B Channel

Also called the bearer channel, is a 64 Kbps circuit switched, duplexed channel that carries voice and/or data a part of ISDN PRI and ISDN BRI. (See ISDN).

B8ZS

Binary eight-zero substitution, also called Bipolar with eight-zero substitution, was originally developed by AT&T as a line encoding option for all 24 DS-0 channels on a T-1 network (DS-1).

A 1 is sent on a T-1 by sending a pulse, a zero ( 0 ) by not sending a pulse. The alternating mark rule demands that if the last pulse sent was of positive polarity, the next pulse sent must be negative. A T-1 device receiving two pulses in sequence of the same polarity experiences a bipolar violation (BPV).

The T-1 1s density rule specifies that the average number of 1s in the data should be at least 12.5% (one bit in eight) and there should be no more than 15 consecutive 0s in a T-1 data stream, lest the lack of 1s will destroy the synchronization between a sender and receiver.

B8ZS is used to prevent the loss of synchronization when long strings of zeros are transmitted. In B8ZS a specific sequence of valid pulses and intentional bipolar violations to the AMI line encoding method are used to represent a string of eight zeroes. Specifically, for any sequence of eight zeroes the following sequence is substituted: Three zeroes, a deliberate bipolar violation, a one, a zero, another deliberate bipolar violation, and another one. This pattern is recognized by configured equipment...