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COMSPHERE 3821Plus Modem
C-2 February 1998 3821-A2-GB20-30
Table C-2
Online Operation
Symptom
Action
Data scrambled or
unreadable
Verify that the character format (data bits, parity, and stop bits) is set to the same value in
both modems.
Missing data during a
transfer
Verify that you are using the same method of flow control for both the modem and the DTE.
transfer
If using XON/XOFF flow control, verify that the modem’s parity matches the DTE’s parity.
Table C-3
Leased-Line Operation
Symptom
Action
Modems do not train-up on
leased lines
Verify that the correct cabling is used for your application. Refer to Chapter 2 for modem
installation instructions.
Verify that one modem is configured for Answer mode and the other is configured for
Originate mode.
Table C-4
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.)
Using the SDCP, reload the Async Dial factory configuration area to guarantee that all
configuration options are returned to their proper setting.
If an SDCP is not available, use the AT command recovery technique in Chapter 4.
Modem does not accept or
echo back AT commands
Make sure that all AT commands are terminated with a carriage return.
echo back AT commands
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.