ITU-T Rec. H.242 (1990) – SYSTEM FOR ESTABLISHING
COMMUNICATION BETWEEN AUDIOVISUAL
TERMINALS USING DIGITAL CHANNELS ...
FOREWORD
1 Introduction
2 Terminal capabilities
2.1 Audio capabilities
2.2 Video capabilities
2.3 Transfer rate capabilities
2.4 Data capabilities
2.5 Terminals on restricted networks: capability
2.6 Encryption and extension-BAS capabilities
3 Transmission
3.1 Transmission modes
3.2 Establishment of compatible modes of operation
4 Frame structure
5 Basic sequences for in-channel procedures
5.1 Capability exchange sequence A
5.2 Mode switching sequence B
5.3 Frame reinstatement sequence C (see Figure 1/H.242)
6 Mode initialization, dynamic mode switching and mode 0 forcing
6.1 Mode initialization procedure
6.2 Dynamic mode switching (see Figure 3/H.242)
6.3 Mode 0 forcing procedure (see Figure 4/H.242)
6.4 Mode mismatch recovery procedure
7 Recovery from fault conditions
7.1 Unexpected loss of synchronization or frame alignment
7.2 Recovery from loss of connection(s)
8 Network consideration: call connection, disconnection and call transfer
8.1 Call connection
8.2 Terminal disconnection
8.3 Call transfer
8.4 Conferencing
8.5 PCM format conversion
9 Procedure for activation and de-activation of data channels
9.1 Data equipment not conforming to Recommendation H.200/AV.270
9.2 Equipment operating with an MLP according to Recommendation H.200/AV.270
9.3 Simultaneous transmission of low-speed data and MLP
10 Procedures for operation of terminals in restricted networks
10.1 Network aspects
10.2 Reference connections
10.3 Transmission formats
10.4 Interworking between 56 kbit/s and 64 kbit/s terminals
10.5 Interworking between H0 or H11 terminals in restricted and unrestricted networks
11 Procedure for use of BAS-extension codes
12 Bit occupancy and the sequencing of BAS codes
13 Procedure for dealing with 6B-H0 interconnection
14 Procedure for use of encryption control signal channel
APPENDIX I – Initialization: Case of Videophone to Recommendation H.320, Type Xb3
APPENDIX II – Mode-0 forcing: Case of Videophone to Recommendation H.320, Type Xb3
APPENDIX III – Example of use of message structure
III.1 Initial capability exchange, including MBE-cap
III.2 Subsequent capability exchange, including MBE capability message
III.3 Mode switch to non-standard mode using MBE command
APPENDIX IV – Examples of symmetrical and unsymmetrical transmission modes
IV.1 Example of symmetrical transmission mode
IV.2 Example of unsymmetrical transmission mode
APPENDIX V – Examples relating to data transmissions
V.1 Transfer-rate 1B, audio at 48 kbit/s, no video or video off
V.2 Transfer-rate 1B, audio at 16 kbit/s, no video or video off
V.3 Transfer-rate 1B, audio at 16 kbit/s, video on
V.4 Transfer-rate 2B, audio at 48 kbit/s, video on
V.5 Transfer-rate 2B, audio at 16 kbit/s, video on