIN, in this case “Rule A” as described in 5.3.2. shall be used. The application shall then create the object again, applying its current state and state parameters. + +A VEMMI\_Open\_Object command referring to an already opened object causes the activation of the object. + +If a VEMMI\_Open\_Object is applied to a resource object, the terminal shall verify whether the object is available. If not, it shall be requested. No further action shall be performed. + +If a VEMMI\_Open\_Object is applied to a metacode object, the terminal executes the object content. If not present it shall be requested. + +If a VEMMI\_Open\_Object is applied to an operative object, the terminal executes the program. If not present it shall be requested. See Table 11. + +TABLE 11/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +### 5.2.9 VEMMI\_Open\_Blocking\_Object + +This service element performs the same as VEMMI\_Open\_Object except that the retransmission case “Rule B” as described in 5.3.2. shall be used. + +### 5.2.10 VEMMI\_Close\_Object + +This service element shall be used to close a VEMMI object in the VEMMI terminal. The VEMMI terminal shall clear the indicated object from the screen but keep it in its memory. The current state parameters and values of the components shall not be changed. + +When receiving a VEMMI\_Close\_Object indication referring to an active object, the new active object in the VEMMI terminal shall be the opened object that was most recently active in the terminal. + +For objects that are not displayable or are already in a closed state, the VEMMI\_Close\_Object has no effect. See Table 12. + +TABLE 12/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +### 5.2.11 VEMMI\_Close\_All + +This service element shall be used to close all the VEMMI objects in the VEMMI terminal. A VEMMI\_Close\_All service element shall not change the current operation mode of the terminal. See Table 13. + +TABLE 13/T.107 + +#### Parameters + +| Parameters | Description | +|------------|-------------| +| None | | + +### 5.2.12 VEMMI\_Destroy\_Object + +This service element shall be used to remove a VEMMI object from a set of objects that are in the state “opened” or “closed”. The terminal shall remove all data belonging to this object from its memory. If the VEMMI\_Destroy\_Object is applied on an opened object, it shall be closed by the local manager and then destroyed. If the object was active, the new active object in the VEMMI terminal shall be the opened object that was most recently active in the terminal. See Table 14. + +TABLE 14/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +### 5.2.13 VEMMI\_Obj\_Access\_Disable + +This service element shall be used to restrict the user access to an object in the VEMMI terminal. The access shall be restricted until a VEMMI\_Obj\_Access\_Enable service element referring to the same object is received by the VEMMI terminal. + +If the object was active, the new active object shall be the open object that was most recently active in the terminal. A VEMMI\_Obj\_Access\_Disable Indication referring to an active object shall interrupt the user interaction with this object. See Table 15. + +TABLE 15/T.107 + +#### **Parameters** + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +### 5.2.14 VEMMI\_Obj\_Access\_Enable + +This service element shall be used to permit user access to an object in the VEMMI terminal. The access shall be permitted until a VEMMI\_Obj\_Access\_Disable service element referring to the same object is received by the VEMMI terminal. + +A VEMMI\_Obj\_Access\_Enable Indication received in the VEMMI terminal and referring to an inactive object shall not change this state parameter. See Table 16. + +TABLE 16/T.107 + +#### **Parameters** + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +### 5.2.15 VEMMI\_Modify\_Component + +This service element shall be used to modify one or several VEMMI components belonging to a VEMMI object created into the VEMMI terminal. The possible modifications in VEMMI components are defined in the component definition tables of 9.6. + +If a VEMMI\_Modify\_Component command is applied to an opened object, it shall have an immediate visual effect in the VEMMI terminal if the modified part is visible. + +A VEMMI\_Modify\_Component command shall not change the active/inactive state parameter of the object in the VEMMI terminal. See Table 17. + +TABLE 17/T.107 + +#### **Parameters** + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | +| Modification description | | + +### 5.2.16 VEMMI\_Obj\_Location\_Change + +This service element shall be used only to change the position of a VEMMI object (not component) in the VEMMI, terminal screen. If a VEMMI\_Obj\_Location\_Change command is referring to a VEMMI closed object no visible effects shall be encountered. This service element shall not change the active/inactive state parameter of an object. + +A VEMMI\_Obj\_Location\_Change service element shall never be applied to an Application Bar. See Table 18. + +TABLE 18/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------------------| +| Object Identification Number | | +| XPos | New horizontal position | +| YPos | New vertical position | + +### 5.2.17 VEMMI\_Load\_Col\_Table + +This service element shall be used by the host to define colours in the colour table. + +The colours are defined consecutively, started with the index “ColEntry”. The terminal shall send an error message to the host if the requested colours cannot be defined, e.g. because the device supports less colours than the host requested. See Table 19. + +TABLE 19/T.107 + +#### Parameters + +| Parameters | Description | +|------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| ColEntry | Colour index from which the colours are defined in ascending order | +| ColRGBList | The list consists of triplets which give the red, green and blue component of a colour. Each component value is in the range 0 .. 63. The value 0 means no intensity for the component, the value 63 means maximum intensity | + +NOTE – If this service is not supported by the terminal, this shall be reported to the using application using the VEMMI\_Error “Service not supported”. + +### 5.2.18 VEMMI\_Reset\_Col\_Table + +This service element shall be used by the host to reset all previously defined colours. This command has no parameters. Only the default colours (indices 0 .. 15) remain defined. If the default colours have been redefined with VEMMI\_Load\_Col\_Table, this command sets the default colours to their predefined values. See Table 20. + +TABLE 20/T.107 + +#### Parameters + +| Parameters | Description | +|------------|-------------| +| None | | + +The default colours are given in Table 21. + +TABLE 21/T.107 + +#### Parameters + +| Colour index | Red | Green | Blue | Colour | +|--------------|-----|-------|------|---------------| +| 0 | 0 | 0 | 0 | Black | +| 1 | 0 | 0 | 42 | Blue | +| 2 | 0 | 42 | 0 | Green | +| 3 | 0 | 42 | 42 | Cyan | +| 4 | 42 | 0 | 0 | Red | +| 5 | 42 | 0 | 42 | Magenta | +| 6 | 42 | 21 | 0 | Brown | +| 7 | 42 | 42 | 42 | White | +| 8 | 21 | 21 | 21 | Grey | +| 9 | 21 | 21 | 63 | Light blue | +| 10 | 21 | 63 | 21 | Light green | +| 11 | 21 | 63 | 63 | Light cyan | +| 12 | 63 | 21 | 21 | Light red | +| 13 | 63 | 21 | 63 | Light magenta | +| 14 | 63 | 63 | 21 | Yellow | +| 15 | 63 | 63 | 63 | Bright white | + +NOTE – If this service is not supported by the terminal, this shall be reported to the using application using the VEMMI\_Error “Service not supported”. + +### 5.2.19 VEMMI\_Open\_Application + +This service element shall be used by the host to load a set of objects and to define the name and attributes of the current application. Additional support can be provided using symbolic directory names as described in 4.12. Locally stored object sets are identified by the application identifier. A timestamp is used to associate version information with the objects of this application. See Table 22. + +TABLE 22/T.107 + +#### Parameters + +| Parameters | Description | +|-------------|------------------------------------------------------------| +| ApplId | String with the application name | +| ApplAddData | Additional application identification data | +| Timestamp | Time in seconds since 1.01.1970, Greenwich Mean Time (GMT) | + +The parameter ApplId shall contain the application name. Additional information, like name of the company or the organization to which the application belongs or the author of the application can be given with the parameter ApplAddData, which is not mandatory. The terminal does not need to analyze the content of ApplId, it is only used to identify the requested application. + +Application providers should take care to choose unique application identifiers, in order to avoid overwriting of other applications. + +### 5.2.20 VEMMI\_Delete\_Outdated\_Objects + +This service element shall be used by the host to request the deletion of outdated local objects of the current application from the terminal storage. See Table 23. + +If the host issues a VEMMI\_Delete\_Outdated\_Objects with the timestamp requirements for specific objects, the terminal shall react as follows: + +- if an object is referenced with a timestamp value higher than the timestamp value of the locally stored object, this object shall be deleted from the local storage. The host application can thus be certain that outdated objects are no longer used. + +TABLE 23/T.107 + +#### Parameters + +| Parameters | Description | +|------------|----------------------------------------------------------------------------------------| +| UpdateList | This parameter contains groups, each of two elements, a timestamp and a set of objects | + +In order to update an application partially, this command is typically sent following a VEMMI\_Open\_Application. + +### 5.2.21 VEMMI\_Store\_Objects + +This service element shall be used by the host to request the terminal to store the current loaded objects or a part of them. The timestamp of the current open application, supplied with the VEMMI\_Open\_Application command, is associated to each object. See Table 24. + +TABLE 24/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +If the parameter is absent, all currently loaded objects are stored. + +### 5.2.22 VEMMI\_Erase\_Objects + +This service element shall be used by the host to request the deletion of objects of the current application from the local storage of a terminal. To increase security implementation, the VEMMI terminal could ask the user before executing the deletion. (e.g. one time at the beginning of the application or with every deletion). If no application is open, the command has no effect. See Table 25. + +TABLE 25/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +### 5.2.23 VEMMI\_User\_Lock + +This service element shall be used to restrict any user input in the terminal until a VEMMI\_User\_Unlock is sent. See Table 26. + +TABLE 26/T.107 + +#### Parameters + +| Parameters | Description | +|------------|-------------| +| None | | + +### 5.2.24 VEMMI\_User\_Unlock + +This service element shall be used to permit user inputs in the terminal. See Table 27. + +TABLE 27/T.107 + +#### **Parameters** + +| Parameters | Description | +|------------|-------------| +| None | | + +### **5.2.25 VEMMI\_Resource\_Transfer** + +This service element shall be used to transfer files referenced by VEMMI resource objects from a VEMMI application to a VEMMI terminal. See Table 28. + +A file can be downloaded using one or more VEMMI\_Resource\_Transfer commands. A parameter of the VEMMI\_Resource\_Transfer command (TransferID) associates the command to a given resource transfer. This allows several resource transfers to be performed simultaneously with commands pertaining to different resource transfers interleaving each other without interference. + +The VEMMI\_Resource\_Transfer commands pertaining to the same resource transfer are numbered consecutively using the parameter BlockNumber. + +The first block of a given resource transfer shall always contain the following header information of the file: + +- filename; +- filesize; +- number of VEMMI\_Resource\_Transfer commands used to transmit the file; +- date of creation. + +The TransferType parameter of the VEMMI\_Resource\_Transfer command indicates if the VEMMI\_Resource\_Transfer command of a given resource transfer is: + +- the first command; +- an intermediate command; or +- if the resource transfer is aborted by the VEMMI application. + +TABLE 28/T.107 + +#### **Parameters** + +| Parameters | Description | +|-----------------|--------------------------------------------------------------------------| +| TransferType | First command, intermediate command, abort | +| TransferID | Transfer identifier | +| BlockNumber | Number of the command within a given resource transfer | +| FileInformation | Header information about the file | +| TotalBlocks | Number of VEMMI_Resource_Transfer commands used to transmit a given file | + +## 5.3 Service elements initiated by the terminal + +### 5.3.1 VEMMI\_Identify\_Term\_Cap\_Resp + +This service element shall be used to respond to a VEMMI\_Identify\_Term\_Cap request. See Table 29. + +The following information can be given: + +- VEMMI version identification; +- local storage support (supported/not supported); +- list of preferred user languages (string); +- system type (e.g. IBM compatible, Macintosh, ...), operating system (e.g. MS-DOS, OS2, Microsoft Windows, ...), operating system version (e.g. 3.1, ...) (string); +- a list of supported datatypes (reference to the VEMMI content encoding identification catalogue). + +TABLE 29/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------| +| SupportedVEMMIVersions | This parameter contains the VEMMI version identification | +| ContentList | The list gives references of the supported datatypes in the VEMMI content encoding identification catalogue | +| LocalStorage | Identifies the support of the local storage facility | +| PreferredUserLanguages | Languages preferred by the user (for multilingual applications)
The first language in the list is the most preferred. The list may contain only one language | +| SystemInfo | Information to support the correct use of operative objects (e.g. System Type, Operating System, Operating System Version) | + +### 5.3.2 VEMMI\_Object\_Retransmission + +This service element shall be used to request the VEMMI application to retransmit a VEMMI object. It shall be used only after: + +- the reception of a VEMMI\_Open\_Object command; +- a VEMMI\_Open\_Blocking\_Object command; +- a local action “Open object”; + +referring to an object that does not exist on the terminal. + +For the further processing of VEMMI commands until the requested object is received, the terminal shall apply one of the following rules. + +#### Rule A + +- inform the user about possible delay due to a retransmission (terminal dependent); +- send a VEMMI\_Object\_Retransmission request; +- execute all VEMMI commands and local actions which do not refer to the requested object; +- memorize all VEMMI commands and local actions which refer to the requested object. + +After the recreation and the opening of the requested object, the terminal shall: + +- resume the execution of the possibly suspended local action; +- resume the execution of the possibly memorized VEMMI commands received in the order of their reception. + +#### Rule B + +- lock the user; +- inform the user about possible delay due to a retransmission (terminal dependent); +- send a VEMMI\_Object\_Retransmission request; +- suspend and memorize any execution of VEMMI commands or local actions. + +After the recreation and the opening of the requested object, the terminal shall: + +- resume the execution of the possibly suspended local action; +- resume the execution of the possibly memorized VEMMI commands received in the order of their reception; +- unlock the user. + +See Table 30. + +TABLE 30/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | + +### 5.3.3 VEMMI\_User\_Data + +This service element shall be used to send user data corresponding to one object to the VEMMI application. See Table 31. + +TABLE 31/T.107 + +#### Parameters + +| Parameters | Description | +|------------------------------|-------------| +| Object Identification Number | | +| CompData | User inputs | + +### 5.3.4 VEMMI\_Open\_Application\_Resp + +This service element shall be used by the terminal to respond to a VEMMI\_Open\_Application command. See Table 32. + +TABLE 32/T.107 + +#### Parameters + +| Parameters | Description | +|----------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| OpenAppIResult | True: the application has been identified and the objects have been loaded
False: the application has not been identified, no objects have been loaded.
The parameters that were used with the VEMMI_Open_Application command are used to describe a new application environment | + +### 5.3.5 VEMMI\_Store\_Objects\_Resp + +This service element shall be used by the terminal to respond to a VEMMI\_Store\_Objects. See Table 33. + +TABLE 33/T.107 + +#### Parameters + +| Parameters | Description | +|-------------|-------------------------------------------------------------------------------| +| StoreResult | True: the objects have been stored
False: the objects have not been stored | + +### 5.3.6 VEMMI\_Error + +This service element shall be used only by the VEMMI terminal to report different error situations to the VEMMI application. + +A VEMMI\_Error command with the parameter Type of Error = “Out of memory” is only referring to the specified object. Other objects created after this one may be stored in the terminal. See Table 34. + +TABLE 34/T.107 + +#### Parameters + +| Parameters | Description | +|---------------------------------|-----------------------------------------------------| +| Object Identification Number | | +| ErrorType | | +| Component Identification Number | | +| ErrorComCode | Identification of the command that caused the error | + +The following types of errors are defined: + +- General error: +A general error has occurred. +- Unknown VEMMI command: +The VEMMI command code does not exist. +- Erroneous VEMMI command: +The VEMMI command received does not have the mandatory parameters or they have erroneous values. +- Object syntax error: +The description of a VEMMI element is not correct in an object creation or component modification. +- Unexpected VEMMI command: +The VEMMI command received is correct but it occurs at the wrong point in time. +- Out of memory: +The terminal does not have enough memory to store the data corresponding to an object creation or component modification. +- Service not supported: +The service requested is not supported. +- Object not supported. +- Data content type not supported. +- Invalid colour index. +- File not found. +- Conversion to bitmap failed. +- Object destroy indication (a closed object was destroyed by the terminal). +- Out of local permanent storage space. + +### 5.3.7 VEMMI\_Resource\_Transfer\_Abort + +This service element shall be used by the VEMMI terminal to abort a resource. See Table 35. + +TABLE 35/T.107 + +#### Parameters + +| Parameters | Description | +|------------|---------------------| +| TransferID | Transfer identifier | + +# 6 VEMMI objects introduction + +VEMMI objects offer a basic choice of dialogue elements needed by VEMMI applications. + +The following VEMMI objects are defined in this Recommendation: + +- application bar; +- button bar; +- pop-up menu; +- dialogue box; + +- message box. +- operative object; +- bitmap resource object; +- videotex resource object; +- text resource object; +- font resource object; +- metacode object. + +A VEMMI application can be designed using any of the defined objects. No particular VEMMI object or component is mandatory within a VEMMI application. All VEMMI objects may be multiple within a VEMMI application, except the Application Bar. Within an object, all components may be multiple except certain restrictions applying to specific components (see clause 7). + +## **6.1 The application bar** + +The Application Bar allows the user to make a choice between the different VEMMI application parts and sub-application parts offered by the selected VEMMI application. When used, the Application Bar is unique and located either on the top (horizontal Bar) or the left side (vertical Bar) of the DDA. + +### **6.1.1 Composition** + +The Application Bar is subdivided into three different logical groups of Menu Choice components. These groups differ in their behaviour and functionality. The three different groups are named: + +- bar; +- pull-down menu; +- cascading menu. + +The Bar is a horizontal or vertical list of Menu Choice components which represents the different parts of the VEMMI application. + +The Pull-Down Menus are vertical lists of Menu Choice components which are associated to the same Menu Choice component of the Bar. The Pull-Down Menus represent the different sub-application parts of the VEMMI application. + +The Cascading Menus are vertical lists of Menu Choice components which are associated to the same Menu Choice component of the Pull-Down Menu. The Cascading Menus represent the different sub-application parts of the VEMMI application. + +## **6.2 The button bar** + +The Button Bar permits a choice among a set of alternatives, at a given time, during the execution of the VEMMI application. Each choice is represented by a Button. The Button Bar may be located anywhere in the DDA. The Button Bar can be horizontal or vertical. + +### **6.2.1 Composition** + +The Button Bar is composed of a series of components, named Buttons. + +## **6.3 The pop-up menu** + +The Pop-Up Menu offers appropriate choices and sub-choices for a given VEMMI element in its current context. The Pop-Up Menu may be located anywhere in the DDA. + +### **6.3.1 Composition** + +The Pop-Up Menu is subdivided into two different logical groups of Menu Choice components. These groups differ in their behaviour and functionality. The two different groups are named: + +- primary pop-up menu; +- cascading menu. + +The Primary Pop-Up Menu is a vertical list of Menu Choice components which offers appropriate choices for a given VEMMI element in its current context. + +The Cascading Menu is a vertical list of Menu Choice components associated to the same Menu Choice component of the Primary Pop-Up Menu. The Cascading Menu offers appropriate sub-choices for a given VEMMI element in its current context. + +## **6.4 The dialogue box** + +The Dialogue Box is the object where the main interaction between the user and the VEMMI application takes place. To enable this interaction, a set of components is defined. These components can be classified as presentation or dialogue components. + +Presentation components are inaccessible; their purpose is only to present the different dialogue components coherently and attractively. + +Dialogue components permit the interaction between the user and the VEMMI application. + +Five presentation components are defined: + +- the Separator; +- the Frame; +- the Text Presentation Area; +- the Text component; +- the Graphic Output Area. + +Nine dialogue components are defined: + +- the Push Button; +- the Text Input Field; +- the Check Box; +- the Radio Button; +- the List Box; +- the Combination Box; +- the Slider; +- the Sensitive Area; +- the Sensitive Text. + +### **6.4.1 Composition** + +#### **6.4.1.1 The Separator component** + +A Separator is a horizontal or vertical solid line. Its goal is to visually separate different dialogue components within the Dialogue Box. + +#### **6.4.1.2 The Frame component** + +A Frame is a presentation element to visually separate a particular area of the Dialogue Box and its different components. + +#### **6.4.1.3 The Text Presentation Area component** + +The Text Presentation Area is a rectangular area in which text data is displayed. The goals of this component are: + +- to present text information; +- to title or to label dialogue components; +- to present results from the VEMMI application execution. + +#### **6.4.1.4 The Text component** + +The purpose of this component is to split large text data in units (text components) and to define the necessary structural information (concatenation of the text components) in order to be displayed in a text area. + +#### **6.4.1.5 The Graphic Output Area component** + +The purpose of this component is to present graphical data to the user. Several graphical data encoding formats are supported. + +#### **6.4.1.6 The Sensitive Text component** + +The purpose of this component is to define the activation and validation operations for sensitive text strings. + +#### **6.4.1.7 The Push Button component** + +The purpose of the Push Button is to trigger a local action to be immediately performed. + +#### **6.4.1.8 The Text Input Field component** + +The purpose of the Text Input Field is to collect text data, entered by the user. It is a rectangular area composed of a text label associated to an input area. + +#### **6.4.1.9 The Check Box component** + +The purpose of the Check Box is to enter and to display an independent user choice. A Check Box keeps the value marked or unmarked independently of any other Check Boxes. + +#### **6.4.1.10 The Radio Button component** + +The purpose of the Radio Button is to enter and to display a user choice. The Radio Button permits a single choice among several possibilities offered in a Radio Button group. The marking of one Radio Button leads to the unmarking of the other Radio Buttons belonging to the same Radio Button group. + +#### **6.4.1.11 The List Box component** + +The purpose of the List Box is to offer a single or multiple choice among a list of text items. The list is, generally, not entirely visible to the user, so different controls are offered to scroll the list up and down. + +#### **6.4.1.12 The Combination Box component** + +The purpose of the Combination Box is to combine the functionality of a single choice List Box with the functionality of a Text Input Field. It contains a list of text items the user can scroll through to complete the Text Input Field. A parameter of the Combination Box specifies whether the Text Input Field content can be edited or not. If the Text Input Field content can be edited, the user can type text directly into the Text Input Field. + +A variation of the Combination Box is a Drop Down Combination Box. It is composed of a Combination Box and a Push Button. Only the Text Input Field and the Push Button are displayed until the user selects the associated Push Button. The validation of the Push Button causes the display of the associated List Box. + +#### **6.4.1.13 The Slider component** + +The slider offers the selection of an analogue value by moving an adjustable marker on a slide bar between a minimum- and a maximum Value. The Intervals are set by the application. + +#### **6.4.1.14 The Sensitive Area component** + +The purpose of the Sensitive Area in the Dialog Box is to offer a selection area associated to an Output Area. + +## **6.5 Operative object** + +With this object an application references a program which will be linked to the VEMMI application. This object type provides a method to extend the capabilities of an application during runtime. + +## **6.6 Bitmap resource object** + +A bitmap object contains either the bitmap definition itself or only a reference to a file with the bitmap definition. + +## **6.7 Videotex resource object** + +A Videotex object contains either the Videotex content itself or only a reference to a file with the Videotex content. + +## **6.8 Text resource object** + +This object defines text content as a resource which can be referenced via the “Text Identification Number” (TIN). It contains either the text content itself or a reference to a file with the text content. + +## **6.9 Font resource object** + +This object combines a set of text attributes in a font resource which can be referenced via the FIN. + +## **6.10 Metacode object** + +The metacode object contains VEMMI commands. This object provides an easy way to avoid unnecessary dialogue steps with the host application. + +## **6.11 The message box** + +The purpose of the Message Box is to display information, not requested by a user but sent by the VEMMI application in response to an unexpected event, or when something undesirable might occur. + +# **7 Functional description** + +## **7.1 General rules for the behaviour of elements** + +### **7.1.1 User interaction** + +The user shall have the possibility to access and activate the different VEMMI elements. The terminal shall also enable the user to change the values of the VEMMI elements and to validate these inputs. + +### **7.1.2 Local actions and reports** + +The report of user inputs from the terminal to the server shall be induced by a report command defined in a local action by the VEMMI application. On executing a report command, the terminal shall send a VEMMI\_User\_Data command to the VEMMI application. The trigger events which induce the performance of local actions are: + +- activation of a component; +- validation of a component. + +The available report commands are: + +- report OIN + CIN; +- report the current values of the component; +- report the values of all components in this object; +- report all values of all components in the parent objects that have changed (also via a VEMMI\_Modify\_component) since the last report or since the object creation if this is the first report. + +Tables 36 and 37 show the possible trigger events and the possible reports for each component. + +The overall structure of local actions is defined in 4.8. + +TABLE 36/T.107 + +#### **Trigger events** + +| Component | Activation | Validation | +|------------------------|------------|------------| +| Menu choice bar | ✓ | ✓ | +| Menu choice pull-down | ✓ | ✓ | +| Menu choice cascading | ✓ | ✓ | +| Menu choice pop-up | ✓ | ✓ | +| Menu choice separator | | | +| Button | ✓ | ✓ | +| Separator | | | +| Frame | | | +| Text presentation area | | | +| Text component | | | +| Push button | ✓ | ✓ | +| Text input field | ✓ | ✓ | +| Check box | ✓ | ✓ | +| Radio button | ✓ | ✓ | +| List box | ✓ | ✓ | +| Combination box | ✓ | ✓ | +| Slider | ✓ | ✓ | +| Sensitive area | ✓ | ✓ | +| Sensitive text | | | +| Graphic output area | | | + +### 7.1.3 Relationship between objects and components + +The closed state of an object overrules the opened state of a component. If an object is closed, the entire object including all its components is removed from the screen, regardless if its components are in the opened state or not. The opened state of an object does not overrule the closed state of a component. If an object gets opened, the components which are in the closed state are not displayed. + +The inaccessible state parameter of an object overrules the accessible state parameter of a component. If an object is set inaccessible, the entire object including all its components becomes inaccessible, regardless if the components are accessible or not. The accessible state parameter of an object does not overrule the inaccessible state parameter of a component. If an object is set accessible, the user can only interact with those components that are accessible. + +TABLE 37/T.107 + +#### **Reports** + +| Component | CIN | Value of all Components | Value (Note) | +|------------------------------------------------------------------------------------------|-----|-------------------------|------------------| +| Menu choice bar | ✓ | | | +| Menu choice pull-down | ✓ | | | +| Menu choice cascading | ✓ | | | +| Menu choice pop-up | ✓ | | | +| Menu choice separator | | | | +| Button | ✓ | | | +| Menu choice | ✓ | | | +| Separator | | | | +| Frame | | | | +| Text presentation area | | | | +| Text component | | | | +| Push button | ✓ | ✓ | | +| Text input field | ✓ | ✓ | String | +| Check box | ✓ | ✓ | Boolean | +| Radio button | ✓ | ✓ | Boolean | +| List box | ✓ | ✓ | String list | +| Combination box | ✓ | ✓ | String | +| Slider | ✓ | ✓ | Integer, boolean | +| Sensitive area | ✓ | ✓ | | +| Sensitive text | | | | +| Graphic output area | | | | +| NOTE – The entries in this column specify the data type of the values that are reported. | | | | + +### **7.1.4 Open/close of audio, video, resource and metacode objects** + +If a sound object is opened, the sound shall be performed. At the end of the sound output, the object shall be considered closed. + +The same rule applies to video objects. If the object is opened, the video display process starts and at its end the object is closed. + +The open operation of a resource only checks if it is present at the terminal. + +A metacode object is processed by the open operation. At the end of processing, it is considered closed. + +### **7.1.5 Maximize operation** + +NOTE – The operation described in the following subclause is not mandatory for a VEMMI terminal. If a terminal does not implement this operation, it shall ignore the corresponding attributes and operations. + +An object can be defined as maximizable. In this case it is displayed with a maximize button in its title row and upon the validation of this button it is displayed enlarged. The enlarged object is completed with a restore button and upon a validation of the restore button, the object is re-displayed in its initial size. These operations are terminal and UI dependent, especially the enlarged size. The host application only can mark an object as maximizable. + +All object elements and components, except the Text Presentation Area, are enlarged on a terminal specific basis. The Text Presentation Area component of a Dialogue Box has a specific behaviour, in order to allow an enlarged object to add locally more text content in its display area. If the Text Presentation Area contains in its initial size the whole text, the maximize operation is terminal dependent. If the text is only partly displayed in its initial position, the terminal shall add additional text in the maximized object. The enlarged object can display the text in a new formatted form. This can be set by the host. + +If the object is closed in its enlarged size and later reopened it is displayed in its initial (not enlarged) size. If a maximized object is deactivated it keeps its size. + +Additional local operations on objects, which are not definable by the host can be offered to the user on a terminal specific basis. These can be: minimize, moving, iconize, unidirectional increase and decrease, etc. + +### 7.1.6 Notational Conventions + +For the next subclauses the following notational conventions apply: + +- 1) In the following subclauses of this clause each object and component description contains an attribute list. These lists contain those attributes that are needed to describe the properties of the elements. The precise syntax of the element encoding is defined in clause 9. +- 2) The identification numbers for resource objects, BIN (Bitmap Identification Number), FIN (Font Identification Number), TIN (Text Identification Number), VIN (Videotex Identification Number) are special cases of OINs and used on the same level, e.g. as parameters of VEMMI commands. Different from them the CIN always denotes a component. + +The naming conventions for the boolean attributes in the VEMMI element description follows the following rule: + +- If the attribute is present in the encoding, its boolean value corresponds to the value expressed by its name. + +#### Example + +The default value of the state “Opened” is true. If the “closed” attribute is present in the encoding of a VEMMI element, the element shall be in the “Closed” state. If the “closed” attribute is not present in the encoding of a VEMMI element, the element shall be in its default state, the “Opened” state. + +### 7.1.7 Mnemonic + +When text data is used in a component, the text can contain the character “&” which marks the next character as a mnemonic key. The mnemonic key can be used to validate or activate the component. To present the “&” character in a text it shall be doubled (e.g.: text content = “&Cats && Dogs”; text presented to the user “&Cats & Dogs”). + +## 7.2 Text formats + +### 7.2.1 VEMMI high quality text + +The implementation of text attributes (change of text font, text size, etc. inside a text string) and the definition of sensitive areas for text (sensitive text or “hot-spot”) is realized with “In-text attributes”. These are applicable for the following elements: + +- Text Presentation Area components of a Dialogue box. +- Labels. +- 1) *Text attributes* + +The attributed font can be changed inside a text output operation. The font is referenced via the FIN. A selected new font applies to all subsequent text up to the next in-text attribute which changes the font or to the end of the component. The initial attributed font applied to the first text of the component is defined as an additional attribute in the component. + +The following example shows the use of in-text attributes. The brackets <...> denote attributes of the components with their parameter. + +#### **Example:** + +..... + + = “Customer service note:(CR,LF,CR,LF)” + + + + = “110 size negatives” + + + + = “must not be cut but must be returned in strip form for reprinting.” + + + + = “If they are cut we are unable to make prints from them.” + + + + = “(CR,LF,CR,LF)Issued by the A.P.L.” + +..... + +FIN 5 is defined as ROMAN, height 12. + +FIN 6 is defined as ROMAN, height 12, bold, underlined. + +FIN 7 is defined as SWISS, height 8. + +The above text sequence with in-text attributes might look as follows: + +Customer service note: + +110 size negatives ***must not be cut but must be returned in strip form for reprinting.*** If they are cut we are unable to make prints from them. + +Issued by the A.P.L. + +#### 2) *In-text attributes for the definition of sensitive text* + +Each text string defined as sensitive has the reference to a Sensitive Text component. This component contains two attributes which define the activation and validation operations to be performed upon the user interaction with the Sensitive Text. + +The two groups of attributes can be mixed in one text component, so that the application can apply text attributes, e.g. colour, to sensitive strings. Such a string may appear green and possibly in addition highlighted, in order to be easily distinguished from the plain text, which might be black on white. With these attributes, the application can offer to the user “hypertext”-like output with VEMMI. + +### 7.2.2 Text labels and titles + +The text contents of labels and titles are clipped at the borders of their containers. This shall be applied to the following attributes: + +- all title attributes; +- all label attributes; +- text content attribute of Menu Choice components; +- list text attribute of List Box and Combination Box components. + +## 7.3 The Application Bar + +The Application Bar is subdivided into three different logical groups of Menu Choice components. These groups differ in their behaviour and functionality. The three different groups are named: + +- Bar; +- Pull-Down Menu; +- Cascading Menu. + +NOTE 1 – The vertical representation of the Application Bar is an optional feature for a VEMMI terminal. If the vertical attribute is present and set true in the encoding of an Application Bar, the terminal may ignore it and present the Application Bar horizontally. However, no error message shall be sent to the host. + +NOTE 2 – All positioning and dimensioning attributes for an Application Bar and for all of its Menu Choice components are optional. If positioning or dimensioning attributes are defined in the encoding of an Application Bar, the terminal may ignore them and present the Application Bar starting on the top left corner of the DDA and dimension it according to the space requirements of the text content. However, no error message shall be sent to the host. + +The Bar is a horizontal or vertical list of Menu Choice components. The Pull-Down Menus are vertical lists of Menu Choice components which are associated to the same Menu Choice component of the Bar. The Cascading Menus are vertical lists of Menu Choice, components which are associated to the same Menu Choice component of the Pull-Down Menu. + +All Menu Choice components of the Application Bar shall only have text content. + +A Menu Choice Separator component can be used to visually separate menu choice components in a logical group. It is defined by setting the attribute “Separator” with the definition of a regular Menu Choice. + +The structure of the Application Bar Object is given, by the canonical descending order of its components (path left to right with priority to the depth). + +In the following Application Bar example, the canonical descending order of the components is: + +(AB(FG(IJK)H)CDE(L)) + +| | | | | | +|---|---|---|---|---| +| A | B | C | D | E | +| | F | | | L | +| | G | I | | | +| | H | J | | | +| | | K | | | + +NOTE 3– The use of parenthesis in the above example is only to show the different levels of encapsulation of the different object groups for the path of description. + +The description of the structure of the object is then: + +- Object: Application Bar. +- Component: Menu Choice Bar A. +- Component: Menu Choice Bar B. +- Component: Menu Choice Pull-Down F. +- Component: Menu Choice Pull-Down G. +- Component: Menu Choice Cascading I. +- Component: Menu Choice Cascading J. +- Component: Menu Choice Cascading K. +- Component: Menu Choice Pull-Down H. +- Component: Menu Choice Bar C. +- Component: Menu Choice Bar D. +- Component: Menu Choice Bar E. +- Component: Menu Choice Pull-Down L. + +### **General Visual Aspect** (see Figures 7 and 8) + +![Diagram of a horizontal application bar layout showing choices and their sub-choices.](fc02903382cebe6fc11e4c0d74b5313f_img.jpg) + +The diagram illustrates a horizontal application bar layout. A large rectangle represents the bar. At the top left, a bracket labeled 'XPos' indicates the horizontal position, and a bracket labeled 'Height' indicates the vertical height. The bar is divided into sections. The first section is labeled 'Choice 1'. The second section is labeled 'Choice 2'. The third section is labeled 'Choice 3' and is highlighted with a grey background. This 'Choice 3' section is further divided into a vertical list of sub-choices: 'Choice 3.1', 'Choice 3.2', 'Choice 3.3', 'Choice 3.4', 'Choice 3.5', 'Choice 3.6', 'Choice 3.7', 'Choice 3.8', and 'Choice 3.9'. To the right of the 'Choice 3' section, there are two more sections labeled 'Choice 3'. The first of these sections is further divided into a vertical list of sub-choices: 'Choice 3.7.1', 'Choice 3.7.2', 'Choice 3.7.3', 'Choice 3.7.4', and 'Choice 3.7.5'. + +Diagram of a horizontal application bar layout showing choices and their sub-choices. + +T0823880-95/d07 + +FIGURE 7/T.107 + +![Diagram of a vertical application bar layout showing choices and their sub-choices.](bccc028d0e75bc30c41528056f581545_img.jpg) + +The diagram illustrates a vertical application bar layout. A large rectangle represents the bar. At the top left, a bracket labeled 'Width' indicates the horizontal width, and a bracket labeled 'YPos' indicates the vertical position. The bar is divided into sections. The first section is labeled '1'. The second section is labeled '2'. The third section is labeled '3'. The fourth section is labeled '4' and is further divided into a vertical list of sub-choices: 'Choice 8.1', 'Choice 8.2', 'Choice 8.3', 'Choice 8.4', 'Choice 8.5', 'Choice 8.6', and 'Choice 8.7'. To the right of the 'Choice 8.3' section, there are two more sections labeled 'Choice 8.7.1', 'Choice 8.7.2', 'Choice 8.7.3', and 'Choice 8.7.4'. + +Diagram of a vertical application bar layout showing choices and their sub-choices. + +T0823890-95/d08 + +FIGURE 8/T.107 + +### **Attributes** + +- Vertical: The Application Bar shall be presented vertical (see Note 1). +- XPos: This attribute carries the horizontal position of the element in NDC. It is only applicable to horizontal Application Bars (see Note 2). +- YPos: This attribute carries the vertical position of the element in NDC. It is only applicable to vertical Application Bars (see Note 2). +- Height: This attribute carries the height of the Bar. It is only applicable to horizontal Application Bars (see Note 2). +- Width: This attribute carries the width of the Bar. It is only applicable to vertical Application Bars (see Note 2). + +- **FirstActive:** This attribute carries the CIN of the Menu Choice which is active by default, the first time the object is opened. +- **Closed:** The element shall be in the closed state. +- **NotAccessible:** The object is not accessible. + +### 7.3.1 Composition + +#### 7.3.1.1 Menu Choice components of the Bar + +##### Description + +The Bar is a consecutive list of Menu Choices positioned side by side horizontally, or vertically. + +Horizontal representation: + +- the Application Bar shall be presented at the top of the DDA; +- the number of rows allocated for each Menu Choice shall be the same. + +Vertical representation: + +- the Application Bar shall be presented at the leftmost part of the DDA; +- the number of columns allocated for each Menu Choice shall be the same. + +##### Behaviour + +When the Application Bar is active, the terminal shall emphasize one Menu Choice, and offer shifting and validation facilities to the user. A mnemonic key can be used to validate the Menu Choice (see 7.1.7). + +If a Menu Choice of the Bar is validated the associated local action shall be performed and then the associated Pull-Down Menu shall be opened (the Menu Choice remains emphasized). + +##### Interactive functionality + +- shifting; +- validation. + +**Visual aspect** (see Figures 9 and 10) + +![Diagram of a horizontal menu bar showing four choices: Choice 1, Choice 2, Choice 3, and Choice 4. Each choice is contained within a rectangular box of equal width, separated by vertical dashed lines. Above each box is the label 'Width'. The entire menu bar is enclosed in a larger rectangular frame.](2c3bf03decbeb6a8038deccc5a796b46_img.jpg) + +| Width | Width | Width | Width | +|----------|----------|----------|----------| +| Choice 1 | Choice 2 | Choice 3 | Choice 4 | + +Diagram of a horizontal menu bar showing four choices: Choice 1, Choice 2, Choice 3, and Choice 4. Each choice is contained within a rectangular box of equal width, separated by vertical dashed lines. Above each box is the label 'Width'. The entire menu bar is enclosed in a larger rectangular frame. + +T0815510-94/d09 + +FIGURE 9/T.107 +Horizontal menu bar + +![Diagram of a vertical menu bar showing 9 choices. Choice 4 is split into two rows. Each choice has a 'Height' attribute. Choice 9 has a 'Mnemonic' attribute.](89f8aefc01866631793087542316cef2_img.jpg) + +| | | +|---------------------|--------| +| Choice 1 | Height | +| Choice 2 | Height | +| Choice 3 | Height | +| Choice 4
Two row | Height | +| Choice 5 | Height | +| Choice 6 | Height | +| Choice 7 | Height | +| Choice 8 | Height | +| Choice 9 | Height | + +Mnemonic + +Diagram of a vertical menu bar showing 9 choices. Choice 4 is split into two rows. Each choice has a 'Height' attribute. Choice 9 has a 'Mnemonic' attribute. + +T0815520-94/d10 + +FIGURE 10/T.107 +Vertical menu bar + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- Height: This attribute carries the height of the component. It is only applicable to vertical Bars (see , 7.3, Note 2). +- Width: This attribute carries the width of the component. It is only applicable to horizontal Bars (see 7.3, Note 2). +- NotAccessible: The element shall not be accessible. +- Text: This attribute carries the text content of the component. +- LocActAct: This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- LocActVal: This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +#### 7.3.1.2 Menu Choice components of the Pull-Down Menu + +##### Description + +The Pull-Down Menu is a consecutive list of Menu Choices components associated to the same Menu Choice of the Bar and presented vertically on several rows. + +The number of columns allocated for each Menu Choice shall be the same. + +The Pull-Down Menu shall be positioned next to the associated Menu Choice of the Bar. + +A Separator can be used in an Pull-Down Menu to visually separate different Menu Choices. + +##### Behaviour + +When the Pull-Down Menu is active, the terminal shall emphasize one Menu Choice, and offer to the user shifting and validation facilities. A mnemonic key can be used to validate the Menu Choice (see 7.1.7). + +If a Menu Choice is validated the associated local action shall be performed and then the associated Cascading Menu shall be opened (the Menu Choice remains emphasized). If no Cascading Menu is associated to the Menu Choice after a user validation, the associated local action shall be performed and then the Pull-Down Menu shall be closed. + +##### Interactive functionality + +- shifting; +- validation. + +**Visual aspect** (see Figures 11 and 12) + +![Diagram of a pull-down menu showing a grid of choices. Choice 2 is highlighted, and its sub-choices are shown in a separate column. Dimensions Width and Height are indicated.](2cf3896394a2342a2b46c504ab9a8830_img.jpg) + +The diagram illustrates a pull-down menu structure. It features a horizontal row of five choices: Choice 1, Choice 2, Choice 3, Choice 4, and Choice 5. Choice 2 is highlighted. Below Choice 2, a vertical list of sub-choices is shown: Choice 2.1, Choice 2.2, Two row Choice 2.3, Choice 2.4, and Choice 2.5. Choice 2.4 is highlighted. To the right of the sub-choices, the word 'Height' is repeated for each row. A horizontal dimension line labeled 'Width' spans the width of the sub-choice column. A vertical dimension line labeled 'Height' spans the height of the sub-choice column. The entire structure is enclosed in a rectangular frame. + +T0824320-95/d11 + +Diagram of a pull-down menu showing a grid of choices. Choice 2 is highlighted, and its sub-choices are shown in a separate column. Dimensions Width and Height are indicated. + +FIGURE 11/T.107 + +###### Pull-down menu + +![Diagram of a pull-down menu showing a grid of choices. Choice 2 is highlighted, and its sub-choices are shown in a separate column. Dimensions Width and Height are indicated.](408c4798ea60469e0728a7cbbd598668_img.jpg) + +The diagram illustrates a pull-down menu structure. It features a vertical list of nine choices: Choice 1, Choice 2, Choice 3, Choice 4, Two row Choice 5, Choice 6, Choice 7, Choice 8, and Choice 9. Choice 2 is highlighted. To the right of the main list, a vertical list of sub-choices is shown: Choice 2.1, Choice 2.2, Choice 2.3, Choice 2.4, and Two row Choice 2.5. Choice 2.4 is highlighted. To the right of the sub-choices, the word 'Height' is repeated for each row. A horizontal dimension line labeled 'Width' spans the width of the sub-choice column. A vertical dimension line labeled 'Height' spans the height of the sub-choice column. The entire structure is enclosed in a rectangular frame. + +T0824330-95/d12 + +Diagram of a pull-down menu showing a grid of choices. Choice 2 is highlighted, and its sub-choices are shown in a separate column. Dimensions Width and Height are indicated. + +FIGURE 12/T.107 + +###### Pull-down menu + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- Height: This attribute carries the height of the component (see 7.3, Note 2). +- Width: This attribute carries the width of the component. It shall be equal to all Menu Choices of the Pull Down Menu (see 7.3, Note 2). +- NotAccessible: The element shall not be accessible. +- Text: This attribute carries the text content of the component. +- Separated: A Separator shall be drawn between the elements. +- LocActAct: This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- LocActVal: This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +#### 7.3.1.3 Menu Choice components of the Cascading Menu + +Menu Choice components of Cascading Menu are common to the Pull-Down Menu and the Pop-Up Menu. + +##### Description + +The Cascading Menu is a consecutive list of Menu Choices associated to the same Menu Choice of the Pull-Down Menu or Pop-Up Menu and presented vertically on several rows. + +The number of columns allocated for each Menu Choice shall be the same. + +The Cascading Menu shall be positioned next to the associated Pull-Down Menu or Pop-Up Menu. + +A Separator can be used in a Cascading Menu to visually separate different Menu Choices. + +Figure 13 shows the recommended presentation for a Cascading Menu. If the terminal is not able to present a Cascading Menu like shown in Figure 13 it can, as a fallback solution, present the Menu Choices of the Cascading Menu in the Pull-Down Menu but it should visually associate the Menu Choices of the Cascading Menu to the corresponding Menu Choice of the Pull-Down Menu. The terminal should set the Menu Choice in the Pull-Down Menu, to which the Cascading Menu is associated, inaccessible and present it as a title for the Menu Choices of the Cascading Menu (see Figure 14). + +##### Behaviour + +When the Cascading Menu is active, the terminal shall emphasize one Menu Choice, and offer to the user shifting and validation facilities. A mnemonic key can be used to validate the Menu Choice (see subclause 7.1.7). + +After the validation of a Menu Choice, the associated local action shall be performed and then the Cascading Menu and the Pull-Down Menu (Pop-Up Menu) shall be closed. + +##### Interactive functionality + +- shifting; +- validation. + +**Visual aspect** (see Figure 13 and 14) + +![Diagram of a cascading menu (recommended presentation)](7d929ba1b7d09ea8e00b9e7abbbe50c9_img.jpg) + +The diagram illustrates a cascading menu structure. At the top, a horizontal bar contains five choices: Choice 1, Choice 2, Choice 3, Choice 4, and Choice 5. Below Choice 2, a vertical list of choices is shown: Choice 2.1, Choice 2.2, Choice 2.3, and Choice 2.4. Choice 2.3 is highlighted with a grey background. Below Choice 2.3, a sub-menu is displayed, containing two rows: 'Two row Choice 2.3.1' and 'Choice 2.3.2'. The sub-menu is also highlighted with a grey background. To the right of the sub-menu, two vertical dimension lines are labeled 'Height'. Below the sub-menu, a horizontal dimension line is labeled 'Width'. The entire diagram is enclosed in a large rectangular frame. + +T0823920-95/d13 + +Diagram of a cascading menu (recommended presentation) + +FIGURE 13/T.107 +**Cascading menu (recommended presentation)** + +![Diagram of a cascading menu (fallback presentation)](3337af75dfee8af7687b4f49914d6c93_img.jpg) + +The diagram illustrates a cascading menu structure in a fallback presentation. At the top, a horizontal bar contains five choices: Choice 1, Choice 2, Choice 3, Choice 4, and Choice 5. Below Choice 2, a vertical list of choices is shown: Choice 2.1, Choice 2.2, Choice 2.3, and Choice 2.4. Choice 2.3 is highlighted with a grey background. Below Choice 2.3, a sub-menu is displayed, containing two rows: 'Two row Choice 2.3.1' and 'Choice 2.3.2'. The sub-menu is also highlighted with a grey background. The entire diagram is enclosed in a large rectangular frame. + +T0823930-95/d14 + +Diagram of a cascading menu (fallback presentation) + +FIGURE 14/T.107 +**Cascading menu (fallback presentation)** + +#### **Attributes** + +- CIN: This attribute carries the Component Identification Number. +- Height: This attribute carries the height of the component (see 7.3, Note 2 ). +- Width: This attribute carries the width of the component. It shall be equal to all Menu Choices of the Cascading Menu (see 7.3, Note 2 ). +- NotAccessible: The element shall not be accessible. + +- Text: This attribute carries the text content of the component. +- Separated: A Separator shall be drawn between the elements. +- LocActAct: This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- LocActVal: This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +## 7.4 The Button Bar + +### Description + +The Button Bar is a consecutive list of Buttons positioned side by side horizontally, or vertically. + +Horizontal representation: + +- the number of rows allocated for each Button shall be the same. + +Vertical representation: + +- the number of columns allocated for each Button shall be the same. + +NOTE – If the “Height” and the “Width” attribute are present in the definition of a Bar all Buttons in the Bar shall have the same dimensions. The dimensioning attributes for the components of the Button Bar shall then not be present. If only the “Height” attribute is present in the definition of a horizontal Button Bar, it denotes the height for the entire object. The width for the components is then given with each component. If only the “Width” attribute is present in the definition of a vertical Button Bar it denotes the width for the entire object. The height for the components is then given with each component. + +### Behaviour + +When the Button Bar is active, the terminal shall emphasize one Button, and offer to the user shifting and validation facilities. + +#### Interactive functionality + +- shifting; +- validation. + +**Visual aspect** (see Figure 15) + +![Diagram illustrating the visual aspect of a Button Bar. It shows two configurations: a Horizontal Bar and a Vertical Bar. The Horizontal Bar is a row of six buttons with icons: a hand, a piggy bank, a document, a list, a hand, and a question mark. The Vertical Bar is a column of six buttons with the same icons. Dimensioning lines indicate XPos and YPos for the bars and their components. The Horizontal Bar is labeled 'Horizontal Bar' and 'Height'. The Vertical Bar is labeled 'Vertical Bar' and 'Width'. The diagram is signed 'DDA' in the bottom right corner.](167a6aea873669eb91492f33d35d16de_img.jpg) + +The diagram illustrates the visual aspect of a Button Bar. It shows two configurations: a Horizontal Bar and a Vertical Bar. The Horizontal Bar is a row of six buttons with icons: a hand, a piggy bank, a document, a list, a hand, and a question mark. The Vertical Bar is a column of six buttons with the same icons. Dimensioning lines indicate XPos and YPos for the bars and their components. The Horizontal Bar is labeled 'Horizontal Bar' and 'Height'. The Vertical Bar is labeled 'Vertical Bar' and 'Width'. The diagram is signed 'DDA' in the bottom right corner. + +Diagram illustrating the visual aspect of a Button Bar. It shows two configurations: a Horizontal Bar and a Vertical Bar. The Horizontal Bar is a row of six buttons with icons: a hand, a piggy bank, a document, a list, a hand, and a question mark. The Vertical Bar is a column of six buttons with the same icons. Dimensioning lines indicate XPos and YPos for the bars and their components. The Horizontal Bar is labeled 'Horizontal Bar' and 'Height'. The Vertical Bar is labeled 'Vertical Bar' and 'Width'. The diagram is signed 'DDA' in the bottom right corner. + +FIGURE 15/T.107 +Button bar + +### Attributes + +- XPos: This attribute carries the horizontal position of the element in Normalized Device Coordinate (NDC). +- YPos: This attribute carries the vertical position of the element in NDC. +- Vertical: Boolean switch between the alternatives. +- Height: This attribute carries the height of the Button Bar. It is only applicable to horizontal Button Bars (see Note). +- Width: This attribute carries the width of the Button Bar. It is only applicable to vertical Button Bars (see Note). +- FirstActive: This attribute carries the CIN of the Button which is active by default, the first time the object is opened. +- Modal: The element shall be modal. +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. + +### 7.4.1 Composition + +#### 7.4.1.1 The Button component + +##### Description + +The Button is a rectangular area in the DDA. + +If formed with text data it should be represented by a text label, possibly associated with a graphic to draw the shape of the button. The button graphic shape shall be included in the space allocated by the VEMMI application for the whole Button component. If the graphic shape does not cover the entire space allocated for the button, the terminal can resize the content. The terminal may centre the text data in the element display area reserved by the VEMMI application for the component. + +The drawing of the Button and the possible visual trigger effect are terminal dependent. + +##### Behaviour + +When a Button is active, the terminal shall emphasize it. A mnemonic key can be used to validate the Button (see 7.1.7). + +When a trigger effect is implemented, the Button shall go back to the initial display state after user validation. + +##### Interactive functionality + +- activation; +- validation. + +**Visual aspect** (see Figure 16) + +![Diagram of a button component showing its visual aspects.](910aca984b27c368361b38751ab5eea6_img.jpg) + +The diagram illustrates a rectangular button component. Inside the rectangle, the text 'OK' is centered. Above the rectangle, a horizontal dimension line is labeled 'Width'. To the right of the rectangle, a vertical dimension line is labeled 'Height'. Below the rectangle, a label 'Mnemonic' is connected to the 'OK' text by a diagonal line. Further down, the text 'T0815570-94/d16' is displayed. + +Diagram of a button component showing its visual aspects. + +FIGURE 16/T.107 + +##### Button + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- Height: This attribute carries the height of the component. It is only applicable to Buttons of vertical Button Bars (see 7.4, Note). +- Width: This attribute carries the width of the component. It is only applicable to Buttons of horizontal Button Bars (see 7.4, Note). +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. +- BIN: The BIN of the component. +- Text: The text content of the component. +- LocActAct: This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- LocActVal: This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +## 7.5 The Pop-Up Menu + +The Pop-Up Menu is subdivided into two different logical groups of Menu Choice components. These groups differ in their behaviour and functionality. The two different groups are named: + +- Primary Pop-Up Menu; +- Cascading Menu. + +The Primary Pop-Up Menu is a vertical list of Menu Choice components. The Cascading Menu is a vertical list of Menu Choice components associated to the same Menu Choice component of the Primary Pop-Up Menu. + +A Menu Choice Separator can be used to visually separate menu choice components in a logical group. It is defined by setting the attribute “Separator” with the definition of a regular Menu Choice. + +The structure of the Pop-Up Menu Object is given, with the following conventions, by the canonical descending order of its components (path top down). + +In the following Pop-Up Menu example, the canonical descending order of the components is: + +(BFG(IJK)H) + +| | | +|---|---| +| B | | +| F | | +| G | I | +| H | J | +| | K | + +NOTE 1 – The parenthesis in the above example are only for showing the different levels of encapsulation of the different object groups for the path of description. + +The description of the structure of the object is then: + +- Object: Pop-Up Menu. +- Component: Menu Choice Pop-Up B. +- Component: Menu Choice Pop-Up F. +- Component: Menu Choice Pop-Up G. +- Component: Menu Choice Cascading I. + +- Component: Menu Choice Cascading J. +- Component: Menu Choice Cascading K. +- Component: Menu Choice Pop-Up H. + +### Interactive functionalities + +- shifting; +- validation. + +**General visual aspect** (see Figure 17) + +![Diagram of a Pop-Up Menu structure showing dimensions and content.](212c50c4e3d043c989037a01e13c1a98_img.jpg) + +The diagram illustrates a Pop-Up Menu structure. A large rectangle represents the menu area. Its horizontal position is labeled 'XPos' and its vertical position is labeled 'YPos'. Inside this area, a smaller rectangle represents the menu content. Its width is labeled 'Width'. The menu content is divided into rows. The first row contains the number '1'. The second row contains the number '2'. The third row contains the number '3'. The fourth row contains the number '4'. The fifth row contains the number '5' and the text 'Choice 5.1'. The sixth row contains the number '6' and the text 'Choice 5.2'. The seventh row contains the number '7' and the text 'Choice 5.3'. The text 'DDA' is located in the bottom right corner of the menu area. The text 'T0823940-95/d17' is located in the bottom right corner of the diagram. + +Diagram of a Pop-Up Menu structure showing dimensions and content. + +FIGURE 17/T.107 + +A text title may be given to the Pop-Up Menu which shall be displayed in its first row of the Primary Pop-Up Menu. + +NOTE 2 – All dimensioning attributes for the Menu Choice components of the Pop-Up Menu are optional. If dimensioning attributes are defined in the encoding of a Pop-Up Menu, the terminal may ignore them and dimension it according to the space requirements of the text content. However, no error message shall be sent to the host. + +### Attributes + +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Width: This attribute carries the width of the Pop-Up Menu (see Note 2). +- Title: This attribute carries the title of the object. The title shall be displayed in the first row of the object. +- TitleFont: This attribute carries the FIN of the title. +- FirstActive: This attribute carries the CIN of the component which is active by default, the first time the object is opened. +- Modal: The element shall be modal. +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. + +### 7.5.1 Composition + +#### 7.5.1.1 Menu choice components of the primary pop-up menu + +##### Description + +The Primary Pop-Up Menu is a consecutive list of Menu Choices and presented vertically on several rows. + +The number of columns allocated for each Menu Choice shall be the same. + +A Separator can be used in a Primary Pop-Up Menu to visually separate different Menu Choices. + +##### Behaviour + +When the Primary Pop-Up Menu is active, the terminal shall emphasize one Menu Choice, and offer to the user shifting and validation facilities. A mnemonic key can be used to validate the Menu Choice (see 7.1.7). + +If a Pop-Up Menu component is validated the associated local action shall be performed and then the associated Cascading Menu shall be opened (the Pop-Up Menu component remains emphasized). If no Cascading Menu is associated to the Menu Choice after a user validation, the associated local action shall be performed and then the Pop-Up Menu shall be closed. + +##### Interactive functionality + +- shifting; +- validation. + +**Visual aspect** (see Figure 18) + +![Diagram of a pop-up menu structure showing five choices with their respective heights.](a1dc2b799cd6ca93414adab971763c3e_img.jpg) + +The diagram illustrates a pop-up menu structure. It consists of a large rectangular container. Inside, there is a table-like structure with five rows. Each row contains a menu choice and its corresponding height. The choices are: 'Choice 1', 'Choice 2', 'Two row Choice 3', 'Choice 4', and 'Choice 5'. The heights are all labeled as 'Height'. The 'Two row Choice 3' is visually represented by two rows within its cell. The 'Choice 4' row is shaded gray. Dashed lines separate the rows. The text 'T0823950-95/d18' is located at the bottom right of the container. + +| | | +|---------------------|--------| +| Choice 1 | Height | +| Choice 2 | Height | +| Two row
Choice 3 | Height | +| Choice 4 | Height | +| Choice 5 | Height | + +T0823950-95/d18 + +Diagram of a pop-up menu structure showing five choices with their respective heights. + +FIGURE 18/T.107 + +##### Pop-up menu + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- Height: This attribute carries the height of the component (see 7.5, Note 2). +- Closed: The element shall be in the closed state. + +- **NotAccessible:** The element shall not be accessible. +- **Text:** This attribute carries the text content of the component. +- **Separated:** The elements shall be separated. +- **LocActAct:** This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- **LocActVal:** This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +#### 7.5.1.2 Menu choice components of the cascading menu + +##### Description, behaviour, interactive functionality, attributes + +See 7.3.1.3. + +**Visual aspect** (see Figure 19) + +![Diagram illustrating the recommended presentation of a pop-up menu with associated cascading menu. The diagram shows a vertical list of choices (Choice 1 to Choice 7) on the left, and a cascading menu structure on the right. The cascading menu has three columns: the first column contains 'Choice 3', 'Choice 4', 'Choice 5', 'Choice 6', and 'Choice 7'; the second column contains 'Choice 3.1', 'Choice 3.2', 'Choice 3.3', 'Choice 3.4', and 'Three row Choice 3.5'; the third column contains 'Height' repeated five times. A horizontal line separates the first column from the second, and a vertical line separates the second from the third. A bracket labeled 'Width' is shown below the second column, and a bracket labeled 'Height' is shown to the right of the third column.](977811d1c73b74f801be9f4c376694ca_img.jpg) + +Diagram illustrating the recommended presentation of a pop-up menu with associated cascading menu. The diagram shows a vertical list of choices (Choice 1 to Choice 7) on the left, and a cascading menu structure on the right. The cascading menu has three columns: the first column contains 'Choice 3', 'Choice 4', 'Choice 5', 'Choice 6', and 'Choice 7'; the second column contains 'Choice 3.1', 'Choice 3.2', 'Choice 3.3', 'Choice 3.4', and 'Three row Choice 3.5'; the third column contains 'Height' repeated five times. A horizontal line separates the first column from the second, and a vertical line separates the second from the third. A bracket labeled 'Width' is shown below the second column, and a bracket labeled 'Height' is shown to the right of the third column. + +T0823960-95/d19 + +FIGURE 19/T.107 + +**Recommended presentation of a pop-up menu +with associated cascading menu** + +## 7.6 The Dialogue Box + +### Description + +The Dialogue Box is a rectangular area in the DDA which contains VEMMI components in order to establish user interaction. + +The components themselves contain (or have references to) other components or resource objects. Figure 20 shows the relationship. Each arrow indicates a possible reference to a component or a resource object. These references can be multiple as well as the dialogue box can contain several components of the same type. + +![Figure 20/T.107: Element relationships within the dialogue box. This diagram shows a 'Dialogue box' at the top with arrows pointing to a vertical list of components: Separator, Frame, Graphic output area, Text area, Text input field, Push button, Check box, Radio button, List box, Combo box, Slider, and Sensitive area. The 'Graphic output area' has arrows pointing to 'VIN' and 'BIN'. The 'Text area' has an arrow pointing to 'FIN'. The 'Text input field' has an arrow pointing to 'FIN'. The 'Push button' has an arrow pointing to 'BIN'. The 'Check box' has an arrow pointing to 'FIN'. The 'Radio button' has an arrow pointing to 'FIN'. The 'List box' has an arrow pointing to 'BIN'. The 'Combo box' has an arrow pointing to 'BIN'. The 'Slider' has an arrow pointing to 'FIN'. The 'Sensitive area' has no outgoing arrows. The 'Text area' also has an arrow pointing to a 'Text component' box. The 'Text component' box has arrows pointing to 'FIN', 'TIN', and 'Sensitive text'. The 'Sensitive text' box has an arrow pointing to 'FIN'. The 'Dialogue box' also has an arrow pointing to 'BIN'.](2cc973099f02f2cc67558feea3b18cde_img.jpg) + +``` + +graph TD + DB[Dialogue box] --> S[Separator] + DB --> F[Frame] + DB --> GOA[Graphic output area] + DB --> TA[Text area] + DB --> TIF[Text input field] + DB --> PB[Push button] + DB --> CB[Check box] + DB --> RB[Radio button] + DB --> LB[List box] + DB --> CBOX[Combo box] + DB --> SL[Slider] + DB --> SA[Sensitive area] + DB --> BIN1((BIN)) + + GOA --> VIN((VIN)) + GOA --> BIN2((BIN)) + + TA --> FIN1((FIN)) + TA --> TC[Text component] + + TIF --> FIN2((FIN)) + + PB --> BIN3((BIN)) + + CB --> FIN3((FIN)) + + RB --> FIN4((FIN)) + + LB --> BIN4((BIN)) + + CBOX --> BIN5((BIN)) + + SL --> FIN5((FIN)) + + TC --> FIN6((FIN)) + TC --> TIN((TIN)) + TC --> ST[Sensitive text] + + ST --> FIN7((FIN)) + +``` + +Figure 20/T.107: Element relationships within the dialogue box. This diagram shows a 'Dialogue box' at the top with arrows pointing to a vertical list of components: Separator, Frame, Graphic output area, Text area, Text input field, Push button, Check box, Radio button, List box, Combo box, Slider, and Sensitive area. The 'Graphic output area' has arrows pointing to 'VIN' and 'BIN'. The 'Text area' has an arrow pointing to 'FIN'. The 'Text input field' has an arrow pointing to 'FIN'. The 'Push button' has an arrow pointing to 'BIN'. The 'Check box' has an arrow pointing to 'FIN'. The 'Radio button' has an arrow pointing to 'FIN'. The 'List box' has an arrow pointing to 'BIN'. The 'Combo box' has an arrow pointing to 'BIN'. The 'Slider' has an arrow pointing to 'FIN'. The 'Sensitive area' has no outgoing arrows. The 'Text area' also has an arrow pointing to a 'Text component' box. The 'Text component' box has arrows pointing to 'FIN', 'TIN', and 'Sensitive text'. The 'Sensitive text' box has an arrow pointing to 'FIN'. The 'Dialogue box' also has an arrow pointing to 'BIN'. + +T0823970-95/d20 + +FIGURE 20/T.107 +Element relationships within the dialogue box + +A text title may be given to the Dialogue Box which shall be displayed in its first row. The title height equals 1/32 NDC. + +The Dialogue Box can be provided with a border area which should be equal to one character position. When present, this border shall be included in the dimensions defined by the VEMMI application. When a border is requested, a frame shall be drawn by the terminal. This frame drawing is terminal dependent (it should not be wider than 1/160 NDC). + +The object origin of the Dialogue Box is the top left corner of the box rectangle, independent whether the box has a title or not. The components are positioned relatively to this point for Dialogue Boxes that do not have a text title. In the case of boxes with a text title, this point is moved downwards by a distance corresponding to the titles height and the borders width and horizontally by the distance equal to the border width. + +The background area of the Dialogue Box is the rectangle defined by the box dimensions, except the title bar and the border. The background can be coloured uniform or with a data content. + +### Behaviour + +The user can activate any component with a pointing device or with the keyboard. If the user activates the components with the keyboard keys providing the functionality “Previous” and “Next”, the order of activation should correspond to the reception order of the components of the Dialogue Box. + +### Interactive functionality + +- Moving. + +### Visual aspect (see Figure 21) + +![Diagram of a Dialogue box showing its visual structure and components.](677bcb564410628b8b966ad87b394888_img.jpg) + +The diagram illustrates the visual structure of a Dialogue box. It is a rectangular window with a title bar at the top. The main content area is divided into several sections: + +- Title bar:** A black bar at the top of the window. +- Buttons:** Two buttons labeled "OK" and "Cancel" are located in the top right corner. +- Input fields:** A "Drop down list box item 7" and a text field containing "177" are located in the top left. +- Check boxes:** A vertical list of six check boxes labeled "Check box 1" through "Check box 6" is located on the left side. "Check box 4" is checked. +- Radio button group:** A group of three radio buttons labeled "Radio button 1", "Radio button 2", and "Radio button 3" is located on the right side. "Radio button 2" is selected. +- Monitor:** A small icon of a monitor is located in the bottom right corner. +- Presentation area:** A label "Presentation area" is located in the bottom right corner. + +The diagram also includes labels for the box's dimensions and position: + +- XPos:** The horizontal position of the box. +- YPos:** The vertical position of the box. +- Width:** The width of the box. +- Height:** The height of the box. +- DDA:** The Display Data Area. +- Frame:** The border of the box. + +Diagram of a Dialogue box showing its visual structure and components. + +T0815610-94/d21 + +FIGURE 21/T.107 + +#### Dialogue box + +### Attributes + +- **XPos:** This attribute carries the horizontal position of the element in NDC. +- **YPos:** This attribute carries the vertical position of the element in NDC. +- **Width:** This attribute carries the width of the object. +- **Height:** This attribute carries the height of the object. +- **NoBorder:** No border shall be drawn. +- **Title:** This attribute carries the title of the object. The title shall be displayed in the first row of the object. + +- FirstActive: This attribute carries the CIN of the component which is active by default, the first time the object is opened. +- Modal: The element shall be modal. +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. +- StoreInitialValues: The terminal shall store the initial values of the component at the time of the object creation. If a local action “restore initial values” is applied, these stored values shall be restored. +- Maximizable: The object is maximizable. +- Colour: Colour index of the background. +- BIN: Bitmap identification number to fill the Dialogue Box Background. +- DispType: Specifies the display mode of the background bitmap: centred, stretched (default) or tiled. + +### 7.6.1 Composition + +#### 7.6.1.1 The Separator component + +##### Description + +The Separator is either a horizontal or a vertical solid line used to separate different areas within a Dialogue Box. + +##### Behaviour + +The Separator shall be inaccessible. + +##### Interactive functionality + +- None. + +**Visual aspect** (see Figure 22) + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Vertical: The element shall be drawn vertically. +- Height: This attribute carries the height of the component. It is only applicable to vertical Separators. +- Width: This attribute carries the width of the component. It is only applicable to horizontal Separators. +- Closed: The element shall be in the closed state. +- Colour: Colour index. + +#### 7.6.1.2 The Frame component + +##### Description + +A Frame consists of four solid lines which visually separate a rectangular area of the Dialogue Box. + +##### Behaviour + +The Frame shall be inaccessible. + +##### Interactive functionality + +- None. + +![Diagram of a dialog box layout with various controls and dimensions.](15de63f0b5df62e6ab9164f2a72e2e33_img.jpg) + +The diagram illustrates a dialog box layout. At the top is a black title bar labeled "Dialogue box". Below it, a vertical separator line divides the main area. On the left side of the separator, there are three radio buttons labeled "Radio button 1", "Radio button 2" (which is selected), and "Radio button 3". On the right side, there are three check boxes labeled "Check box". A horizontal separator line is located below the check boxes. Dimensions are indicated: "XPos" for the horizontal position of the separator, "YPos" for the vertical position of the title bar and the horizontal separator, "Height" for the vertical extent of the main area, and "Width" for the horizontal extent of the main area. A label "Separator vertical" points to the vertical line, and "Separator horizontal" points to the horizontal line. + +T0824340-95/d22 + +Diagram of a dialog box layout with various controls and dimensions. + +FIGURE 22/T.107 + +###### Separator + +Visual aspect (see Figure 23) + +![Diagram of a frame titled with a text presentation area.](343e05a9fd8a8c8743428fa4ae6e2736_img.jpg) + +The diagram shows a frame titled with a text presentation area. The frame has a black title bar at the top. Inside the frame, there is a rectangular area labeled "Presentation area". This area is titled "Monitor" and contains an icon of a computer monitor and a printer. The frame is labeled "Frame" on the right side. Dimensions are indicated: "XPos" for the horizontal position of the presentation area, "YPos" for the vertical position of the title bar, "Width" for the horizontal extent of the presentation area, and "Height" for the vertical extent of the presentation area. + +T0815630-94/d23 + +Diagram of a frame titled with a text presentation area. + +FIGURE 23/T.107 + +###### Frame titled with a text presentation area + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Width: This attribute carries the width of the component. +- Height: This attribute carries the height of the component. +- Closed: The element shall be in the closed state. +- Colour: Colour index. + +#### 7.6.1.3 The Text Presentation Area component + +##### Description + +The Text Presentation Area is an area intended to present text data to the user. Basically, this element is used to present text that fits in one window (the space defined by one text area component) or to present large text data where the user has to use scrolling tools in order to navigate through the text. + +The Text Presentation Area has its starting location in the top left corner of the rectangle defined by the component and the text is displayed row by row from the left to the right. The text content can contain “In-Text” attributes to switch between different attribute fonts and to define “sensitive text strings”. The “In-Text” attributes can appear multiple, in any order, and they are evaluated during the display operation sequentially and on the basis of structural information contained in text components (“previous, next” attributes). + +##### Scrolling, Border, Title + +If the space needed for the presentation of the data is bigger than the space allocated for the component, vertical scrolling tools shall be provided by the terminal application. The terminal may present: + +- scrolling tools next to the right side of the area; +- reduced scrolling tools as buttons overlapping the area; +- cursor keys that provide the scrolling functionality. + +The space needed for the scrolling tools is included in the overall dimensions of the component. + +The component can be provided with a border area. When present, the border shall be included in the overall dimensions of the component. When a border is requested a frame shall be drawn by the terminal. The frame drawing is terminal dependent. It should not be wider than 1/160 NDC. If scrolling tools are provided next to the right side of the component, the border shall be extended to include them visually in the box. + +##### Maximize operation + +The size of the Dialogue Box can be changed by the user with the scrolling tools provided by the local Graphical User Interface (GUI) and via a defined maximize button. The recommended strategy is described in 7.1.5. These are default recommendations. If the attribute “NoFormat” is selected for the component, the following applies: + +- a vertical increase should not change the text form, no additional text should be added; +- a vertical decrease should clip the text on the new border; +- a horizontal increase should add new text lines; +- a horizontal decrease should clip the text. + +##### Interactive functionality + +- Activation and validation of sensitive text, defined via in-text attributes. + +NOTE – To transfer a large amount of text data, it is recommended not to use the direct text definition but to use the Text Resource object and transmit the data using the VEMMI resource transfer. + +##### Visual aspect (see Figure 24) + +![Diagram of a text presentation area with dimensions and content.](a9159a006d67a834a7b1a771c18191cc_img.jpg) + +The diagram illustrates a text presentation area within a terminal window. A large rectangle represents the area, with a thick black bar at the top. Dimensions are indicated by lines and labels: 'XPos' for the horizontal position of the top-left corner, 'YPos' for the vertical position, 'Width' for the horizontal extent of the text block, and 'Height' for the vertical extent. The text inside the area reads: 'The enclosed CONDITIONS are an essential part of the contract. To apply for participation in the **Never Comeback Conference**, please transfer the participation fee as soon as possible. More information in the detailed *Conditions of Participation*.' The phrase 'Conditions of Participation' is enclosed in a dotted-line box. The identifier 'T0824350-95/d24' is located at the bottom right of the diagram. + +Diagram of a text presentation area with dimensions and content. + +FIGURE 24/T.107 +Text presentation area + +##### Attribute + +- CIN: This attribute carries the Component Identification Number. +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Width: This attribute carries the width of the component. +- Height: This attribute carries the height of the component. +- NoScrollingTools: No scrolling tools shall be drawn by the terminal. +- Format: A maximization of the dialogue box shall use the limited formatting rules described above. +- NoBorder: No Border shall be drawn to frame the element. +- InitialFnt: FIN of the attribute font to be applied on the first text. + +- Autoscroll: A modification of a component referenced by the text area leads to an immediate display of this modified component. +- InText: Text content possibly including in-text attributes, and references to font objects. +- TextCompRef: Reference to a text component. +- Closed: The element shall be in the closed state. + +#### 7.6.1.4 The Text component + +##### Description + +This component is used to split large text data in units (text components) and to define the necessary structural information (concatenation of the text components) in order to be displayed in a text area. This structural information are references to the previous and next text components, defined with the attributes “NextText” and “PreviousText”. + +##### Display Concept + +The components are not necessarily of the same length. During the display of concatenated text components, the user should have the impression of a continuous text. The continuity should not be interrupted by a switch from one component to the other. Vertical scrolling capabilities, on a row-by-row and page-by-page basis, shall be offered within consecutive components. This display continuity is interrupted in two cases: + +- A component contains no further concatenation, no “NextText” during a forward scrolling or no “PreviousText” during a backward scrolling. The display does not continue because the just displayed text pertains to a topic which has reached its logical end. Figure 29 shows two sequences of concatenated components: CINs 7,8,9 and CIN 17. +- “Jumps” due to the validation of sensitive text as part of the displayed components or other interactive components of the dialogue box. Sensitive text attribute can contain as a local action an element specific command, e.g. “open component of parent object”. The referenced parent component is a text component which will be displayed in the starting position and not consecutively to the last displayed component. This effect is shown in Figures 27 and 28. + +The text to be displayed is contained in the component definition, in another referenced text component or in a referenced text resource object. If such a resource object is not available in the terminal, it can be requested from the host application with the command VEMMI\_Object\_Retransmission and the Rule B shall be applied (see 5.3.2). Such a request might be initiated due to a forward scroll to data which is not yet in the terminal, but in general there is no direct relation between the scrolling action and the object retransmission request, because the terminal keeps the already received objects. + +NOTE – To transfer a large amount of text data, it is recommended not to use the direct text definition but to use the Text Resource object and transmit the data using the VEMMI resource transfer. + +**Visual aspect** (see Figures 25 to 28) + +![Screenshot of a user interface showing a text area with scroll bars. The text area contains instructions under the heading 'General notes on operation' and 'Basic settings'. A label 'Text area' points to the right side of the scroll bar.](b37e60360a03806dc8c1bbfae6aef88a_img.jpg) + +General notes on operation + +Basic settings + +On switching on after a longer period without mains power, all selectable functions are disabled and all controls set to middle or zero. The loudspeaker outputs remain connected to the power amplifiers. Displays: e.g. 87. V40 **"LS 1" "LS 2"**. To operate use **>loudn.<** to select loudness compensated volume (display: loudn.) and disable unoccupied loudspeaker outputs using "LS 1" or "LS 2" on the R4. Using the remote control unit, press **"speaker"** (display: e.g. SP1/2) and the press "1" or "2" to enable or disable the corresponding loudspeaker output. + +Text area + +Screenshot of a user interface showing a text area with scroll bars. The text area contains instructions under the heading 'General notes on operation' and 'Basic settings'. A label 'Text area' points to the right side of the scroll bar. + +T0823990-95/d25 + +FIGURE 25/T.107 + +**A text area with text component(s), scroll bars and sensitive texts (Attribute "NoFormat" is not set). Now, the user becomes active and scrolls downward ...** + +![Screenshot of a user interface showing a text area with scroll bars. The text area contains instructions under the heading 'e.g. 87. V40' and 'Tuning'. The scroll bar is positioned lower than in the previous screenshot, indicating scrolling.](cd5470ebc42e0b621378f0fa519c8e83_img.jpg) + +e.g. 87. V40 **"LS 1" "LS 2"**. To operate use **>loudn.<** to select loudness compensated volume (display: loudn.) and disable unoccupied loudspeaker outputs using "LS 1" or "LS 2" on the R4. Using the remote control unit, press **"speaker"** (display: e.g. SP1/2) and the press "1" or "2" to enable or disable the corresponding loudspeaker output. + +Tuning + +On the unit, use the **"fm" or "am"** buttons to select FM or AM wavebands. Display: e.g. 94.40 MHz, | (center tuning), ||||| (field strength display), stereo, if a stereo station is being received with adequate quality. Using the remote control unit, press "fm" to select FM. + +Screenshot of a user interface showing a text area with scroll bars. The text area contains instructions under the heading 'e.g. 87. V40' and 'Tuning'. The scroll bar is positioned lower than in the previous screenshot, indicating scrolling. + +T0823560-95/d26 + +FIGURE 26/T.107 + +**... in addition he/she enlarges the window on both directions, ...** + +e.g. 87. V40 **"LS 1" "LS 2"** . To operate use **>loudn.<** to select loudness compensated volume (display: loudn.) and disable unoccupied loudspeaker outputs using "LS 1" or "LS 2" on the R4. + +Using the remote control unit, press **"speaker"** (display: e.g. SP1/2) and the press "1" or "2" to enable or disable the corresponding loudspeaker output. + +Tuning + +On the unit, use the **"fm" or "am"** buttons to select FM or AM wavebands. Display: e.g. 94.40 MHz, | (center tuning), ||||| (field strength display), stereo, if a stereo station is being received with adequate quality. + +Using the remote control unit, press "fm" to select FM reception (repeating toggles between FM and AM). + +Station search + +To tune to a particular station, activate search on the unit by pressing "autotune+" or "autotune-". + +Using the remote control unit, press ">>" or "<<". + +T0823570-95/d27 + +FIGURE 27/T.107 +... and finally, clicks on the hot spot "speaker" + +**"speaker"** + +Activates buttons "1" and "2" (for 3 seconds) to switch the loudspeaker pairs connected with terminals **"LS 1" and "LS 2"** to amplifier output. Display SP1/- and SP2/- with the corresponding loudspeaker symbols. + +Attention ! Care must be taken to ensure that the phases are correctly connected for the left and right speakers in a pair and for the two pairs of loudspeakers (if they are to be operated in the same room). The black terminals are grounded. + +T0823580-95/d28 + +FIGURE 28/T.107 +The "speaker" text is displayed + +A possible component architecture for the display sequence shown in Figures 25 to 29 can be the following (the in-text attributes are not listed): + +| | | +|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------------------------------------------------------------| +|

General notes on operation

Basic settings

On switching on after a longer period without mains power, all selectable functions are disabled and all controls set to middle or zero. The loudspeaker outputs remain connected to the power amplifiers. Displays: e.g. 87. V40 "LS 1" "LS 2". To operate use >loudn.< to select loudness compensated volume (display: loudn.) and disable unoccupied loudspeaker outputs using "LS 1" or "LS 2" on the R4.

Using the remote control unit, press "speaker" (display: e.g. SP1/2) and the press "1" or "2" to enable or disable the corresponding loudspeaker output.

|

Text component

CIN: 7

Next text: 8

| +|

Tuning

On the unit, use the "fm" or "am" buttons to select FM or AM wavebands. Display: e.g. 94.40 MHz, (centre tuning), (field strength display), stereo, if a stereo station is being received with adequate quality.

Using the remote control unit, press "fm" to select FM reception (repeating toggles between FM and AM).

|

Text component

CIN: 8

Previous text: 7

Next text: 9

| +|

Station search

To tune to a particular station, activate search on the unit by pressing "autotune+" or "autotune-".

Using the remote control unit, press ">>" or "<<".

The search, with automatic muting, continues in the selected direction until the next station with adequate reception quality and centre tuning position is located.

|

Text component

CIN: 9

Previous text: 8

| +|

"speaker"

Activates buttons "1" and "2" (for 3 seconds) to switch the loudspeaker pairs connected with terminals "LS 1" and "LS 2" to amplifier output. Display SP1/- and SP-/- with the corresponding loudspeaker symbols.

Attention! Care must be taken to ensure that the phases are correctly connected for the left and right speakers in a pair and for the two pairs of loudspeakers (if they are to be operated in the same room). The black terminals are grounded.

|

Text component

CIN: 17

| + +FIGURE 29/T.107 + +##### Text component architecture + +The local interactivity can be implemented by the correct cooperation of the local actions (LocActVal parameter) which are part of the sensitive text and other interactive elements of the dialogue box. In the example case, the user can skip from the text of Figure 27 to Figure 25 with the Sensitive Text "Speaker" if the Sensitive Text contains the local action "open component 7". + +##### Attributes + +- CIN: Component Identification Number. +- PreviousText: CIN of the backward concatenated text component. +- CurrentText: Text definition, including references to font resource objects, text resource objects and sensitive text components. +- NextText: CIN of the forward concatenated text component. + +#### 7.6.1.5 The Sensitive Text Component + +These components define the activation and validation operations for sensitive text strings. These are part of text components. + +##### Visual aspect + +See 7.6.1.4. + +##### Attributes + +- CIN: Component Identification Number. +- NotAccessible: The element shall not be accessible. +- LocActAct: Specifies the local actions which are associated to the component and triggered by its activation. +- LocActVal: Specifies the local actions which are associated to the component and triggered by its validation. + +#### 7.6.1.6 The Graphic Output Area component + +##### Description + +The Graphic Output Area is a rectangle to display graphical data (bitmaps, videotex data, etc.). A bitmap is referenced via a BIN. Three different display modes exist: the bitmap can be centred in the Graphic Output Area, it can be stretched to cover the whole area or it can be tiled. In any case the bitmap shall not exceed the space reserved with this component. If the referenced bitmap does not exist while the component is opened, it has no visual effect. + +Videotex data are referenced via a VIN. In any case the Videotex data shall not exceed the space reserved with this component. If the referenced Videotex data content does not exist while the component is opened, it has no visual effect. + +##### Behaviour + +It is inaccessible. + +##### Interactive functionalities + +- None. + +**Visual aspect** (see Figure 30) + +##### Attributes + +- CIN: Component Identification Number. +- XPos: Horizontal position of the top left corner of the bitmap rectangle. +- YPos: Vertical position of the top left corner of the bitmap rectangle. +- Width: Width of the bitmap rectangle. +- Height: Height of the bitmap rectangle. +- Closed: The element shall be in the closed state. +- DispType: Specifies the display mode of the bitmap: centred, stretched (default) or tiled. +- BIN: Bitmap Identification Number. +- VIN: Videotex Identification Number. + +#### 7.6.1.7 The Push Button component + +##### Description, behaviour, interactive functionality + +See 7.4.1.1. + +![Diagram of a dialog box containing a frame with a world map bitmap.](e2dad48ec062e71202459a9ab82261e4_img.jpg) + +The diagram illustrates a user interface element. A large rectangle represents a 'Dialogue box'. At the top of this box is a black horizontal bar labeled 'Dialogue box'. Inside the main area of the dialogue box is a smaller rectangle labeled 'Frame'. This frame contains a grayscale world map. Dimension lines indicate the 'XPos' (horizontal position) and 'YPos' (vertical position) of the dialogue box. The 'Frame' itself has dimension lines for its 'Width' and 'Height'. A label 'Frame' with a pointer line identifies the frame rectangle. + +T0824360-95/d29 + +Diagram of a dialog box containing a frame with a world map bitmap. + +FIGURE 30/T.107 +Frame and a bitmap + +**Visual aspect** (see Figure 31) + +![Diagram of a dialog box containing an OK push button.](0931f3e098bd4539041de11c50cec2d2_img.jpg) + +The diagram illustrates a user interface element. A large rectangle represents a 'Dialogue Box'. At the top of this box is a black horizontal bar labeled 'Dialogue Box'. Inside the main area of the dialogue box is a smaller rectangle labeled 'OK'. This rectangle contains the text 'OK'. Dimension lines indicate the 'XPos' (horizontal position) and 'YPos' (vertical position) of the dialogue box. The 'OK' button has dimension lines for its 'Width' and 'Height'. A label 'Mnemonic' with a pointer line identifies the 'OK' text. + +T0824370-95/d30 + +Diagram of a dialog box containing an OK push button. + +FIGURE 31/T.107 +Push button + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Width: This attribute carries the width of the component. +- Height: This attribute carries the height of the component. +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. +- BIN: The BIN of the component. +- Text: The text content of the component. +- LocActAct: This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- LocActVal: This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +#### 7.6.1.8 The Text Input Field component + +##### Description + +The Text Input Field is composed of two items: + +- the text label; +- the input area. + +An attribute font can be associated to the text label. The input area has its starting location immediately after the text label. The type of the input data can be specified by the application. The following predefined types are available: + +- any text character; +- alphabetic (A..Z, a..z, diacritical characters); +- numeric (0..9, +, -, comma, dot, space); +- alphanumeric (alphabetic, numeric). + +An attribute of the Text Input Field specifies whether the user inputs are echoed or not. The VEMMI application can define one character to echo all user inputs. + +A mnemonic key can be used to activate the Text Input Field (see 7.1.7). + +##### Behaviour + +If the space allocated for the input area in a one line Text Input Field is not sufficient to display all characters entered by the user, the input area shall offer horizontal scrolling facilities. If the space, allocated for the input area in a Text Input Field with more than one line, is not sufficient to display all characters entered by the user, the input area shall offer vertical scrolling facilities. In order to display all possible characters, it is recommended to give enough space for user inputs. If the maximum number of the input characters is reached this should be indicated to the user. + +##### Constraints + +The maximum length of the text label is limited to the first line of the Text Input Field component width. For one line input fields the label is placed in front of the input area and left aligned, while the input area is aligned to the right side. For multiline Text Input Fields it is placed in the top row and shall be left aligned. There is no space reserved for the text label if the attribute TextLabel is not present. + +##### Interactive functionality + +- activation; +- scrolling; +- local editing functionality of the input area (terminal dependent). + +**Visual aspect** (see Figure 32) + +![Diagram illustrating the visual aspect of a text input field. It shows a large rectangular container with a thick black border. Inside, there are two examples of text input fields. The top example consists of a 'Text label:' followed by a 'Text input I' box. The bottom example consists of a 'Text label:' followed by a larger box containing the text 'Text input in a text Input field that covers several rows I'. Dimension lines indicate 'XPos' for the horizontal position, 'YPos' for the vertical position, 'Width' for the width of the input field, and 'Height' for the height of the input field. A reference code 'T0824380-95/d31' is located at the bottom right of the diagram area.](08ccf644bfe3417a310e15f03a536ff8_img.jpg) + +Diagram illustrating the visual aspect of a text input field. It shows a large rectangular container with a thick black border. Inside, there are two examples of text input fields. The top example consists of a 'Text label:' followed by a 'Text input I' box. The bottom example consists of a 'Text label:' followed by a larger box containing the text 'Text input in a text Input field that covers several rows I'. Dimension lines indicate 'XPos' for the horizontal position, 'YPos' for the vertical position, 'Width' for the width of the input field, and 'Height' for the height of the input field. A reference code 'T0824380-95/d31' is located at the bottom right of the diagram area. + +FIGURE 32/T.107 + +##### **Text input field** + +##### **Attributes** + +- **CIN:** This attribute carries the Component Identification Number. +- **XPos:** This attribute carries the horizontal position of the element in NDC. +- **YPos:** This attribute carries the vertical position of the element in NDC. +- **Width:** This attribute carries the width of the component. +- **Height:** This attribute carries the height of the component. +- **Closed:** The element shall be in the closed state. +- **NotAccessible:** The element shall not be accessible. +- **MaximTxt:** Local maximization can maximize the text of the component proportionally. +- **DefValue:** This attribute carries the default value for the component. +- **TextLabel:** This attribute carries the text label of the component. +- **LabelFont:** Specifies the FIN for the text label. +- **InputType:** This attribute specifies which type of user inputs shall be accepted by the component. +- **Echo:** This attribute specifies which type of echo shall be made on user inputs. +- **EchoChar:** This attribute carries the character that shall be displayed to echo user inputs. + +- **MaxChar:** This attribute carries the maximum number of characters the user can enter in one line. +- **MaxLine:** This attribute carries the maximum number of lines the user can enter in a multiline input field. +- **Multiline:** Indicates a multiline input field. +- **InputTransformation:** The attribute specifies if the terminal shall convert the characters entered by the user to upper case characters, to lower case characters or if no conversion shall be done. +- **LocActAct:** This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- **LocActVal:** This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +#### 7.6.1.9 The Check Box component + +##### Description + +The Check Box component is composed of two items: + +- the text label item; +- the check item. + +A mnemonic key can be used to activate the component (see 7.1.7). + +The check item shall support two different choices, visually identifiable, representing the two possible values marked or unmarked. The space allocated for the component shall include, in its dimensions, the space needed to represent this check item. + +##### Behaviour + +A Check Box acts like a switch. When switched by the user, its value changes from unmarked to marked or from marked to unmarked. The value of Check Boxes is independent of the value of any other components. + +##### Interactive functionality + +- activation; +- switch between the values marked and unmarked; +- validation. + +**Visual aspect** (see Figure 33) + +##### Attributes + +- **CIN:** This attribute carries the Component Identification Number. +- **XPos:** This attribute carries the horizontal position of the element in NDC. +- **YPos:** This attribute carries the vertical position of the element in NDC. +- **Width:** This attribute carries the width of the component. +- **Height:** This attribute carries the height of the component. +- **Closed:** The element shall be in the closed state. +- **NotAccessible:** The element shall not be accessible. +- **TextLabel:** This attribute carries the text label of the component. +- **LabelFont:** FIN of the label. +- **DefMarked:** The default value of the element shall be marked. +- **LocActAct:** This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- **LocActVal:** This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +![Diagram of a Dialogue box containing three check boxes. The box has a title bar 'Dialogue box'. Dimensions are indicated: XPos (horizontal position), YPos (vertical position), Width (horizontal size), and Height (vertical size). Inside, three check boxes are listed: 'Check box 1' (unchecked), 'Check box 2' (checked), and 'Check box 3' (checked).](f78d2e126f00fcc5d8d9797ca410cc09_img.jpg) + +The diagram illustrates a 'Dialogue box' with a title bar. It shows the box's position (XPos, YPos) and dimensions (Width, Height). Inside the box, three check boxes are displayed, each with a label: 'Check box 1' (unchecked), 'Check box 2' (checked), and 'Check box 3' (checked). The check boxes are arranged vertically. The diagram is labeled 'T0815680-94/d32' in the bottom right corner. + +Diagram of a Dialogue box containing three check boxes. The box has a title bar 'Dialogue box'. Dimensions are indicated: XPos (horizontal position), YPos (vertical position), Width (horizontal size), and Height (vertical size). Inside, three check boxes are listed: 'Check box 1' (unchecked), 'Check box 2' (checked), and 'Check box 3' (checked). + +FIGURE 33/T.107 +**Check box** + +#### 7.6.1.10 The Radio Button component + +##### Description + +The Radio Button component is composed of two items: + +- the text label item; +- the check item. + +A mnemonic key can be used to activate the component (see 7.1.7). + +The check item shall support two different choices, visually identifiable, representing the two possible values marked and unmarked. The space allocated for the component shall include, in its dimensions, the space needed to represent this check item. + +Radio Buttons are typically used in groups to provide a single-choice field. + +##### Behaviour + +No more than one Radio Button shall be marked in a Radio Button group at a given time. The attempt to mark a second Radio Button shall cause the unmarking of the previously marked Radio Button, whatever its state (opened, closed, accessible, inaccessible) within the application may be. + +##### Interactive functionality + +- activation; +- switch between the values marked and unmarked; +- validation. + +**Visual aspect** (see Figure 34) + +![Diagram of a Dialogue Box containing two radio button groups.](bf316d14a760a28869460fd9b0c9f616_img.jpg) + +The diagram illustrates a 'Dialogue Box' with a black title bar. Inside, there are two distinct frames, each containing a radio button group. The first frame, labeled 'Radio button group 1', contains three radio buttons: 'Radio button 1' (unselected), 'Radio button 2' (selected, indicated by a black dot), and 'Radio button 3' (unselected). The second frame, labeled 'Radio button group 2', contains three radio buttons: 'Radio button 4' (unselected), 'Radio button 5' (unselected), and 'Radio button 6' (selected, indicated by a black dot). Dimension lines indicate the 'XPos' and 'YPos' of the dialogue box, the 'Width' and 'Height' of the first frame, and the 'Width' of the second frame. The text 'T0815690-94/d33' is located at the bottom right of the diagram. + +Diagram of a Dialogue Box containing two radio button groups. + +FIGURE 34/T.107 + +###### **Radio buttons with a frame and a text presentation area** + +##### **Attributes** + +- **CIN:** This attribute carries the Component Identification Number. +- **XPos:** This attribute carries the horizontal position of the element in NDC. +- **YPos:** This attribute carries the vertical position of the element in NDC. +- **Width:** This attribute carries the width of the component. +- **Height:** This attribute carries the height of the component. +- **Closed:** The element shall be in the closed state. +- **NotAccessible:** The element shall not be accessible. +- **TextLabel:** This attribute carries the text label of the component. +- **LabelFont:** FIN of the label. +- **Group:** This attribute carries the identifier of the Radio Button group. Only one Radio Button in a group can be marked at one specific time. +- **DefMarked:** The default value of the element shall be marked. +- **LocActAct:** This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- **LocActVal:** This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +#### 7.6.1.11 The List Box component + +##### Description + +The List Box component is a rectangular area in which a list of text items is offered to the user for choice. If the total number of items exceeds the number of presented items, scrolling facilities shall be offered to the user through dedicated scrolling controls. When the entire list is visible the scrolling controls may be invisible. In this case, the space allocated for the component shall include in its dimensions the space needed to represent the scrolling facilities. The tools to provide the scrolling functionality are terminal dependent (vertical scrollbar, buttons, etc.). + +Small icons may be added to the list items in order to visually emphasize their meaning. The referenced bitmap can be resized to fit to the local List Box representation. + +The whole list is composed of list items. There shall be no CR + LF within the text content of a list item. If the attribute sorted is selected, the list items should be sorted in their alphabetical order. If sorted is not selected, the list shall be presented in the ascending order of the list item indices. However, the correspondence between the list items and the indices is always maintained. + +##### Behaviour + +When the List Box is active the terminal shall offer shifting facilities to the user. A List Box contains a list of items that the user can scroll through and select from. Single or multiple choice can be made by the user, depending on the list attributes. + +There may be local actions associated to each List Box item. Additionally, the List Box may also have local actions associated. Upon activation and validation of a List Box item, the local actions associated to the list box item shall be executed. If there is no local action associated to the selected item, the local action associated to the List Box itself shall be executed. In this case, any OIN appearing in element specific commands of the List Box component is incremented by the value of the list index of the list box item. + +A List Box with multiple choice cannot be validated. + +##### Interactive functionality + +- activation; +- single or multiple choice; +- validation (single choice); +- scrolling; +- shifting. + +##### Visual aspect (see Figure 35) + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Width: This attribute carries the width of the component. +- Height: This attribute carries the height of the component. +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. +- DefItem: This attribute carries the index of the list item that is selected by default when the component is opened for the first time. +- Sorted: The list items are presented sorted in alphabetical order. +- MultipleChoice: The element allows multiple choices. +- LocActAct: This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- LocActVal: This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +![Diagram of a List box within a Dialogue Box. The Dialogue Box has a title bar and a main area. Inside, a List box contains 11 items, labeled 'List box item 6' through 'List box item 16'. Item 6 is highlighted. A vertical scrollbar is on the right of the list. Dimensions are indicated: XPos (horizontal position), YPos (vertical position), Width (list box width), and Height (list box height). A small icon is visible next to 'List box item 9'.](0adfaa8c2562a9fe3a8a96165d7d59a3_img.jpg) + +T0824390-95/d34 + +Diagram of a List box within a Dialogue Box. The Dialogue Box has a title bar and a main area. Inside, a List box contains 11 items, labeled 'List box item 6' through 'List box item 16'. Item 6 is highlighted. A vertical scrollbar is on the right of the list. Dimensions are indicated: XPos (horizontal position), YPos (vertical position), Width (list box width), and Height (list box height). A small icon is visible next to 'List box item 9'. + +FIGURE 35/T.107 + +###### List box + +###### List item attributes + +- **ListIndex:** This attribute carries the index of the next list item in the component description. It allows in a modify command the modification of a specific list item. The list indices shall be defined in an ascending order. The list indices may not be consecutive in order to allow easy updating of the list (inserting of list items). The terminal shall present a consecutive list to the user, sorted by the ascending value of the list indices corresponding to the list text. If in modify command a list index for a list item is used which is already existing, then the existing list item is replaced. If in a modify command a list index of a list item is used that is not existing in the terminal, the new list item shall be added. If in a modify command a list index is referenced which is already existing but in the modify command the corresponding attribute “ListText” is missing, the referenced list item on the terminal shall be deleted. +- **ListText:** This attribute carries the text content of a list item. +- **BIN:** The BIN of the component. +- **ItemActAct:** This attribute carries the code for the local action which is associated to the item and triggered by its activation. +- **ItemActVal:** This attribute carries the code for the local action which is associated to the item and triggered by its validation. + +#### 7.6.1.12 The Combination Box component + +##### Description + +The Combination Box is composed of two parts: + +- a single choice List Box; +- a one line text field located at the top of the list. + +If the total number of items exceeds the number of presentable items, scrolling facility shall be offered to the user through dedicated scrolling facilities. In this case, the space allocated for the component shall include in its dimensions the space needed to represent the scrolling facilities. The tools to provide the scrolling functionality are terminal dependent (vertical scrollbar, buttons, etc.). + +Small icons may be added to the list items in order to visually emphasize their meaning. The referenced bitmap can be resized to fit to the local Combination Box representation. + +The whole list is composed of list items. There shall be no CR + LF within the text content of a list item. If the attribute sorted is selected, the list items should be sorted in their alphabetical order. If sorted is not selected the list shall be presented in the ascending order of the list item indices. However, the correspondence between the list items and the indices is always maintained. + +A variation of the Combination Box is a drop down Combination Box. It is composed of a Combination Box and a Push Button. Only the text field and the Push Button are displayed until the user validates the associated Push Button. The validation of the Push Button causes the display of the associated List Box. + +##### **Behaviour** + +When the List Box is active the terminal shall offer shifting facilities to the user. A Combination Box contains a list of items that the user can scroll through and select from to complete the text field. A parameter of the Combination Box specifies if the text field is editable or not. If the text field is editable, the user can type text directly into the text field. A parameter of the component specifies if the text entered by the user shall match one of the items contained in the list. + +There may be local actions associated to each List Box item. Additionally, the Combination Box may also have local actions associated. Upon activation and validation of a List Box item, the local actions associated to the list box item shall be executed. If there is no local action associated to the selected item, the local action associated to the Combination Box itself shall be executed. In this case, any OIN appearing in element specific commands of the List Box component is incremented by the value of the list index of the listbox item. + +If the Combination Box is designed to be a drop down Combination Box, the validation of the Push Button shall switch between the display and the hide of the List Box. + +##### **Interactive functionality** + +- activation; +- single selection; +- validation; +- scrolling; +- editing. + +##### **Visual aspect** (see Figure 36) + +##### **Attributes** + +- CIN: This attribute carries the Component Identification Number. +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Width: This attribute carries the width of the component. +- Height: This attribute carries the height of the component. +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. + +- **DefItem:** This attribute carries the index of the list item that is selected by default when the component is opened for the first time. +- **NoEdit:** The text field of the component shall not be editable. +- **NoConsistency:** This attribute is applied if “NoEdit” is not set. It indicates that the text entered by the user can be any text string, not necessarily one of the defined text items. +- **MaxChar:** This attribute carries the maximum number of characters the user can enter in the component. It shall only be present if the “EditableInput” Parameter is set true. +- **NoDropDown:** The element shall not be dropped down. +- **NotSorted:** The list items are presented not sorted in alphabetical order. +- **LocActAct:** This attribute carries the code for the local action which is associated to the component and triggered by its activation. +- **LocActVal:** This attribute carries the code for the local action which is associated to the component and triggered by its validation. + +![Diagram of a combination box within a dialogue box. The dialogue box has a title bar 'Dialogue box'. Inside, there are two list boxes. The left list box is titled 'List box item 10 I' and contains items 6 through 16. The right list box is titled 'List box item 8 I' and contains items 4 through 11. Both list boxes have a width and height dimensioned. The right list box has a drop-down arrow button next to it. A text label 'Drop down combination box before the drop down push button is validated' is positioned above the right list box. The diagram also shows XPos and YPos dimensions for the list boxes and the dialogue box.](66fb62ebfc68240e7523d7d1ac7f1656_img.jpg) + +The diagram illustrates a UI 'Dialogue box' containing two variations of a 'Combination box'. +On the left, a large list box is shown with dimensions 'Width' and 'Height'. It contains a scrollable list of items from 'List box item 6' to 'List box item 16'. 'List box item 10' is highlighted. Above the list is a text field containing 'List box item 10 I'. +On the right, a smaller combination box is shown. Above it is the text: 'Drop down combination box before the drop down push button is validated'. This component shows a text field with 'List box item 8 I' and a down-arrow button. Below it, the expanded list is shown with items 4 through 11, where 'List box item 8' is highlighted. +Dimension lines for 'XPos' and 'YPos' indicate the positioning of these elements within the main dialogue box frame. +Technical reference code at the bottom right: T0824400-95/d35. + +Diagram of a combination box within a dialogue box. The dialogue box has a title bar 'Dialogue box'. Inside, there are two list boxes. The left list box is titled 'List box item 10 I' and contains items 6 through 16. The right list box is titled 'List box item 8 I' and contains items 4 through 11. Both list boxes have a width and height dimensioned. The right list box has a drop-down arrow button next to it. A text label 'Drop down combination box before the drop down push button is validated' is positioned above the right list box. The diagram also shows XPos and YPos dimensions for the list boxes and the dialogue box. + +FIGURE 36/T.107 +Combination box + +###### List item attributes + +- **ListIndex:** This attribute carries the index of the next list item in the component description. It allows in a modify command the modification of a specific list item. The list indices shall be defined in an ascending order. The list indices may not be consecutive in order to allow easy updating of the list (inserting of list items). The terminal shall present a consecutive list to the user, sorted by the ascending value of the list indices corresponding to the list text. If in modify command a list index for a list item is used which is already existing, then the existing list item is replaced. If in a modify command a list index of a list item is used that is not existing in the terminal, the new list item shall be added. If in a modify command a list index is referenced which is already existing but in the modify command the corresponding attribute “ListText” is missing, then the referenced list item on the terminal shall be deleted. +- **ListText:** This attribute carries the text content of a list item. +- **BIN:** The BIN of the component. +- **ItemActAct:** This attribute carries the code for the local action which is associated to the item and triggered by its activation. +- **ItemActVal:** This attribute carries the code for the local action which is associated to the item and triggered by its validation. + +#### 7.6.1.13 The Slider component + +##### Description + +The slider offers the selection of an analogue value by moving an adjustable marker on a slide bar between a minimum and a maximum value. The intervals are set by the application. + +The Slider component consists of the following items: + +- a) Slider (with the movable marker, the initial marker position shall correspond to the default value, set by application); +- b) Text Label (naming the slider); +- c) MinLabel (the lowest selectable value), optional; +- d) MaxLabel (the highest selectable value), optional; +- e) DirectInputField (optional), an input and output field which contains: + - 1) the initial value when the Slider is activated; + - 2) the values in text form corresponding to the slider movements; + - 3) an Input field for user inputs of the slider position. + +The Slider Component may be oriented in vertical and horizontal direction. All items shall fit in the rectangle determined by the component dimensions. + +A local action which is triggered on the validation shall be performed when the user deactivates the component. + +##### Behaviour + +When the Slider Component is active the marker can be moved by striking the cursor keys or by mouse clicks. If the optional DirectInputField is present, the user is able to put in values directly by key strokes. The changed values shall be displayed immediately in the DirectInputField. The marker shall be moved onto a position which is relative to this value input. In the other case, when the marker is moved, the displayed value shall refer to this movement. The MinLabel and the MaxLabel (If they are present) are indicating the range, within a choice is available. + +##### Interactive functionality + +- local input functionality of the DirectInputField (application dependent); +- local positioning of the slider marker; +- validation by deactivation of the component; +- validation. + +##### Visual aspect (see Figure 37) + +![Diagram of the Slider component within a Dialogue box.](49fe8fe978c0f7e73112d231feb377eb_img.jpg) + +The diagram illustrates the visual structure of a slider component within a 'Dialogue box'. The box is defined by its 'XPos' and 'YPos' attributes. Inside, two sliders are shown. 'Slider 1' is the primary focus, with its 'Height' and 'Width' dimensions indicated. It consists of a 'Textlabel' (displaying '-4'), a 'DirectionputField' (a dashed box with left and right arrows), a 'MinLabel' ('-10'), a 'Slider' (a horizontal bar with a central marker), and a 'MaxLabel' ('10'). 'Slider 2' is shown below it, also with 'Height' and 'Width' dimensions. The diagram is identified by the code 'T0824410-95/d36'. + +Diagram of the Slider component within a Dialogue box. + +FIGURE 37/T.107 + +##### Slider component + +##### Attributes + +- CIN: This attribute carries the Component Identification Number. +- XPos: This attribute carries the horizontal position of the element in NDC. +- YPos: This attribute carries the vertical position of the element in NDC. +- Width: This attribute carries the width of the component. +- Height: This attribute carries the height of the component. +- Closed: The element shall be in the closed state. +- NotAccessible: The element shall not be accessible. +- Label: This attribute carries an alphanumeric text string. +- LabelFont: FIN of the label. + +- **MinValue:** The lowest adjustable value. +- **MaxValue:** The highest adjustable value. +- **Increment:** The interval size between two adjustable values. +- **InitialValue:** The initial value, when the Slider Component is opened. +- **Negative:** This attribute can be associated with MinValue, MaxValue, InitialValue and indicates that the values are negative. +- **DirectIn:** This attribute indicates that MinValue and MaxValue should be displayed and the user's direct input should be allowed. +- **Vertical:** The element shall be presented vertically. +- **LocActAct:** Specifies the code for the local action which is associated to the component and triggered by its activation. +- **LocActVal:** Specifies the code for the local action which is associated to the component and triggered by its validation. + +#### 7.6.1.14 The Sensitive Area component + +##### Description + +A Sensitive Area component is an area, non materialized, in which the application permits a validation operation. The Sensitive Area component is intended to be used associated with a Graphic Output Area component of the Dialogue Box. For the use with text components, the in-text attributes for the definition of sensitive text are more appropriate. The sensitive area is a rectangle inside the dialogue box. + +If the attribute locator is set, the terminal shall send upon validation not only its CIN to the VEMMI application, but also the coordinates of the cursor in NDC at the time of the validation with respect to the component origin. + +##### Behaviour + +When active a visible effect (e.g. thread, dot lines) can be implemented. + +##### Constraints + +A Sensitive Area shall not be covered by other components or items which are sensitive to user interaction, in order to avoid conflicts. + +##### Interactive functionalities + +- activation; +- validation. + +**Visual aspect** (see Figure 38) + +##### Attributes + +- **CIN:** Specifies the Component Identification Number. +- **XPos:** Specifies the horizontal position sensitive area. +- **YPos:** Specifies the vertical position of the sensitive area. +- **Width:** Specifies the width of the sensitive area. +- **Height:** Specifies the height of the sensitive area. +- **Closed:** The element shall be in the closed state. +- **NotAccessible:** The element shall not be accessible. + +- **Locator:** The position of the cursor in NDC at the time of the validation with respect to the component origin shall be sent with each report command. +- **LocActAct:** Specifies the local actions which are associated to the component and triggered by its activation. +- **LocActVal:** Specifies the local actions which are associated to the component and triggered by its validation. If the locator attribute is set, each report action shall also contain the coordinates of the cursor in NDC at the time of the validation with respect to the component origin. + +![A diagram of a 'Dialogue box' containing a sensitive area. The sensitive area is a dashed rectangle enclosing a grayscale image of a fish and the text 'JONAS & VINCENT'. Below the sensitive area, the text 'Bitmap with text in a sensitive area' is displayed. The entire content is within a thick black rectangular frame labeled 'Dialogue box' at the top.](47a2eefc809bb8f943219ae2149d1655_img.jpg) + +T0821430-95/d37 + +A diagram of a 'Dialogue box' containing a sensitive area. The sensitive area is a dashed rectangle enclosing a grayscale image of a fish and the text 'JONAS & VINCENT'. Below the sensitive area, the text 'Bitmap with text in a sensitive area' is displayed. The entire content is within a thick black rectangular frame labeled 'Dialogue box' at the top. + +FIGURE 38/T.107 +**Bitmap, text and sensitive area** + +## 7.7 The Message Box + +### Description + +The Message Box is a rectangular area in the DDA which contains text information. + +Four specified types of message are defined: + +- general message; +- information message; +- warning message; +- action message. + +This information can be used to add an icon characterizing the type of the message to the presentation of the message box. + +An attribute of the Message Box specifies if the terminal should perform a sound at the time the Message Box is opened. + +The Message Box can be provided with a border area which should be equal to one character position. When a border is requested, a frame shall be drawn by the terminal. This frame drawing is terminal dependent. + +### Behaviour + +An attribute of the Message Box specifies the lifetime of a Message Box. The following three values are available: + +- destroy by any user interaction; +- close by any user interaction; +- destroy by the user validation of an implicitly defined button; +- close by the user validation of an implicitly defined button; +- no implicit lifetime is defined. + +The destroying or closing of the Message Box shall not induce any report to the server. + +If no position is defined by the VEMMI application, the terminal shall centre the Message Box in the DDA. + +If no dimensions are defined by the VEMMI application, the terminal shall calculate the appropriate size of the Message Box in order to have enough room to display the text message and the possible Push Button. The label and the size of the possible Push Button are terminal dependent. + +### Interactive functionality + +- moving; +- validation. + +**Visual aspect** (see Figure 39) + +![Diagram of a Message box with a warning message.](061a752e081b43db4964482b0349f751_img.jpg) + +The diagram illustrates a 'Message box' window. At the top, a black header bar contains the text 'Message box'. Inside the box, a 'Warning icon' (a circle with an exclamation mark) is shown next to the word 'Warning'. To the right of this is the 'Text message' area. Below the warning icon, there is an 'OK' button, which is an implicitly defined push button. A line points from the label 'Implicitly defined push button' to the 'OK' button. + +Diagram of a Message box with a warning message. + +T0815790-94/d38 + +FIGURE 39/T.107 +Message box with a warning message + +### Attributes + +- XPos: Specifies the horizontal position of the message box. +- YPos: Specifies the vertical position of the message box. +- Width: Specifies the width of the message box. +- Height: Specifies the height of the message box. +- Closed: The element shall be in the closed state. +- MessageType: One of: general, information, warning, action. +- Modal: The element shall be modal. +- NoBorder: The element shall not have a border. +- AttributedText: Text of the message with in-text attributes. +- MaxTime: Time period in seconds. +- Lifetime: The events which lead to the destruction of the message box. +- NoSound: The terminal should not perform a sound when the message box is opened. + +## 7.8 Operative object + +With this object an application references a program which will be linked to the VEMMI application. This object type provides a method to extend the capabilities of an application during runtime. Via the service VEMMI\_Create\_Object the host application defines the operative object. The program is started with VEMMI\_Open\_Object. After termination the control is given back to the application. + +The program itself has been downloaded via file transfer, is part of the operating system or its presence has been negotiated in another way. It is referenced with its filename. It is up to the host to ensure that the called program is started faultless, by providing the correct program parameters. An often used method to extend the functions of programs during runtime is the use of Dynamic Link Libraries, DLLs. + +The program referenced with an operative object can be of the following types: + +- standalone program; +- program with a filter interface. + +For the purpose of operative objects, the services VEMMI\_Create\_Object VEMMI\_Open\_Object VEMMI\_Destroy\_Object are used. The program name and the program parameters are defined as attributes of the operative object. + +Two parameters, program description and the source identification, can be used by the terminal to evaluate information to be presented to the user or only to be recorded. This precaution is necessary in order to help the user to detect programs which have been linked to the VEMMI application with a sabotage intent. Their effect on the terminal may not be harmless. The terminal can answer the host “The user refused the start of the program!”. On which basis such an answer is generated is application dependent, but at least the information is available on a structured basis. If the terminal cannot find the program, the host has to be informed with a specific error message. + +### Requirements for standalone programs + +The program has no data exchange channel with the VEMMI local manager during the execution. Program parameters can be defined by the host application and supplied to the program when started. The operative object has no visual effect on the terminal and cannot be activated directly by the user, but the started program may use the local UI on an application specific basis. See Figure 40. + +![Diagram of Standalone programs architecture showing the flow from Operative object to VEMMI local manager and dispatcher, and then to Communication.](401f020d9ab5904f584424eabb596d2c_img.jpg) + +``` + +graph TD + A[Operative object +(standalone program)] -- "Start and stop +of operative object" --> B[VEMMI local manager +VEMMI command +dispatcher] + B --> C[Communication] + +``` + +T0821470-95/d39 + +Diagram of Standalone programs architecture showing the flow from Operative object to VEMMI local manager and dispatcher, and then to Communication. + +FIGURE 40/T.107 +**Standalone programs** + +The VEMMI command dispatcher is responsible for delivering the VEMMI commands between the VEMMI local manager and the communication part. All these interfaces are terminal and implementation dependent. They are used in this description to explain the integration of the two types of operative objects in the VEMMI terminal architecture. + +### Requirements for programs with filter interface + +The program with filter interface has the possibility to access the VEMMI command dispatcher. The command dispatcher forwards the commands to the operative object, which decides to process them or forward them to the VEMMI local manager. This mechanism works also for the sending direction. The operative object has no visual effect on the terminal and cannot be activated directly by the user, but the started program may use the local UI on an application specific basis or through the VEMMI local manager. All these interfaces of such a program are terminal and implementation dependent and are not further described in this Recommendation. If an operative object receives a `VEMMI_Close_Object` with its own OIN from the host or it is terminated by the VEMMI local manager, it shall stop and the VEMMI local manager shall continue. All data exchange channels to the VEMMI local manager are disabled. See Figure 41. + +### Attributes + +- Closed: The element shall be in the closed state. +- ProgName: The name of the program. +- ProgFilename: Filename of the program. +- ProgDescr: Description of the program. +- ProgAbout: Source identification of the program. +- ProgPar: List of parameters for the start of the program (optional). +- ProgType: Program type, standalone or with filter interface. + +![A vertical flow diagram showing the interaction between four components: VEMMI local manager, Operative object (program with filter interface), VEMMI command dispatcher, and Communication. The components are connected by bidirectional arrows. The arrow between VEMMI local manager and Operative object is labeled 'VEMMI command exchange'. The arrow between Operative object and VEMMI command dispatcher is labeled 'Start and stop of operative object'. The reference 'T0821480-95/d40' is located at the bottom right of the diagram.](9c80cf99954eb0142f694456d39fae4b_img.jpg) + +``` + +graph TD + A[VEMMI local manager] <-->|VEMMI command exchange| B[Operative object +(program with filter interface)] + B <-->|Start and stop of operative object| C[VEMMI command dispatcher] + C <--> D[Communication] + +``` + +T0821480-95/d40 + +A vertical flow diagram showing the interaction between four components: VEMMI local manager, Operative object (program with filter interface), VEMMI command dispatcher, and Communication. The components are connected by bidirectional arrows. The arrow between VEMMI local manager and Operative object is labeled 'VEMMI command exchange'. The arrow between Operative object and VEMMI command dispatcher is labeled 'Start and stop of operative object'. The reference 'T0821480-95/d40' is located at the bottom right of the diagram. + +FIGURE 41/T.107 +**Programs with filter interfaces** + +## 7.9 Bitmap resource object + +### Description + +A bitmap object contains either the bitmap definition itself or only a reference to a file with the bitmap definition. + +### Direct Bitmap Definition + +The pixel matrix contains indices into the colour table or the RGB-components for each pixel. The attribute list is composed of two parts: the first is common to the two cases and the second is dependent from the colour definition. The first part is as follows: + +- BmWidth: Width of the bitmap in pixel. +- BmHeight: Height of the bitmap in pixel. +- BmCompr: Compression type for the colour list. This value is currently not defined and only uncompressed colour lists can be specified (optional). + +In the case of a colour index definition, the second part of the attribute list is as follows: + +- BmBitsPerPixel: Number of bits per pixel. The value must be 1, 4 or 8 (optional, default value: 1). +- BmClrEntry: The colour table index on which all other colour indices from the index list are based (optional, default value: 0). + +- **BmClrIxList:** List of colour indices. This list contains $BmWidth * BmHeight$ colour indices. Depending on the number of bits per pixel, each colour index is in the range $0 .. 2^{BmBitsPerPixel}-1$ . The colour indices are ordered row-by-row from left to right. The start point is the lower left corner of the bitmap. A colour index 0 means a colour table index equal to **BmClrEntry**. All other indices are relative to **BmClrEntry**. + +In the case of a colour component definition, the second part of the parameter list is as follows: + +- **BmBitsPerComp:** Number of bits per colour component. The value must be in the range 1 to 8 (optional, default value: 8). +- **BmClrCompList:** List of RGB triplets. This list contains $BmWidth * BmHeight$ triplets. The RGB-triplets are ordered row-by-row from left to right. The start point is the lower left corner of the bitmap. + +### File Bitmap Definition + +Such a bitmap is defined from a picture file stored in the terminal. The file has been transmitted with a resource transfer service or by other means. A parameter indicates the file coding. If the file could not be converted in a suitable bitmap (upon **VEMMI\_Create\_Object**) the terminal shall send an error message to the host. + +- **Filename:** Name of the file with the bitmap definition. +- **PictFileType:** Type of the picture file (one of JPEG, GIF, BMP). + +The picture files conform to one of the following specifications: + +- **JPEG:** Baseline system from ISO/IEC IS 10918 | Rec. ITU-T.81 “Digital compression and coding of continuous-tone still images” +- **GIF:** Graphics Interchange Format (sm) Version 89a. Compuserve Incorporated Columbus, Ohio, USA. Although the Version 89a is referenced a terminal has to support only the functions contained in the Version 87. +- **BMP:** Microsoft Windows Device-Independent Bitmap (DIB) with RLE4, RLE8 and 1, 4, 8 or 24 bits per pixel. + +## 7.10 Videotex resource object + +### Description + +A Videotex object contains either the Videotex content itself or only a reference to a file with the Videotex content. + +### Attributes + +- **VTX:** VTX content. +- **Filename:** Name of the file with the VTX content. + +## 7.11 Text resource object + +### Description + +This object defines text content as a resource which can be referenced via the “Text Identification Number” (TIN). It contains either the text content itself or a reference to a file with the text content. In both cases the text content can contain in-text attributes, with references to font resource objects. + +### Attributes – Direct text resource definition + +- **Text:** Text. +- **FIN:** Reference to a font resource object. + +### Attributes – File text resource definition + +- Filename: Name of the file with the text content. +- TextFileType: One of: + - text; + - references to a font resource objects and text. + +## 7.12 Font resource object + +This object combines a set of text attributes in on font resource which can be referenced via the FIN. + +### Attributes + +- FnFamily: The font family: SWISS, ROMAN or FIXFONT. (optional, default value: SWISS). +- FnHeight: Character height. (optional, default value: 10). +- FnBold: Character weight bold (optional). +- FnUnderline: Underlined (optional). +- FnItalic: Italic (optional). +- FnColour: Font colour: colour index. (optional, default: black). + +## 7.13 Metacode object + +The metacode object contains VEMMI commands. This object provides an easy way to avoid unnecessary dialogue steps with the host application. The command VEMMI\_Open\_Object starts the processing of the metacode object and after termination it is automatically in the closed state. The commands (the content of the metacode object) are processed in the same way as if they were received from the host application. For the content of the metacode object the following restrictions apply: + +- the creation of a metacode object is not allowed; +- only host commands are allowed; +- a VEMMI\_Open\_Object command of another metacode object is not allowed (a VEMMI\_Open\_Blocking\_Object is allowed). + +### Attributes + +- VEMMICommands: VEMMI commands + +## 7.14 VEMMI bitmap data type definition + +See 7.9. + +## 7.15 The VEMMI content encoding identification catalogue + +Table 38 provides an overview of content encoding identifications defined in the VEMMI catalogue: + +TABLE 38/T.107 + +### **VEMMI content encoding identification catalogue** + +| | | +|-----------------------------------|-------------------------------------------------------------------------------------------------------| +| For text data encoding: | | +| | T.51 String as defined in Annex A | +| | Recommendation T.52 [3] | +| | VEMMI high quality text | +| | ISO 8859-Series [13]. (Fully-formed accented char.) | +| | ISO 10646-1 [15] [multi-octet character set (Unicode)] | +| | Shift JIS Code (for Japanese characters) | +| For still picture data encoding: | | +| | Annex F/T.101 [4] (Photovideotext) | +| | ISO 10918-1 [16] (JPEG) | +| | VEMMI device independent bitmap | +| | Graphics Interchange Format (sm) Version 98a.
Compuserve Incorporated Columbus, Ohio, USA | +| | Microsoft Windows Device-Independent Bitmap (DIB)
with RLE4, RLE8 and 1, 4, 8 or 24 bits per pixel | +| For graphic data encoding: | | +| | Annex B/T.101 and Annex C/T.101 [4] (Videotex) | +| | ISO 8632 [12] (CGM) | +| For audio data encoding: | | +| | Annex E/T.101 [4] | +| | WAVE format | +| | MIDI format | +| For moving picture data encoding: | | +| | ISO 11172-2 [18] (MPEG Video) | +| | Recommendation H.261 [7] (videophone) | +| For audiovisual data encoding: | | +| | ISO 11172-1 [17] (MPEG System) | +| | Recommendation H.320 [8] (videophone) | + +# 8 Complete coded representation of the VEMMI + +## 8.1 Introduction + +This clause contains the syntax notation, the VEMMI header and the syntax of the commands, objects, components and local actions. + +## 8.2 Notation used + +The notation a/b with a, b = 0..15 denotes a byte value in hexadecimal. + +The bits in a byte are noted b8, b7, ..., b1. The bit b8 is the high-order or most significant bit. + +The syntax of the commands, objects, components and local actions is defined with a formal grammar using the following notation: + +| | | +|--------------------------|----------------------------------------------| +| | – nonterminal; | +| | – terminal; | +| | – terminal, hexadecimal value: a, b = 0..15; | +| * | – 0 or more occurrences; | +| + | – 1 or more occurrences; | +| o | – optional (0 or 1 occurrences); | +| := | – symbol-1 has the syntax of symbol-2; | +| | – symbol-1 or alternatively symbol-2; | +| | – symbol with the stated value; | +| { comment } | – explanation of a symbol or production. | + +## 8.3 Overall switching of coding environment + +ISO/IEC 9281 [14] describes a technique for identifying coding methods. The videotex VEMMI mode is one of the coding methods identified by ISO/IEC 9281 [14]. The diagram in Figure 42 gives an overview of the relationship between the videotex data syntaxes and ISO/IEC 9281 [14] coding environments. + +From an ISO 2022 [10] environment, a videotex data syntax can be explicitly entered using an ESC 2/5 F code. This is also the mechanism used for entering from an ISO 2022 [10] environment into an ISO/IEC 9281 [14] environment. The F code (“final byte”) is allocated and registered, according to ISO 2022 [10] by the registration authority ISO 2375 [11]. According to Appendix B/ISO 2375 [11], the videotex data syntaxes are regarded as “coding systems different to that of ISO 2022 [10]”. The F codes are 4/3 for CCITT data syntax I, 4/4 for CCITT data syntax II and 4/1 for CCITT data syntax III. + +Since a videotex terminal usually begins operation, by default, in one of the data syntaxes, it shall not be mandatory to first send an ESC 2/5 F code (F is 4/1, 4/3 or 4/4). The diagram shows how these codes can be used to switch a videotex terminal supporting more than one data syntax from one data syntax to another. + +### 8.3.1 Switching into the VEMMI mode + +A videotex terminal operating within one of the data syntaxes (i.e. a coding system other than that described by ISO 2022 [10]) can enter the ISO/IEC 9281 [14] environment of the VEMMI mode according to their own rules. In the case of videotex for switching into the ISO/IEC 9281 [14] environment of the VEMMI mode, the Picture Code Delimiter (PCD) of the first Picture Element (PE) is used. The Coding Method Identifier (CMI) is used to distinguish between picture coding methods. In the case of videotex this shall be, for example, a distinction between audio, Photographic and VEMMI data. + +NOTE – As ISO/IEC 9281 [14] was developed especially for the identification of picture coding in ISO 2022 [10] environments, the word “picture” is often used in the definitions, even when applicable to “audio”, for example. ISO has already accepted to make use of ISO/IEC 9281 [14] for non-pictorial information. + +![Diagram of the Global switching mechanism showing three data syntaxes (I, II, III) and a coding method, all within an ISO 2022 Environment.](b3335932702b8668e62791e9fd12c9ff_img.jpg) + +The diagram illustrates the global switching mechanism within an ISO 2022 Environment, Default = ISO 646. It shows three data syntaxes (I, II, III) and a coding method, all connected to a central output line. + +- Data Syntax I:** + - Input: ESC 2/5 4/0 + - Rank: ESC 2/5 4/3 + - Options: + - (DI) Alpha photo + - ESC 7/0 CMIp Photographic + - ESC 7/0 CMIa Audio + - ESC 7/0 CMIv VEMMI +- Data Syntax II:** + - Input: ESC 2/5 4/4 + - Profile (P1-4): + - US 2/0 ... 3/15 Other + - US 3/4 US 3/5 Old photo + - US 4/0 ... 7/15 AM display + - ESC 7/0 CMIp Photographic + - ESC 7/0 CMIa Audio + - ESC 7/0 CMIv VEMMI + - T.50 based text +- Data Syntax III:** + - Input: ESC 2/5 4/1 + - Options: + - Other Alpha geo + - ESC 7/0 CMIp Photographic + - ESC 7/0 CMIa Audio + - ESC 7/0 CMIv VEMMI +- Coding Method:** + - Input: ESC 2/5 F + - Any ISO/IEC 9281 registered coding method + +Arrows indicate the flow of data from the inputs to the respective syntaxes and then to the output line. A feedback arrow is shown at the top of the ISO 2022 Environment box. + +Diagram of the Global switching mechanism showing three data syntaxes (I, II, III) and a coding method, all within an ISO 2022 Environment. + +T0815800-94/d41 + +DI is data syntax I specific + P is a profile in data syntax II + F is a final code assigned by the ISO 2022 [10] registration authority + CMIa is any CMI for videotex audio data + CMIp is any CMI for videotex photographic data + CMIv is any CMI for VEMMI data + Rank is data syntax I specific + +FIGURE 42/T.107 + Global switching mechanism + +### 8.3.2 ISO/IEC 9281 [14] syntax structure + +The high-level format of the syntax is as defined in ISO/IEC 9281 [14]. + +In the following description of the syntax 8-bit coding is assumed, thus the word “byte” is used with bit 8 set to zero. The coding described in ISO 9281 [14] is also valid in a 7-bit environment. In this case, the word “byte” shall be interpreted as meaning “7-bit byte” and the most significant bit, bit 8, shall not be used. + +The structure of the coding is as follows: + +``` +PE ::= PCE PDE; +PCE ::= PCD CMI LI; +PCD ::= 01/11 07/00; +CMI ::= PM PI; +PM ::= 02/05 (videotex VEMMI mode); +PI ::= 04/00; +LI1) ::= x111 1111...; + ::= x10D DDDD (k = n); + | x11D DDDD (1 = Data
Entity | +| | CMI | Method | | | +| | | Identifier | | | +| Picture | | | Length | | +| Coding | | | Indicator | | +| Delimiter | | | | | +| | PM | PI | | | +| | Picture | Picture | | | +| | Mode | Identifier | | | + +FIGURE 43/T.107 +Structure of a Picture Entity + +1) 5.2.7/ISO 9281 [14], should be consulted for the description of the Length Indicator. + +NOTE 1 – In videotex VEMMI mode the size of a file containing an encoded VEMMI object can be rather large. One object may be transmitted in several PEs. The use of several PEs could facilitate the termination of the transmission of an object by the user. + +The Picture Control Entity (PCE) consists of a Picture Coding Delimiter (PCD) and a Coding Method Identifier (CMI) followed by a Length Indicator (LI). + +The Picture Coding Delimiter (PCD) is a fixed sequence of two octets: 01/11 07/00. + +NOTE 2 – 01/11 is ESC. + +The Coding Method Identifier (CMI) consists of a Picture Mode (PM) octet, followed by a Picture Identifier octet (PI). For VEMMI the PM is 02/05 as registered by ISO 9281 [14]. The PI octet has the value 04/00. + +The length indicator (LI) specifies the number of bytes in the Picture Data Entity. Its encoding is described in the following (excerpt from ISO/IEC 9281 [14]): + +| b 8 | b 7 | b 6 | b 5 | b 4 | b 3 | b 2 | b 1 | +|----------------|----------------|----------------|----------------|----------------|----------------|----------------|----------------| +| X | ONE | ZERO
or ONE | | | | | | + +Bit b8 of each byte shall be ignored. Bit b7 of each byte shall be set to ONE. Bit b6 of each byte shall be the Extension Flag. The LI value is specified in binary notation as an unsigned number using bits b5 to b1 with the weights 24, 23, 22, 21 and 20, respectively. If the value of LI is less than, or equal to, 31 it shall be represented by one byte and the Extension Flag shall be set to ZERO. If the value of LI is larger than 31 it shall be represented by more than one byte. The most significant part of this value shall be recorded in the first byte. The Extension Flag shall be set to ONE in all bytes except the last where it shall be set to ZERO. + +Values of LI: + +- 1 byte: X111 1111 +- 2 bytes: $0 \leq \text{LI} \leq 2^5 - 1$ +- 3 bytes: $2^5 \leq \text{LI} \leq 2^{10} - 1$ +- . . . . . . . +- n bytes: $2^{5(n-1)} \leq \text{LI} \leq 2^{5n} - 1$ + +Examples: + +LI = 31 + +| | | | | | | | | +|---|---|---|---|---|---|---|---| +| X | 1 | 0 | 1 | 1 | 1 | 1 | 1 | +|---|---|---|---|---|---|---|---| + +LI = 33 + +| | | | | | | | | +|---|---|---|---|---|---|---|---| +| X | 1 | 1 | 0 | 0 | 0 | 0 | 1 | +|---|---|---|---|---|---|---|---| + +First byte + +| | | | | | | | | +|---|---|---|---|---|---|---|---| +| X | 1 | 0 | 0 | 0 | 0 | 0 | 1 | +|---|---|---|---|---|---|---|---| + +Second byte + +## 8.4 VEMMI Command Syntax + +| Host command | Command syntax | +|------------------------------------------|-----------------------------------------------------| +| VEMMI_Set_Translation_Mode | | +| VEMMI_Open | | +| VEMMI_Close | | +| VEMMI_Resume | | +| VEMMI_Suspend | | +| VEMMI_Close_All | | +| VEMMI_Identify_Term_Cap | | +| VEMMI_Set_Options | o | +| VEMMI_Reset_Col_Table | | +| VEMMI_User_Lock | | +| VEMMI_User_Unlock | | +| VEMMI_Open_Object | | +| VEMMI_Close_Object | | +| VEMMI_Destroy_Object | | +| VEMMI_Obj_Access_Disable | | +| VEMMI_Obj_Access_Enable | | +| VEMMI_Create_Object | | +| VEMMI_Delete_Outdated_Objects | + | +| VEMMI_Modify_Component
(see also 9.6) | | +| VEMMI_Obj_Location_Change | | +| VEMMI_Load_Col_Table | | +| VEMMI_Open_Application | | +| VEMMI_Store_Objects | | +| VEMMI_Erase_Objects | | +| VEMMI_Open_Blocking_Object | | +| VEMMI_Resource_Transfer | | +| VEMMI_Store_Objects_Response | | +| VEMMI_Object_Retransmission | | +| VEMMI_Identify_Term_Cap_Resp | + | +| VEMMI_Open_Application_Response | | +| VEMMI_User_Data | | +| VEMMI_Error | | +| VEMMI_Resource_Transfer_Abort | | + +| | | +|------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| +| := | <2/0> { no translation }
<2/1> { 3 in 4 encoding }
<2/2>     { 7 shift encoding } | +| := | | +| := |         { Version } | +| := | | +| := |     { VEMMI as described in this Recommendation } | +| := | o | +| := | | +| := |         { in seconds } | +| := | o o o opc>o | +| := | | +| := | o o o o | +| := | | +| := |