Device and method for cleaning telephone number list

Claim 1

A cleaning system for a telephone number list including a computer such as a personal computer, comprising the following elements of: being connected with an ISDN to process circuit-switched call control procedures defined in the ITU-T recommendation Q.931 as a calling terminal; retrieving a telephone number sequentially from a telephone number list to be cleaned as a called party number to send a SETUP message including an unrestricted or a restricted digital information in a bearer capability information element to the network; sending a DISCONNECT message to the network immediately to perform a clear sequence and determining the called party number in the SETUP message effective when the network receives the SETUP message sent and transfers an ALERTING or CONNECT message; performing a clear sequence immediately and obtaining a cause in an information element of the DISCONNECT message from the network to determine the called party number in the SETUP message either effective or null according to the cause when the network does not receive the SETUP message sent and transfers a DISCONNECT message; and generating a new telephone number list, which includes the telephone numbers determined effective and the telephone numbers determined null, separately.