Paradyne Comsphere 3920Plus Installation And Operation Manual page 214

Symptom
The modem does not accept or echo
back AT commands.
3920-A2-GN31-10
Table B-4
Modem — DTE Connection
Verify that the cable between the Async port of the DTE and the modem is a
standard RS-232 cable. (Null modem cables, also known as crossover cables,
do not work in this application.)
Verify that the Command Character Echo configuration option is enabled. Refer
to DTE Dialer in Chapter 4.
Verify that the DTE Dialer Type configuration option is set to AT. Refer to DTE
Dialer in Chapter 4.
Verify that the Result Codes configuration option is enabled. Refer to DTE
Dialer in Chapter 4.
Reload the Async Dial factory configuration area to guarantee that all
configuration options are returned to their proper setting.
Make sure that all AT commands are terminated with a carriage return.
Verify that the Carriage Return Character configuration option matches what is
used by the DTE. Refer to DTE Dialer in Chapter 4.
Verify that the DTE has a valid character format. Valid format consists of 8 data
bits with no parity or 7 data bits with even, odd, mark or space parity.
Verify that the DTE's data rate is supported by the modem. Refer to the Async
DTE Rate configuration option in the DTE Interface section of Chapter 4.
If using a PC, verify that the modem is attached to the correct communications
port.
April 1995
Action
Troubleshooting
B-3