4.If the BERT test indicates no errors are present, move the “511/E—511” toggle switch to the left-hand position to activate the “511/E” test with periodic errors. If this test is working properly, the Error LED will blink regularly. A successful 511/E test will confirm that the loop is in place, and that the Multi-Function LD Card’s built-in 511 generator and detector are working properly.
5.If the remote BERT test indicates that errors are present, but the local analog loopback BERT tests showed that both Multi-Function LD Cards were functioning properly, there is probably a problem with the twisted- pair communication line connecting the two modems. A common problem is improper crossing of the pairs. Also, check the cable’s pinning (see Section 4.5) and continuity. If you still get errors and can’t find the cause, call your supplier for technical support (see Section 6.1).
5.4.3USING THE V.52 BERT TEST INDEPENDENTLY
The Multi-Function LD Card can perform its V.52 BERT test independently of the V.54 loopback tests. This requires two operators: one to initiate and monitor the test at the local Card, and one to do the same at the remote Card. To use the V.52 BERT test by itself, both operators should simultaneously follow these steps:
1.Move the lower front-panel toggle switch labeled “511/E—511” to the “511” (right-hand) position. This will activate the V.52 BERT test mode and transmit a 511 test pattern to the other unit. If any errors are present, the receiving modem’s Error LED will blink sporadically.
NOTE
For this independent test to work properly, the “511/E—511” switch on both Multi-Function LD Cards must be set the same way (that is, moved to the “511” position for this step and to the “511/E” position for the next step).
2.If the BERT test indicates no errors are present, move the “511/E—511” toggle switch to the left-hand position to activate the “511/E” test with periodic errors. If this test is working properly, the receiving modem’s Error LED will blink regularly. A successful 511/E test will confirm that the link is in place, and that the Multi-Function LD Cards’ built-in 511 generators and detectors are working properly.
