ITU-T I.231.2 PDF

General description

This circuit-mode bearer service category allows:

- two users (e.g. terminals, PABXs) in a point-to-point configuration to communicate via the ISDN using speech encoding into 64 kbit/s digital signals over the B-channel, in both directions continuously and simultaneously for the duration of a call;

- three or more users in a multipoint configuration (refer to Recommendation I.254 for the supplementary service description for Three-Party Service and Conference Calling).

Tones and/or announcements to indicate the progress or otherwise of a call, are provided by the network.