User guide
Chapter 4 - Troubleshooting
Multi-Tech Systems, Inc. MT5656ZDX User Guide 17
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.
6. If the modem is on, the cable is plugged into the correct port, the communications program is configured
correctly, and you still don’t get an OK, the fault might be in the serial cable. Verify it is firmly connected at
both ends.
7. 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 Verify the cable is the right one for your computer.
8. Peripheral expansion cards, such as sound and game cards, might include a serial 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 communication port. Be sure to disable any unused ports.
9. Windows 9x and 2000: Right-click on My Computer, select Properties from the menu, click on the Device
Manager tab, double-click on Ports, then double-click on the communication port your modem is connected
to. In the port’s Properties sheet, click on the Resources tab to see the port’s input/output range and
interrupt request. If another device is using the same address range or IRQ, it appears in the Conflicting
Device List. Uncheck Use automatic settings to change the port’s settings so they do not conflict with the
other device, or select the port the conflicting device is on and change it instead. If you need to open your
computer to change switches or jumpers on the conflicting device; refer to the device’s documentation.
The serial port might be defective. If you have another serial port, install the modem on it, change the COM port
setting in your software, and try again.
The modem may be defective. If you have another Multi-Tech modem, try swapping modems. If the problem goes
away, the first modem may be defective. Call Technical Support for assistance.