B6ZS

B6ZS: Abbreviation for bipolar with six-zero substitution . A T-carrier line code in which bipolar violations are deliberately inserted if user data contain a string of 6 or more consecutive zeros.

Note 1: B6ZS 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: B6ZS is used in the North American hierarchy at the T2 rate.

Source: from Federal Standard 1037C