Coastcom D/I Mux III System User Manual

Chapter 5. Diagnostics
185
Drop-and-Insert: Line Loopback
Line loopback is set in response to receiving the “Line Loop Set” code on a span's input. PCM
arriving at the input is looped back to the opposite span's output. The LIUs are not in the PCM
path. T1 line receivers and line build outs are kept in the PCM loop to maintain the proper T1 line
levels. In line loopback, the PCM is looped before reaching the LIUs
Drop-and-Insert: T1-1 Line Loopback
Line Loop Set code received on the input of span B causes span B input PCM to be
looped back out span A before reaching the LIUs, as well as passing it on to the input of
LIU B. Output PCM from LIU B is sent to the output of span B. PCM from the input of
span A is unaffected, as depicted in Figure 5-13. The output of LIU A is blocked.
Figure 5-13. Drop-and-Insert: T1-1 Line Loopback

Coastcom D/I Mux III System Specifications

General

Brand	Coastcom
Model	D/I Mux III System
Category	Multiplexer
Language	English