The system described in this Recommendation makes possible the transmission of sound signals, coded by new methods recommended by ITU-R Study Group 10 and standardized by ISO/IEC 11172-3, on 1 to 6 B-channels of the N-ISDN or on permanent connections with a 2048 kbit/s (or 1544 kbit/s) frame. In the case of transmission via the N-ISDN, Recommendation H.221 is used to aggregrate up to six B-channels while maintaining the bit sequence integrity. The revised text contains clarifications that reflect experience gained in implementing the current version of this Recommendation, and a new chapter on transmission of program-associated data in the ancillary data field of the ISO frame.