B3ZS

B3ZS: Abbreviation for bipolar with three-zero substitution . A T-carrier line code in which bipolar violations are deliberately inserted if user data contain a string of 3 or more consecutive zeros.

Note 1: 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.

Note 2: B3ZS is used in the North American hierarchy at the T3 rate.

Source: from Federal Standard 1037C