5.3 TEST MODES
The Model 1140RC offers two V.54 test modes and two V.52 test
modes to evaluate the condition of the modems and the communication link. Both sets of tests can be activated physically from the front panel. The V.54 test can also be activated from the
V.54 and V.52 test modes on the Model 1140RC are available for point-
5.3.1 LOCAL ANALOG LOOPBACK (LAL)
The Local Analog Loopback (LAL) test checks the operation of the local Model 1140RC, and is performed separately on each unit. Any data sent to the local Model 1140RC in this test mode will be echoed (returned) back to the user device. For example, characters typed on the keyboard of a terminal will appear on the terminal screen. To perform a LAL test, follow these steps:
1.Activate LAL. This may be done in one of two ways: First, by moving the upper front panel toggle switch RIGHT to “Analog”. Second, by raising pin 18 on the
2.Verify that the data terminal equipment is operating properly and can be used for a test.
3.Locate the lower of the two toggle switches on the front panel of the Model 1140RC and move it to the right. This will activate the V.52 BER test mode and inject a “511” test pattern into the local loop. If any errors are present in the loop, the red “Error” LED will blink sporadically.
4.If the BER test indicates no errors are present, move the V.52 toggle switch to the left, thus activating the “511/E” test with periodic errors. If the test is working properly, the red “Error” LED will light. A successful “511/E” test will confirm that the loop is in place, and that the Model 1140RC’s
5.If the BER test indicates that errors are present, check to see that the
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5.3.2 REMOTE DIGITAL LOOPBACK (RDL)
The Remote Digital Loopback (RDL) test checks the performance of both the local and remote Model 1140RCs, and the communication link between them. Any characters sent to the remote 1140RC in this test mode will be returned back to the originating device. For example, characters typed on the keyboard of the local terminal will appear on the local terminal screen after having been passed to the remote Model 1140RC and looped back. To perform an RDL test, follow these steps:
1.Activate RDL. This may be done in two ways: First, by moving the upper front panel toggle switch LEFT to “Remote”. Second, by raising pin 21 on the
2.Verify that the DTE equipment on the local end is operating properly and can be used for a test.
3.Locate the lower of the two toggle switches on the front panel of the 1140RC and move it to the right. This will activate the V.52 BER test mode and inject a “511” test pattern into the remote loop. If any errors are present in the loop, the red “Error” LED will blink sporadically.
4.If the BER test indicates no errors are present, move the V.52 toggle switch to the left, thus activating the “511/E” test with periodic errors. If the test is working properly, the red “Error” LED will light. A successful “511/E” test will confirm that the loop is in place, and that the Model 1140RC’s
5.If the remote BER test indicates that errors are present, and the local analog loopback/BER tests showed that both Model 1140RCs were functioning properly, this suggests a problem with the twisted pair communication line connecting the two modems. A common problem is improper crossing of the pairs. Also, verify that the modular connections are pinned properly, and the twisted pair line has continuity. If you still have errors, call Technical Support at (301)
5.3.3USING THE V.52 BER TEST INDEPENDENTLY
The Model 1140RC's V.52 BER test can be used independent of the V.54 loopback tests. This requires two operators: one to initiate and monitor the test at both the local and the remote Model 1140RC. To use the V.52 BER test by itself, both operators should simultaneously follow these steps:
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