How to test a modem for Caller Id support?

To use Mountain Systems Caller ID software products you need two things:

The first is required as only your local telephone company can supply this data. The second is required so that the data sent by the telephone company can be passed to software programs for processing.

Many current MODEMs offer support for Caller ID. The key question is always what setup string to use to enable Caller ID (virtually every MODEM disables Caller ID as the default).

For most MODEMs, the string AT#CID=1 will enable Caller ID. On some voice based MODEMs the string is AT#CLS=8#CID=1. Look in the user’s manual for your MODEM to see if any setup string is referenced or mentioned. Other common setup strings are:

The best way to test is to use a terminal data program. In Windows 3.X, the TERMINAL program (usually in the accessories folder) can be used. In Windows 95 the HyperTerminal program can be used.

 To test your MODEM, do the following:

  1. Start the terminal data program
  2. Enter the string ATZ
  3. Enter the Caller ID string to be tested
  4. If OK results, continue
  5. Have someone call you and watch the terminal screen
  6. If Caller ID is working, you will see the word RING, followed by one or more additional data lines. The word RING will then continue to appear for each incoming ring.
  7. If Caller ID is not working, you will only see the word RING for each incoming ring. If this is the case try another setup string and go back to step 2.

The most common result, when Caller ID data works, is the following:


DATE = xxxxx

TIME = xxxx

NMBR = xxxxxxxxx

NAME = xxxxxxxx



There are other formats as well. The key point is that other data generally appears between the first and second rings.

Some telephone companies, especially in Canada, ship Caller ID data in different formats. If you see a format different from the above, send us the data and information via E-Mail at

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