Patent ID: 8331349

Claim:
A SIP telephone system to secure user's personal mobility, the system comprising a plurality of SIP telephone terminals, a switching device connected to the SIP telephone terminals via a communication network, and a SIP server connected to the communication network, wherein the SIP telephone system manages a log-in/log-out state at the plurality of SIP telephone terminals, and wherein: the switching device comprises a transfer section for transferring an incoming call with a destination of a first SIP telephone terminal, on which a user has logged in and in which a transfer function is set, to a second SIP telephone terminal at a transfer destination, and the SIP server comprises: an internal timer for counting time; and a releasing section, wherein: the releasing section releases the setting of the transfer function when the internal timer counts a first predetermined time after completion of the setting of the transfer function; the releasing section releases the setting of the transfer function when the internal timer counts a second predetermined time after termination of the incoming call at the second SIP telephone terminal; the releasing section releases the setting of the transfer function when the user logs in a second time on the first SIP telephone terminal or logs in on a third SIP telephone terminal other than the first and second SIP telephone terminals; and the releasing section releases the setting of the transfer function when a new transfer destination is set at a fourth SIP telephone terminal other than the first and second SIP telephone terminals, the new transfer destination being a destination other than the second and fourth SIP telephone terminals.