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CHAPTER 5: Operation and Diagnostics
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).
5.4.3 U
SING THE
V.52 BERT T
EST
I
NDEPENDENTLY
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.