AT&T MERLIN LEGEND Installation & Maintenance Manual page 89

System Description
B8ZS
B8ZS line coding encodes an all-zero channel octet into a unique
binary sequence with a "bipolar violation" in bit positions 4 and 7.
Normally, for bipolar (AMI) transmission, ones are encoded
alternately as a positive then negative, or negative then positive,
pulse. If two positive or two negative pulses are received in
succession, a bipolar violation occurs.
Ordinarily bipolar violations are caused by noise hits on the
signal. However, B8ZS line coding allows the 8-bit strings to be
detected at the receiving end and converted back into the
original sequence.
B8ZS line coding is preferred over ZCS because it does not
cause errors in data transmission.
B8ZS violations are passed by the ESF T1 CSU but not by other
CSUs. The CSU is a hardware component needed when two
endpoints are located in different buildings or when the distance
between the two endpoints makes office or line repeaters
necessary. The CSU is located on the customer's premises and
is used to connect the system to DS1 network facilities (see
"Install the Channel Service Unit" in Chapter 3, "Installation").
Line Compensation
Line compensation adjusts for the amount of cable loss in
decibels (dBs), based on the length of cable between the 100D
module and the CSU or other far-end connection point. The
factory setting is a value of 1, which allows a maximum loss of
0.6 dB. The other possible settings are shown in Table 1-11.
1-58 DS1 Capabilities