Metrodata FM4900, User Manual

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TEST & TROUBLESHOOTING
53 76-02-011F
9 . 2. 2 DTE External Loop
When the EXTERNAL LOOP is ENABLED the FM4900 uses one of the HSSI control lines
(LC) to put the local DTE into loop.
This validates the E3 link, both FM4900’s and both sets of DTE cables if the remote DTE
recognises its own signals.
Note that if EXTERNAL LOOP CONTROL is DISABLED, the remote loop code receiver in
the DSU is inhibited, so the FM4900 will not accept remote loop commands from other DSUs
on the network. The HSSI control lines LA and LB are also inhibited.
Figure 9. 3 DTE External loop test
HSSI
HSSI