COMSPHERE 3825Plus Modem
B-4
November 1996
3825-A2-GB30-20
Table B-4
(3 of 3)
Modem – VF Connection
Symptom
Action
Modem establishes and
disconnects a call
You may have a poor VF connection. Disconnect and dial again.
disconnects a call
The remote modem may have encountered an EC Disconnect, where the modem is
configured to establish a call using error correction.
If the modems cannot negotiate EC, then a disconnect occurs.
The remote modem may be in a forced Error Control mode (disconnect if there is no error
control). Reconfigure your modem to V.42/MNP or Buffer and try again.
Perform a Local Analog Loopback test to check the modem’s hardware operation.
High error rates occur when
running a local loopback or
self-test
Incoming rings can cause data errors during a loopback test. Abort the test, disconnect the
modular VF cord, and restart the test.
Table B-5
Modem – DTE Connection
Symptom
Action
Modem does not accept or
echo back AT commands
Verify that the cable between the Async port of the DTE and the modem is a standard
RS-232 cable. If the cable is bad, replace it. (Null modem cables, also known as crossover
cables, do not work in this application.)
Reload the Async Dial factory configuration area to guarantee that all configuration options
are returned to their proper setting. Refer to the
Recovering AT Commands section in
Chapter 2.
Make sure that all AT commands are terminated with a carriage return.
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 set to a level supported by the modem
(115,200 bps–300 bps).
If using a PC, verify that the modem is attached to the correct communications port.
