MultiModemDSVD User Guide 5 Solving Problems
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The Modem Does Not Respond to Commands
Make sure the modem is plugged in and turned on. (See “None of the Indicators
Light.”)
Make sure you are issuing the modem commands from the data communications
software, either manually in terminal mode or automatically by configuring the
software. (You cannot send commands to the modem from the DOS prompt.)
Make sure you are in terminal mode in your data communications program, then
type AT and press ENTER. If you get an OK response, your connections are good
and the problem likely is in the connection setup in your communications software.
Try resetting your modem by turning it off and on. If you are using DOS or Win-
dows 3.1 communications software, make sure the initialization string includes
&F as the first command, to cancel any “leftover’ command that could affect the
modem’s operation.
If you don’t get an OK, the problem may still be in the communications software.
Make sure you have done whatever is necessary in your software to make a port
connection. Not all communications programs connect to the COM port automat-
ically. Some connect when the software loads and remain connected until the
program terminates. Others can disconnect without exiting the program. The
modem’s TR indicator lights to show that the software has taken control of the
modem through the COM port.
Your communications software settings may not match the physical port the modem
is connected to. The serial cable might be plugged into the wrong connector—check
your computer documentation to make sure. Or you might have selected a COM
port in your software other than the one the modem is physically connected to—
compare the settings in your software to the physical connection.
If the modem is on, the cable is plugged into the correct port, the communica-
tions software is configured correctly, and you still don’t get an OK, the fault
might be in the serial cable. Make sure it is firmly connected at both ends.
Is this the first time you have used the cable? If so, it may not be wired correctly.
Check the cable description on the packaging to make sure the cable is the right
one for your computer.
Peripheral expansion cards, such as sound and game cards, might include a seri-
al port preconfigured as COM1 or COM2. The extra serial port, or the card itself,
may use the same COM port, memory address, or interrupt request (IRQ) as
your communications port. Be sure to disable any unused ports.
Windows 3.1x: To look for address or IRQ conflicts, in Program Manager select
File | Run, type MSD, and press ENTER. Then select Mouse, COM Ports, and
IRQ Status, and note the addresses and IRQs that are in use. If you find an IRQ
conflict, note which IRQs are not being used, then change one of the conflicting
devices to use one of the unused IRQs. If you find an address conflict, change the
address of one of the conflicting devices.
To change a port address or IRQ in Windows 3.1x, double-click the Control Panel
icon, then the Ports icon. Click on the port you want to change, click Settings,
click Advanced, and select the new port address and/or interrupt. If you wish to
use COM3 or COM4, note that COM3 shares an IRQ with COM1, as does COM4
with COM2, so you should change their IRQs to unused ones, if possible.