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Chapter 4 Problems and Solutions 21
The modem works well when you are not using data compression,
but the compression features are inoperative.
28
General Troubleshooting
Problem: Your modem seems to install under Windows
95 or 98, but Windows cannot find it later.
Solution: If your computer has a built-in modem on the
motherboard, Windows may reinstall it the next
time you start up. Consult your computer’s
documentation or call your computer’s manu-
facturer to get instructions on how to disable
the built-in modem.
Problem: The software cannot find the modem and the
modem does not respond to AT commands.
(The following comment applies to many
other problems as well.)
Solution: The most common error with modems is that
the communications software is not configured
for the same COM port as the modem. Check
which COM port the modem is using. Make
sure that the software’s COM port setting
matches the modem’s COM port setting.
Another problem is that COM port resources
may be in use by another device. Make sure
that the COM port resources used by the mo-
dem are not being used by any other device,
such as a soundcard.
Problem: You type an AT command line in a terminal
application and press Enter, but your mo-
dem fails to execute the command line. Or
there was no response after executing a
command.
Solution: Be sure you type AT at the beginning of the
command line.
Make sure the communications software is con-
figured for the same COM port as your modem.
Be sure your modem is not in data mode when
you type the command. Use the escape char-
acter sequence to switch to terminal mode. (The
default escape sequence is to wait at least one