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 BERT test indicates that errors are present, make sure that the RS- 232 cable connecting the DTE to the Multi-Function LD Card is wired straight-through, and is plugged in properly. Also, make sure that the Card is configured properly. Then recheck your DTE equipment. If you still get errors and can’t find the cause, call your supplier for technical support (see Section 6.1).
5.4.2REMOTE DIGITAL LOOPBACK (RDL)
The Remote Digital Loopback (RDL) test checks the performance of both the local and remote Multi-Function LD Cards, and the communication link between them. Any characters sent to the remote Card in this test mode will be echoed (returned) back to the originating device. For example, characters typed on the keyboard of the local terminal will appear on the local terminal’s screen after having been passed to the remote Multi-Function LD Card and looped back. To perform an RDL test, follow these steps:
1.Activate RDL. You can do this in either of two ways. One is to move the upper front-panel toggle switch labeled “Remote—Analog” to the “Remote” (left-hand) position. The other is to raise the signal on
Pin 21 of the RS-232 interface (switch S3 position 6 must be “On”—see Section 3.1.4). Once RDL is activated, the remote Card’s receive input is connected to its own transmitter. The Test LED should light on both Cards.
2.Verify that the DTE attached to the local Card is operating properly and can be used for a test.
3.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 inject a 511 test pattern into the remote loop. If any errors are present in the loop, the Error LED will blink sporadically.
