Bchannel

B-channel, in telecommunications, refers to a bearer channel in ISDN designed to carry user data. In the ISDN Basic Rate Interface (BRI), two B channels are available alongside a signaling D channel. Each B channel operates at 64 kbit/s, so the two B channels provide up to 128 kbit/s of user data, while the 16 kbit/s D channel handles call setup, signaling, and maintenance.

In ISDN, the Primary Rate Interface (PRI) uses many B channels in a single connection. In North America and Japan (T1), PRI typically consists of 23 B channels plus one 64 kbit/s D channel. In Europe (E1), PRI typically consists of 30 B channels plus one 64 kbit/s D channel. The B channels remain 64 kbit/s each and serve as the bearer paths for voice, data, or other services; the D channel carries signaling information for all the associated B channels.

B-channels are frequently multiplexed or bonded to achieve higher overall data rates when needed, beyond the capacity of a single 64 kbit/s channel. They are often used for traditional voice services, video conferencing, data transmission, and other applications that require consistent, dedicated bandwidth.

The term B-channel contrasts with the D-channel, which is dedicated to signaling and control rather than user data. The concept of B-channels and D-channels is central to ISDN’s method of separating bearer traffic from signaling, enabling multiple digital paths over a single ISDN line.

See also: ISDN, D-channel, DS0, BRIs, PRIs.