LTPH-UM-1031-03, Issue 3 | Testing |
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•CDx? = Doubler 1 or Doubler 2, if H4D is available
•CLO? = CLOC
•COL? = Dual loopback at H4TU-C
•DxL? = Dual loopback at Doubler 1 or Doubler 2, if available
•RUL? = Dual loopback at H4TU-R
4Press SEL to activate the selected loopback. The previous loopback is terminated.
Once a loopback is selected and activated, the loopback stays active until it times out (based on the LBTO setting). When a loopback times out, the display returns to the normal display mode.
You can terminate loopbacks manually and exit the MAN LPBK mode by simultaneously pressing the MODE and SEL pushbuttons for 3 or more seconds. If no loopback is active, the MAN LPBK mode automatically terminates after 30 seconds.
All loopbacks can be initiated by inband commands in the DS1 payload or by a command from the HDSL4 system (front-panel pushbuttons or maintenance screen selections). Therefore, whenever a loopback is active, the method by which it was activated is indicated in the loopback and status information (Monitor screen) by the annotation HG or PL adjacent to the identified loopback. For example, NREM-HG indicates that the loopback was initiated by the HDSL4 system.
SMJK loopback commands are only activated by inband commands.
LOOPBACK TEST PROCEDURES
The following sections provide step-by-step test procedures for verifying the integrity of the HDSL4 channels at every module location as well as the DS1 channels to the customer and the local DSX-1 interface. Figure 29 on page 50 summarizes the available loopbacks in the system.
General Troubleshooting Tips
If trouble is encountered on the DSX-1 interface of the H4TU-C, verify that the:
•H4TU-C is making a positive connection with its shelf connector.
•H4TU-C internal equalizer is set to the correct distance range per Table 5 on page 19. All equalizers should be set to the distance from the DSX-1 to the shelf.
The transmit and receive DSX-1 ports have splitting access jacks and miniature, 210-series, bridging jacks as shown in Figure 1 on page 3. Connecting one cable between the two (BRG) jacks and another between the two LINE jacks splits the IN and OUT and creates metallic loopbacks towards both the DSX-1 and the H4TU-C-319. If separate plugs are inserted into both LINE jacks with the other end disconnected, the BRG jacks can be used to send and receive test patterns towards the DSX-1.
