In the Integrated Services Digital Network (ISDN), the B-channel (Bearer Channel) is the channel that carries the voice or data for a call/session.
In ISDN, there are two levels of service: the Basic Rate Interface, intended for the home and small enterprise, and the Primary Rate Interface, for larger users. Both rates include a number of B- (bearer) channels and a D-channel. The B-channels carry data, voice, and other services. The D-channel carries control and signaling information.