Troubleshooting
B-3
3825-A2-GB30-20
November 1996
Table B-4
(2 of 3)
Modem – VF Connection
Symptom
Action
Modem goes off-hook,
answers, but does not
connect (continued)
Verify that originating modem supports your modem’s modulation schemes. The 3825
Plus
modem recognizes V.34, V.32
terbo, V.32bis, V.32, V.22bis, V.22, V.21, Bell 212A, and
Bell 103J. It does not support other vendors’ proprietary modulation schemes.
Use the S41 register to force your modem to operate at the same modulation scheme as
the originating modem.
Originate Mode
Verify that the modem’s DTE Dialer configuration option is set to the correct setting: either
AT, DTR Dialing, V.25bis Async,V.25bis bisync, or V.25bis HDLC.
Modem does not go
off-hook and begin dialing
If using AT Dialing, refer to the Table B-5, Modem – DTE Connection.
off-hook and begin dialing
If using DTR Dialing, verify the telephone number stored in directory location 1, and verify
that the DTE is raising DTR from Off to ON to initiate a dial.
If using V.25bis Async, verify that the correct character format is set to 7 data bits with even
parity and 1 stop bit, and the carriage return and line feed are used as command
terminators.
If using V.25bis bisync, verify that the correct character format uses two synchronous
control characters and a start-of-text control character before the text block and an
end-of-text control character after the text block.
Modem does not go
off-hook and begin dialing
(continued)
If using V.25bis HDLC, verify that the correct character format uses flag, address, and
control characters before the text block and a frame sequence check and flag after the text
block.
Modem dials but does not
connect
If the modem is operating behind a PBX, verify if a 9 and comma are needed before the
telephone number.
Verify whether Tone or Pulse dialing is needed.
Verify if one modem is configured for Error Control or Disconnect and the other modem is
configured for no Error Control. Try calling in Buffer mode.
If both modems use V.32bis or V.32 modulation, set the modem’s V.32bis Train
configuration option to Long.
Intermittent disconnects,
high error rates, or
excessive retransmissions
Use the AT &T7 command to perform a remote digital loopback test with pattern test.
Modem connects but sends
ERROR result code to DTE
Your modem may be configured to use security and you are not supplying the proper
passwords. See
Security at the end of Chapter 4.
