User's Manual

CHAPTER 6: Troubleshooting

6. Troubleshooting

This chapter explains system-test and fault-isolation procedures.

The line driver provides local loopback and remote digital loopback in compliance

with the V.54 standard. Unless you disable them, the unit’s loopback tests can be

activated manually from the unit’s front panel, and the local analog and remote

digital loopbacks can be activated electronically through the DTE connection.

6.1 Loop Tests

The loop-test buttons (DIG, ANA, and REM) and LEDs built into the line driver

allow you to rapidly check the unit, the attached cables, and the attached DTEs.

Use the test procedures described in this chapter to verify normal system operation

and to isolate faulty equipment if a failure occurs. (Before testing the operation of

the system equipment and line circuits, make sure that all devices are turned on

and are properly configured.)

6.2 The Bit-Error-Rate Tester (BERT)

You can activate the line driver’s internal Bit Error Rate Tester in any diagnostics

test in which the transmitted test pattern is looped back to the BERT for

comparison. An example is shown in Figure 6-1 on the next page.

The line driver is also capable of operating opposite any 511 BERT tester. When

you use one line driver opposite another, either with one or both PATT buttons

pressed (see Figure 6-2) or with an external BERT transmitting the same V.52 (511-

bit) pattern, you can test the complete link. To activate the BERT, press the PATT

button. The ERR LED will light momentarily, just to confirm that the LED is

working, and then the test will proceed. If errors are detected, the ERR LED will be

continuously lit (if the errors are continuous) or will blink (for intermittent

errors).

NOTE

For the line driver’s BERT to operate correctly, the CARRIER jumper

must be set to ON or the RTS signal must be high.

While PATT is pressed, the V.35 interface is functionally disconnected.