Testing | LTPH-UM-1031-03, Issue 3 |
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To perform the GNLB loopback test procedure:
1Have 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.)
2Have 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.
3If step 2 fails, have the CO tester transmit the (3-in-5) inband loopdown code.
4Have 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.)
5Repeat 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-319 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 “Setting the Loopback Time-Out Option (LBTO)” on page 48) determines the duration 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 Table 17. The automatic time-out mode is restored during subsequent 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.
Table 17. A3LB Addressable Repeater Loopback Commands
Name | Binary Code (a) (Hexadecimal Equivalent) | Description |
NLOC | 1111-1111-0001-1110 (FF1E) | H4TU-C loopup from NI. |
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CREM | 0011-1111-0001-1110 (3F1E) | H4TU-C loopup from CI. |
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NREM | 1111-1111-0000-0010 (FF02) | H4TU-R loopup from NI. |
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NDU1 | 1111-1111-0000-0100 (FF04) | Signal is looped back to the network at H4D1. |
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CDU1 | 0011-1111-0000-0100 (3F04) | DS1 signal from customer is looped back to the customer at H4D1. |
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NDU2 | 1111-1111-0000-0110 (FF06) | Signal is looped back to the network at H4D2. |
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CDU2 | 0011-1111-0000-0110 (3F06) | DS1 signal from customer is looped back tot he customer at H4D2. |
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D1LB | | Dual loopback at H4D1. |
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D2LB | | Dual loopback at H4D2. |
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CLOC | 0011-1111-0000-0010 (3F02) | H4TU-R loopup from CI. |
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SMJK | 11000-11000-11000 ... | H4TU-R loopup from NI. |
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SMJK | 100000 100000 100000 ... | H4TU-R loopup from NI. |
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SMJK | 1111-1111-0100-1000 (FF48) | H4TU-R loopup from NI (ESF-DL). |
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Loopdown | 11100-11100-11100 ... | H4TU-C and H4TU-R loopdown from NI OR CI. |
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Loopdown | 100-100-100 ... | H4TU-C and H4TU-R loopdown from NI OR CI. |
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Loopdown | 1111-1111-0010-0100 (FF24) | H4TU-C and H4TU-R loopdown from NI OR CI (ESF-DL). |
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(a)The leftmost bit arrives first in all sequences. The detection algorithm functions reliably with a random 10-3Bit Error Ratio (BER) on the facility. The entire arming and loopback sequence can also be initiated at the remote H4TU-R location.
