User guide

Chapter 6 – Troubleshooting
26 Multi-Tech Systems, Inc. MT9234ZBA-Series User Guide
● Make sure you are in terminal mode in your data communication program, then type AT and press Enter. If
you get an OK response from your modem, your connections are good and the problem likely is in the
connection setup in your communication software.
● If you don’t get an OK, the problem may still be in the communication software. Make sure you have done
whatever is necessary in your software to make a port connection. Not all communication programs connect
to the COM port automatically. 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 communication software settings may not match the physical port to which the modem is connected.
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 communication 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 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.
● 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 might have a problem beyond the scope of this user guide. If you have another Multi-Tech
modem, try swapping modems. If the problem goes away, the first modem is possibly defective.
The Modem Cannot Connect When Dialing
There can be several reasons the modem fails to make a connection. Possibilities include
● lack of a physical connection to the telephone line.
● a wrong dial tone.
● a busy signal.
● a wrong number.
● no modem at the other end.
● a faulty modem, computer, or software at the other end.
● incompatibility between modems
● poor line conditions.
You can narrow the list of possibilities by using extended result codes. Extended result codes are enabled by
default. If they have been disabled, include V1X4 in the modem’s initialization string, or in terminal mode enter
ATV1X4 and press Enter. When you dial again, the modem reports the call’s progress.
● If the modem reports NO DIALTONE, check that the modem’s telephone line cable is connected to both the
modem’s LINE jack (not the PHONE jack) and the telephone wall jack. If the cable looks secure, try replacing
it. If that doesn’t work, the problem might be in your building’s telephone installation. To test the building
installation, plug a telephone into your modem’s telephone wall jack and listen for a dial tone. If you hear a
dial tone, your modem might be installed behind a corporate phone system (PBX) with an internal dial tone
that sounds different from the normal dial tone. In that case, the modem might not recognize the dial tone