US Robotics 33600 User Manual page 26

The modem does not
respond when, in
terminal mode, you
send AT commands.
The modem cannot
make a call and sends
the message 'NO DIAL
TONE'.
The modem cannot
make a call when
connected to a PBX.
22 Sportster Winmodem 33600 & x2/56K - User's manual
Check that the COM port to which the
modem is connected is properly
declared. Check the IRQ configuration in
the communications software or in the
Windows Control Panel. Check that
the application is in terminal mode.
If none of the preceeding solutions solve
the problem, it means that the modem is
certainly in conflict at the COM port/IRQ
level. Begin the installation procedure in
the Installation chapter. If you change
the COM/IRQ configuration, don't forget
to make these changes in the application
as well.
Check the connection to the telephone
line. It could be that the modem cannot
detect the dial tone.
Try the ATX3DT<phone number> dial
sequence.
A pause in dialing may be needed to
allow time to connect to the outside
PSTN line. An example of dialing an
outside line is shown below, where a 9 is
used to access the outside line and a
comma causes a pause in the dialing
sequence.
$7' 
The value of register S8 may be
adjusted to give the required delay, or
use a W in place of a comma. The W
causes the modem to wait for a second
dial tone before continuing and may
result in faster dialing.