ITU-T Rec. H.242 (03/1996) – System for establishing communication
between audiovisual terminals using digital
...
Summary
Source
FOREWORD
CONTENTS
1 Scope
2 Normative references
3 Definitions and conventions
4 Abbreviations
5 Terminal capabilities
5.1 Audio capabilities
5.2 Video capabilities
5.3 Transfer rate capabilities
5.4 Data capabilities
5.5 Terminals on restricted networks: capability
5.6 Encryption and extension-BAS capabilities
5.7 Null capability
6 Transmission
6.1 Transmission modes
6.2 Establishment of compatible modes of operation
7 Frame structure
8 Basic sequences for in-channel procedures
8.1 Capability exchange sequence A
8.1.1 Sequence A at the start of a call
8.1.2 Sequence A during a call
8.1.3 Identification of the end of sequence A
8.2 Mode switching sequence B
8.3 Frame reinstatement sequence C
9 Mode initialization, dynamic mode switching and Mode 0 forcing
9.1 Mode initialization procedure
9.1.1 Single channel
9.1.2 Additional channels
9.2 Dynamic mode switching (see Figure 2)
9.2.1 Dynamic mode switching from a framed mode to another framed mode
9.2.2 Dynamic mode switching from a framed mode to an unframed mode
9.2.3 Dynamic mode switching from an unframed mode to another mode (framed or unframed)
9.2.4 Dynamic mode switching involving change of active additional channels
9.3 Mode 0 forcing procedure
9.3.1 Single channel operation
9.3.2 Two or more channels
9.4 Mode mismatch recovery procedure
9.5 Procedure for influencing the Mode transmitted from remote endpoint
10 Recovery from fault conditions
10.1 Unexpected loss of synchronization or frame alignment
10.1.1 Loss of frame alignment in the initial channel
10.1.2 Loss of frame alignment or synchronization in an additional channel
10.2 Recovery from loss of connection(s)
10.2.1 Renumbering of channels
10.2.2 Loss of an additional connection
10.2.3 Loss of the initial connection
11 Network consideration: call connection, disconnection and call transfer
11.1 Call connection
11.1.1 Initial channel
11.1.2 Additional channels
11.2 Terminal disconnection
11.3 Call transfer
11.4 Conferencing
12 Procedure for activation and de-activation of data channels
12.1 General
12.2 Procedures applicable to all data types
12.3 Equipment capable of operating using protocol according to Recommendation T.120
12.4 Data equipment not conforming to Recommendation T.120
12.5 Dummy Data
13 Procedures for operation in restricted networks
13.1 Network aspects
13.2 Terminal-network configurations and properties
13.2.1 Terminals connected to restricted networks providing 56 kbit/s bearers
13.2.2 Terminals connected to unrestricted networks providing 64 kbit/s bearers
13.2.3 Terminals connected to restricted networks providing higher rate bearers
13.2.4 Terminals connected to unrestricted networks providing higher rate bearers
13.2.5 56 kbit/s interconnecting a 64 kbit/s network
13.3 Transmission formats
13.3.1 Framing signal (56 kbit/s)
13.3.2 Transmission formats (56 kbit/s operation)
13.3.3 n × 56 kbit/s operation
13.3.4 n × H0 operation
13.3.5 Dynamic allocation within a primary-rate connection
13.4 Procedures
13.4.1 Capability values to be transmitted
13.4.2 Selection of appropriate restricted Mode
13.4.3 Restricted Mode transmitted
13.4.4 Restricted Mode received
13.4.5 Restricted "bottleneck" between two unrestricted networks
13.4.6 Interworking between Restrict_L and Restrict_P endpoints
14 Procedure for use of BAS-extension codes
15 Bit occupancy and the sequencing of BAS codes
16 Procedure for dealing with single/multiple channel interconnection
17 Procedure for use of encryption control signal channel
18 Transmission of network addresses
18.1 Address of initial connection
18.1.1 Calling endpoint
18.1.2 Called endpoint
18.2 Addresses of additional connections
18.2.1 Calling endpoint
18.2.2 Called endpoint
Appendix I – Initialization: Case of videophone to Recommendation H.320, type Xb2/3
Appendix II – Mode-0 forcing: Case of videophone to Recommendation H.320, type Xb2/3
Appendix III – Example of use of message structure
Appendix IV – Examples of symmetrical and asymmetrical transmission modes
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
Appendix VI – Hierarchical capability BAS codes
Appendix VII – Interpretation of received audio capability BAS codes
Appendix VIII – Examples of legal and illegal capability BAS sequences
Appendix IX – BAS control and indication codes
Appendix X – An algorithm to determine whether an incoming bit stream was encoded by µ-law or A-law PCM
X.1 Basic determination algorithm
Appendix XI – Mode preference indication codes