ITU-T Rec. H.320 NARROW-BAND VISUAL TELEPHONE SYSTEMS AND TERMINAL EQUIPMENT
FOREWORD
1 Scope
2 Definitions
3 System description
    3.1 Block diagram and identification of elements
    3.2 Signals
    3.3 Bit rate options and infrastructure
        3.3.1 Communication modes of visual telephone
        3.3.2 Terminal types of visual telephone
        3.3.3 Video codec
        3.3.4 Audio codec
        3.3.5 Frame structure
        3.3.6 Control and indication (C&I)
        3.3.7 Communication procedure
    3.4 Call control arrangements
        3.4.1 Establishment of a visual telephone call - Normal procedure
        3.4.2 Exceptional procedures for phases A and B
        3.4.3 Exceptional procedures during phase C
        3.4.4 Addition and dropping of channels during a visual telephone call
        3.4.5 Transmission and display of pictures at the start of a visual telephone call
    3.5 Optional enhancements
        3.5.1 Data ports
        3.5.2 Encryption
4 Terminal requirements
    4.1 Environments
    4.2 Audio and video arrangements
    4.3 Delay compensation in the audio path
    4.4 Control and indications (C&I)
5 Intercommunications
    5.1 Intercommunication between different visual telephone terminal types
    5.2 Intercommunication with telephony
        5.2.1 Intercommunication with ISDN telephones
        5.2.2 Intercommunication with PSTN telephones
    5.3 Intercommunication with other audiovisual terminals
6 Maintenance
7 Human factor aspects
    7.1 Physical section
    7.2 Logical section