Patent ID: 8208411

Claim:
A telephone system which includes an IP (Internet Protocol) phone, an IP proxy response phone, and a server for controlling reception/transmission between the IP phone and the IP proxy response phone, wherein said server determines a state of the IP phone upon receiving an incoming call addressed to the IP phone; when it is determined that the IP phone is unable to answer the call, said server applies an identifier of the IP phone to transfer the incoming call to the IP proxy response phone; wherein the identifier is a History-Info header or a User-Agent header of an INVITE message; wherein upon receiving the incoming call, the IP proxy response phone determines whether the incoming call has been transferred or is addressed to the IP proxy response phone; wherein the IP proxy response phone correlatively stores a caller number and a callee number of the IP phone in a case where the INVITE message includes the History-Info header or the User-Agent header; and wherein the IP proxy response phone correlatively stores a caller number and a callee number of the IP proxy response phone in a case where the INVITE message does not include the History-Info header or the User-Agent header.