Patent ID: 7471673

Claim:
An IP telephone system, comprising: a first IP telephone exchange which manages a first IP telephone terminal; a second IP telephone exchange which manages a second IP telephone terminal; and a holding device which is call-connected with the second IP telephone terminal when the first IP telephone terminal holds a call connection with the second IP telephone terminal and call disconnected with the second IP telephone terminal when the call between the first and second terminals returned from hold state to connection state a call processing database which stores a telephone number, an IP address and connection state information at least for each of the IP telephone terminals; a subscriber information database which stores a telephone number, an IP address and connection state information at least for each of the IP telephone terminals; wherein, when the first IP telephone exchange receives an emergency call notification, the first IP telephone exchange transmits a setting change request to the call processing database and the subscriber information database, the call processing database change the connection state information to “emergency call”, and the subscriber information database change the connection state information to “emergency call”.