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Modem diagnostics

Updated: January 21, 2005

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Modem diagnostics

You can verify that your modem is working properly by using the diagnostics that are available through the Phone and Modem Options icon in Control Panel. (For more information on this procedure, see Test a modem.)

When you query a modem, Windows tries the following commands and displays the results.


Command Response


Initializes the query.


Model identification (ITU V.250 recommendation is not supported by all modems).


Fax classes supported by the modem, if any.


Shows whether the modem supports the Rockwell voice command set.


Displays manufacturer's information for n = 1 through 7. This provides information such as the port speed, the result of a checksum test, and the model information. Check the manufacturer's documentation for the expected results.


Displays the current selected country/region.


Displays all countries/regions supported by this modem.

You can also record a log of commands as they are sent to the modem by communication programs or the operating system. For more information, see Log and view modem commands.

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