COMSPHERE 3800Plus Modems
C-2 October 1998 3980-A2-GB30-40
Table C-2Modem – 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.)
Verify that the Command Echo Character configuration option is enabled.
Refer to

Line Dialer

in Chapter 8,

Configure Branch

, or ATE command in
Chapter 13,
AT Commands and S-Registers
.
Verify that the DTE Dialer Type configuration option is set to AT. Refer to
DTE

Dialer

in Chapter 8, or the AT&M or AT&Q command in Chapter 13.
Verify that the Result Codes configuration option is enabled. Refer to
DTE

Dialer

in Chapter 8, or the ATQ command in Chapter 13.
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 ASCII value of a carriage return matches what is used by the
DTE and the modem. Refer to

DTE Dialer

in Chapter 8 or the S3 register in
Chapter 13. 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 your equipment can support the DTE data rate. Refer to Async
DTE Rate configuration option, in
DTE

Interface

in Chapter 8.
If using a PC, verify that the modem is attached to the correct
communications port.
Table C-3(1 of 2)Modem – VF Connection
Symptom Action
Modem does not receive a dial tone Attach the telephone directly to the wall outlet to verify that a dial tone exists.
Make sure the VF line is connected to the modem’s rear jack labeled Dial.
Modem does not go off-hook and answer
an incoming call Verify that the Auto-Answer Ring Count configuration option (S-Register 0) is
set to a value other than 0 (disable).
Verify that the DTE is providing DTR to the modem.
If the DTE does not provide DTR to the modem, verify that the modem’s DTR
Action configuration option is set for Ignore. Refer to

DTE Dialer

in Chapter 8.
Verify that all cables are attached to the correct connectors on the rear of the
modem.