Maintenance
4-153160-A2-GB21-50 January 1997
Test Commands
The test commands enable you to run loopbacks and
test patterns on the DSU/CSU, and to test the front panel
LEDs. These tests can help you isolate areas of trouble if
you are having problems with your DSU/CSU.
To access all Test commands from the Test branch,
press F2 to select Test from the top-level menu screen.
F1
DSU ESF
Stat Test Cnfig
F2 F3
Remote Loopback Tests
The Remote Loopback tests enable you to troubleshoot
your circuit by sending the following to a far-end device:
For Networks
•Line loopback up activation sequence for
10 seconds (LLBUP)
•Line loopback down activation sequence for
10 seconds (LLBDN)
For Channels
•V.54 activation sequence to initiate a V.54 Loop 2
(54UP)
•V.54 deactivation sequence to terminate a V.54
Loop (54DN)
•ANSI T1.403 (Annex B) activation sequence to
initiate a DCLB on the remote device (FT1UP)
•ANSI T1.403 (Annex B) deactivation sequence to
terminate a DCLB on the remote device (FT1DN)
You cannot perform remote loopbacks if any of the
local loopbacks are active. If you attempt to do so, the
error message Invld Test Combo (Invalid Test
Combination) appears.
NOTE
The following procedures are
examples only. Screen displays
may vary depending on the
model and configuration of the
DSU/CSU.

Sending a Line Loopback Up or Down

To send a Line Loopback Up or Down sequence on the
network to a far-end DSU/CSU,
1. From the top-level menu screen, select Test.
2. From the Test screen, select Rlpbk.
F1
Test:
Rlpbk Lpbk Ptrns
F2 F3
3. From the Rem Loopback screen, press F1 to select
LLBUP (Line Loopback Up), or press F2 to select
LLBDN (Line Loopback Down).
F1
Rem Loopback:
LLBUPLLBDN 54UP
F2 F3
The Line Loopback sequence is sent up or
downstream to the far-end DSU/CSU for
10 seconds. During this time, Sending appears on
Line 2 of the LCD, followed by Command
Complete when 10 seconds have elapsed.
You can press any function key to restore the Rem
Loopback screen without affecting transmission of
the loopback code.