Coastcom D/I Mux III System User Manual page 53

Chapter 1. System Overview and Modes of Operation
Figure 1-14. Line Interface Unit Block Diagram
LIU Network Loop Switch
The LIU Network Loop switch sends a standard loopback code to another D/I Mux III or
Channel Service Unit (CSU) at the remote end. After a network loop is established, the
information sent to the remote end will return to the local D/I Mux III as a loopback. The
LIU Network Loop only functions when a Dual CSU Interface is installed.
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