B-1
3910-A2-GN32-40
September 1998
Troubleshooting
Overview
This appendix points out basic problems that can occur when operating a 391x Series modem.
Use Tables B-1 through B-6 to check out these problems. If you are having data communication
difficulties, such as periodic character loss, random errors, or constant format errors, use the
loopback tests described in Chapter 8, Test Branch. With these tests you can usually isolate the
fault in your system by using the process of elimination. If problems continue to occur, contact
your service representative.
Table B-1
Modem Health
Symptom
Action
The modem did not pass the
power-up self-test.
Contact your service representative.
The power LED does not light or
the LCD does not display
information.
Make sure the modem’s ON/OFF switch is in the ON position.
Make sure the power supply is connected to the dc power receptacle
on the modem.
If the Power LED and/or LCD do not operate, contact your service
representative.
A problem is suspected after the
power-up self-test.
Perform a self-test via the modem’s DCP or type AT&T9 if using AT
commands.
Perform a local analog loopback with a Pattern test. If the modem
consistently registers errors, contact your service representative.
If the modem passes the above tests and a problem still exists, then
the problem is probably not with your modem.
B
