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LTPH-UM-1138-02, Issue 2
To perform the GNLB loopback test procedure:
1
Have the CO tester send the NREM (3-in-7) inband loopup code for 5 seconds. You should observe the
NREM message on the front-panel display. (The Status LED on the front panel should be green, and the
loopback mode should also be identified on the Monitor screen.)
2
Have the CO tester transmit a DS1 test signal towards the H4TU-C and verify that the returned (looped) signal
to the test set is error-free.
3
If step 2 fails, have the CO tester transmit the (3-in-5) inband loopdown code.
4
Have the CO tester send the NLOC (4-in-7) inband loopup for 5 seconds. You should observe the NLOC
message on the front-panel display. (The Status LED on the front panel should be yellow, and the loopback
mode should also be identified on the Monitor screen.)
5
Repeat Step 2. If the test passes, the problem is in the downstream direction. If it fails, the problem is in the
upstream direction.
A3LB Test Procedure
The H4TU-C-231 List 1 can be looped back by sending the Addressable Office Repeater (AOR) LPBK activation
code 1111-1111-0001-1110 (FF1E) for at least 5 seconds. This causes the H4TU-C to enter the NLOC state. The
Loopback Time-Out setting (see
of this loopback unless it is overridden by the reception of a second identical 16-bit loopup command before the
timer expires. When this time-out override state exists, the only way to loop the H4TU-C down is to issue one of
the three loopdown commands listed in
loopback sessions.
Table 17
summarizes the codes required to execute an A3LB Addressable Repeater Loopback command. All code
sequences must be present for at least 5 seconds.
Name
Binary Code
NLOC
1111-1111-0001-1110 (FF1E)
CREM
0011-1111-0001-1110 (3F1E)
NREM
1111-1111-0000-0010 (FF02)
NDU1
1111-1111-0000-0100 (FF04)
CDU1
0011-1111-0000-0100 (3F04)
NDU2
1111-1111-0000-0110 (FF06)
CDU2
0011-1111-0000-0110 (3F06)
D1LB
D2LB
CLOC
0011-1111-0000-0010 (3F02)
SMJK
11000-11000-11000 ...
SMJK
100000 100000 100000 ...
SMJK
1111-1111-0100-1000 (FF48)
Loopdown
11100-11100-11100 ...
Loopdown
100-100-100 ...
Loopdown
1111-1111-0010-0100 (FF24)
(a) The leftmost bit arrives first in all sequences. The detection algorithm functions reliably with a random 10
(BER) on the facility. The entire arming and loopback sequence can also be initiated at the remote H4TU-R location.
H4TU-C-231 List 1
"Setting the Loopback Time-Out Option" on page
Table
17. The automatic time-out mode is restored during subsequent
Table 17. A3LB Addressable Repeater Loopback Commands
(a)
(Hexadecimal Equivalent)
September 12, 2003
Description
H4TU-C loopup from NI.
H4TU-C loopup from CI.
H4TU-R loopup from NI.
Signal is looped back to the network at H4D1.
DS1 signal from customer is looped back to the customer at H4D1.
Signal is looped back to the network at H4D2.
DS1 signal from customer is looped back tot he customer at H4D2.
Dual loopback at H4D1.
Dual loopback at H4D2.
H4TU-R loopup from CI.
H4TU-R loopup from NI.
H4TU-R loopup from NI.
H4TU-R loopup from NI (ESF-DL).
H4TU-C and H4TU-R loopdown from NI OR CI.
H4TU-C and H4TU-R loopdown from NI OR CI.
H4TU-C and H4TU-R loopdown from NI OR CI (ESF-DL).
Testing
49) determines the duration
-3
Bit Error Ratio
53
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