Troubleshooting
B-5
3910-A2-GN32-40
September 1998
Table B-5
(2 of 2)
Modem — VF Connection
Symptom
Action
The modem does not go off-hook
and begin dialing.
If using AT Dialing, refer to Table B-4, Modem—DTE Connection.
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.
If using V.25bis HDLC, verify that the character format uses flag,
address, and control characters before the text block and a frame
sequence check and flag after the text block.
The modem dials but does not
connect.
If the modem is operating behind a PBX, determine if a 9 and comma
are needed before the telephone number.
Verify whether Tone or Pulse dialing is needed.
Verify that both modems are configured the same in regard to Error
Control. Try calling in Buffer mode.
If both modems use V.32bis or V.32 modulation, try setting the
modem’s V.32bis Train configuration option to Long.
Intermittent disconnects, high
error rates, or excessive
retransmissions occur.
Perform an End-to-End test. Refer to Pattern in Chapter 8, Test
Branch.
The modem establishes and
then disconnects the call.
You may have a poor VF connection. Try dialing again.
The remote modem may have encountered an error control (EC)
disconnect. 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.
Check the LCD to determine the reason for the disconnect.
Perform a Local Analog Loopback test.
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.
