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

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.

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