ITU-T H.140-1989 Multipoint International Videoconference System - Line Transmission of Non-Telephone Signals - Transmission of Sound-Programme and Television Signals Study Group XV; 8 pp
MCUs not equipped to mix Recommendation G.722 audio will set bit 3.1.1 to zero.
ITU-T H.140-1989 history
1989ITU-T H.140-1989 Multipoint International Videoconference System - Line Transmission of Non-Telephone Signals - Transmission of Sound-Programme and Television Signals Study Group XV; 8 pp