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Chapter 5 – Troubleshooting
Multi-Tech Systems, Inc. MT5656ZDX User Guide 19
The Modem Dials But Cannot Connect
There can be several reasons the modem fails to make a connection. Possibilities include:
• Lack of a physical connection to the telephone line.
• A missing 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.
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 DIAL TONE, check that the modem’s phone line cable is connected to both
the modem’s LINE jack (not the PHONE jack) and the phone wall jack. If the cable looks secure, try
replacing it. If that doesn’t work, the problem might be in your building’s phone installation. To test the
building installation, plug a phone into your modem’s phone 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 and might treat it as an error. Check your PBX manual to see if you can change the internal
dial tone; if you can’t, change your modem’s initialization string to replace X4 with X3, which will
cause the modem to ignore dial tones (note, however, that X3 is not allowed in some countries, such as
France and Spain).
• If the modem reports BUSY, the other number might be busy, in which case you should try again later, or it
might indicate that you have failed to add a 9, prefix to the phone number if you must dial 9 for an outside
line.
If you must dial 9 to get an outside line, the easiest way to dial it automatically is to include it in the
modem’s dial prefix, e.g., ATDT9. Note the comma, which inserts a pause before the number is dialed. By
inserting 9, into the dial prefix, you do not have to include it in each directory entry.
• If the modem reports NO ANSWER, the other system has failed to go off-hook, or you might have dialed a
wrong number. Check the number.
• If the modem reports NO CARRIER, the phone was answered at the other end, but no connection was
made. You might have dialed a wrong number, and a person answered instead of a computer, or you might
have dialed the correct number but the other computer or software was turned off or faulty. Check the
number and try again, or try calling another system to make sure your modem is working. Also, try
calling the number on your telephone. If you hear harsh sounds, then another modem is answering
the call, and the modems might be having problems negotiating because of modem incompatibilities or
line noise. Try connecting at a lower speed.