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Testing
7-2
7924-A2-GB20-30
October 1997
Local Loopbacks
H When a local loopback is enabled, the red Loop Bk LED on the front panel of
the initiating unit lights up and remains lit until the loopback is disabled.
H The data flow is indicated by the bold thick arrows in Figures 7-1 and 7-2.
H When the CO initiates a local loopback, an Alarm Indication Signal (AIS) is
received at the CP end (only if the CP end is G.703-compatible). (AIS is not
received at V.35-compatible CP units.)
Terminal
97-15514-01
CO CP
E1 HDSL
7900
7900
E1 HDSL
7900
7900
Diagnostic
Equipment
Diagnostic
Equipment
Loop Bk
LED lights
AIS
AIS = Alarm Indication Signal
Figure 7-1. Local Loopback, Initiated at the CO Unit
Terminal
97-15518-01
CO CP
E1 HDSL
7900
7900
Diagnostic
Equipment
E1 HDSL
7900
7900
Diagnostic
Equipment
Loop Bk
LED lights
Figure 7-2. Local Loopback, Initiated at the CP Unit