Download the AT commands pdf sheet commands for the modem you are using.... connect the modem to hyperterminal and type the command on the terminal window and see the response of the modem on the hyperterminal window.... before doing this check the modem baud rate and set the same settings for the COM port properties in the hyperterminal....... search the forum , it has lots and lots of material which many of them have put and many have answered these querries.........