6-2 61200290L1-1GSection 6, Loopbacks MX2800 M13 Multiplexer User Manual2. T1/E1 LOOPBACKSSelecting Data Mode Menu from the Loopback menu brings up the control menu shown in Figure 6-1. Ifinitiating a T1/E1 loopback, select the facility number (1-28). A loopback menu for the facility displays amenu of nine types of loopbacks. See Figure 6-2. Select Data Mode to end a loopback test in progress.Figure 6-2. Loopback Control MenuData ModeSelecting the Data Mode from the Loopback Control menu ends any loopback test in progress.TributaryA Tributary loopback loops the selected T1/E1 back to the network (DS3). The T1/E1 is demultiplexedthrough the M23 and M12/G.747 demultiplexers, looped back, and multiplexed back up through the M12/G.747 and M23 multiplexers. During this loopback, all network receive data is passed to the DSX-1/E1transmitters, but all data received by the DSX-1/E1 loop side is ignored and substituted with the networkdata. See Figure 6-3 for an illustration of this test.
