The T-SERV II T1 Basic Channel Service Unit (CSU) meets all FCC and carrier requirements for a standard interface between the user and the network. Its transparent operation passes AMI/B8ZS and ESF/D4 enhanced T1 formats unaltered. All basic CSU functions are contained in the T-SERV II CSU, including bipolar violation (BPV) correction, Line Build-Out (LBO), loop-code generator, status indicators, test jacks, power options (line or local) and automatic keep-alive signal generation. Pulse Density enforcement can be set for 15 (AT&T TR62411), 47, or 80 (FCC Part 68) consecutive zeros.