This variable describes the variety of Zero Code Suppression used on the
link, which in turn affects a number of its characteristics. It should
be set to match the carrier.
AMI (alternate mark inversion) refers to a mode wherein no zero code
suppression is present and the line encoding does not solve the problem
directly. In this application, the higher layer must provide data
which meets or exceeds the pulse density requirements, such as inverting
HDLC data. This could be used for T1 or E1 lines.
B8ZS refers to the use of a specified pattern of normal bits and bipolar
violations which are used to replace a sequence of eight zero bits. This
can be used on T1 lines while HDB3 provides similar functionality for
E1 links.