: Abbreviation for bipolar with eight-zero substitution
. A T-carrier line code
in which bipolar violations are deliberately inserted if user data
contains a string
of 8 or more consecutive zeros.
Note 1: B8ZS 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: B8ZS is used in the North American hierarchy at the T1 rate. When European E1 was developed much later than T1, it was then common knowledge that forcing 'ones' into a DS0 would corrupt data. E1 uses another method called High Density Bipolar Three (HDB3) code.
Source: from Federal Standard 1037C