INTERCOM SYSTEM

PROBLEM TO BE SOLVED: To provide a convenient intercom system for confirming a transfer from an intercom slave unit before answering by a portable telephone set.SOLUTION: When a call is received from the slave set 2, a transfer device 3 transmits a call event notification message to the portable telephone set 5 through an event management server 40. Thus, the intercom system becomes convenient, since a user can confirm the transfer from the slave set before answering by the portable telephone set. Further, when the user performs answering by the portable telephone set 5, the transfer device 3 only calls the call control server 41 and does not receive a call from the call control server 41 or the portable telephone set 5. Thus, there is no need of allocating a dedicated telephone number (a subscriber number) to the transfer device 3, so that a maintenance cost can be suppressed.