Patent ID: 7301661

Claim:
A communication terminal device comprising: an SIP call control unit which performs call control by using an SIP (Session Initiation Protocol); a recognition unit which recognizes that a calling has become an error according to a response signal sent back from a called party terminal after making the call according to the SIP call control procedure; a redial management unit which manages a redial interval to make a redial when the calling has become an error; and a redial control unit which performs redial control according to redial information when the calling has become an error and the response signal contains the redial information wherein: the redial management unit has a unit which stores a minimum value, a maximum value and a specified value related to the redial intervals, and the redial control unit has a unit for redialing by using the specified value when time information indicative of a time period after which an incoming call can be accepted, that is contained in the redial information of the reponse signal, has a value other than the redial interval between the minimum value and the maximum value or the redial information has an unanalyzable content.