B3ZS

B3ZS is an abbreviation for bipolar with three-zero substitution, a T-carrier line code in which bipolar violations are deliberately inserted if the stream of user data contains a string of 3 or more consecutive zeros.

B3ZS is used to ensure a sufficient number of transitions to maintain system synchronization when the user data stream contains an insufficient number of "ones" to do so.

B3ZS is generally used on T3 lines as per North American hierarchy.