: 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