Checking the Dialer and the Telephone Lines

Once you are certain that the modem is receiving and responding to commands from the DTE, you can verify the modem dialing capabilities by attempting a call. This also tests the telephone lines.

Process
Check your communications software for the procedure to issue commands directly to the modem. The steps below explain how to place a call using the D command and various dialing modifiers.

Step 1:
First access the modem AT command state. When you receive an OK result code, instruct the modem to dial an actual telephone number (using the D command). If calling out of a PBX, remember to include the 9 or other outside access code in the phone number. Listen for a dial tone, followed by the tone dialing beeps. When these occur, they ensure you have entered the phone number correctly, and the local phone line is responding properly. If there is no dial tone, check the
phone line by dialing with an ordinary phone.

Note: Some PBX systems must be modified to produce at least 48 volts DC for the modem to work.

Step 2:
If you hear the phone on the other end ringing, then the remote phone is responding properly. Press any key to hang up.

Step 3:
Try dialing another modem to see if you make a connection. A connection is indicated by two whistling sounds of different tones (the carriers), followed by a hissing sound. The modem should respond with a CONNECT XXXXX result code.

Analysis
When you have reached this point successfully, both modems are performing correctly. If no errors occurred with these steps, the problem is related to software, user error, or improper modem installation/setup. If this procedure indicated a problem with the modems or the communication link, go to the next section. A common setting that might need to be changed is the response of the software or modem to the DTR signal (controlled by &D options).

You can check the modem answer capability (or when serving as the remote modem in the process above) by issuing the A command when the phone rings. The incoming call must be from a modem, however, not a voice call. The same sequence of carrier exchange is made.

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