Specifies that an interface is used in the carrier
environment of a T1 channel on a CT3 interface. The no version restores the default situation, in which an interface does
not operate in the carrier environment.
channel—One or more individual
T1 channels, ranges of T1 channels, or combination of individual channels
and ranges, in the range 1–28 (no spaces); for example, 3,7-15,19-13,27