Patent ID: 8190154

Claim:
A communication system comprising: a subscriber information storage device configured to store a plurality of subscriber information; a registration unit configured to register, in addition to a first subscriber information, a second subscriber information in the subscriber information storage device, as sub-registrant subscriber information of a first terminal unit, the first subscriber information being the subscriber information associated with the first terminal unit, and the second subscriber information being the subscriber information associated with a second terminal unit, wherein the registration unit registers, in addition to the second subscriber information, the first subscriber information in the subscriber information storage device, as sub-registrant holder subscriber information of the second terminal unit, a reception processor configured to acquire the sub-registrant subscriber information associated with the first subscriber information by referring to the subscriber information storage device, when transmission is made to the first terminal unit, and subsequently to perform processing of reception at the second terminal unit with use of the sub-registrant subscriber information, the reception processor acquires the sub-registrant holder subscriber information associated with the second subscriber information by referring to the subscriber information storage device, when transmission is made to the second terminal unit, and subsequently performs processing of reception at the first terminal unit with use of the sub-registrant holder subscriber information; and a transmission processor configured to acquire the sub-registrant subscriber information associated with the first subscriber information by referring to the subscriber information storage device, when transmission is made from the first terminal unit, and subsequently perform processing of transmission from the second terminal unit with use of the sub-registrant subscriber information.