Abbreviation for bipolar with eight-zero substitution T-carrier line code used on clear-channel T1 data lines along with the Extended Super Frame framing method (most common occurance). This line code allows for 64Kbps per channel. In B8ZS, bipolar violations are inserted if user data contains a string of 8 or more consecutive zeros to maintain synchronization when the binary data stream doesn't have enough 1's (at least 12.5%) and doesn't meet the requirements of no more than 15 consecutive zeros for framed signals and no more than 14 consecutive zeros for unframed signals. B8ZS is an alternate of AMI line code. Each end of a B8ZS coded circuit require B8ZS compatible CSU's.

Most often, B8ZS is seen in use on point-to-point clear-channel T-1 data communications lines. An example of the equipment that can be used to terminate each end of such a data line is the Adtran TSU LT.