Coastcom D/I Mux III System User Manual page 212

Chapter 5. Diagnostics
Dual Channel Bank: T1-2 Line Loopback
Line Loop Set code received on the input of span A causes PCM to be looped back out
the output of span B. Output PCM from LIU A is sent to the output of span A. PCM from
the input of span B and the output of LIU B are blocked. Reference Figure 5-20.
Figure 5-20. Dual Channel Bank: T1-2 Line Loopback
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