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CHAPTER 6: Troubleshooting
6. Troubleshooting
This chapter contains information about how to test your system, how to isolate
faults, and what to do when you find problems.
6.1 Loopback Testing
With the LDM-MR19.2’s test switches and LEDs, you can rapidly check the unit
itself and its attached data terminals and telephone lines. Use the checkout
procedures described in this section to verify normal system operation and isolate
faulty equipment in the event of failure.
Before you test the operation of your equipment and line circuits, be sure all
units are ON and configured normally.
6.1.1 M
ODEM
T
EST
: A
NALOG
L
OOPBACK
This test checks the performance of the local modem, the local data terminal, and
the cables between these two devices (see Figure 6-1 on the next page). Perform
the test separately at the local and remote sites.
1. Press the ANA (Analog Loopback) pushbutton on the front panel of the unit
you want to test. The TEST LED should light. The LDM-MR19.2’s transmit
output is now connected to its own receiver.
2. Verify that the data-terminal equipment (DTE) is operating properly and can
be used for testing. If you find a fault, call a technician or replace the unit.
3. Set the DTE equipment to half-duplex to get an “echo” through the system,
or use a special Bit Error Rate Tester (BERT).
4. If BERT equipment indicates no faults, but the data terminal itself does
indicate one, follow the manufacturer’s checkout procedures for the data
terminal. Also check the interconnecting cabling between the data terminal
and the LDM-MR19.2.
5. After completing the test at both ends, press the ANA pushbutton again to
restore it to the OFF position. Proceed with the Communication-Link Tests.
