Patent ID: 8630201

Claim:
A call control system comprising a call controller for performing a call control by selectively using a plurality of communication networks and a plurality of terminal devices, the call controller comprising: a receiving-side terminal device current state monitoring unit for acquiring from a terminal device on a receiving side available network data representing a communication network available to the terminal device on the receiving side; an available network data holding unit for holding the available network data acquired by the receiving-side terminal device current state monitoring unit; and a call control unit for, upon receipt of a reception request from the terminal device on the receiving side, concurrently transmitting call control signals each having a call identifier for identifying a call to the plurality of communication networks, respectively, estimated to be available to the terminal device on the receiving side, based upon the available network data held by the available network data holding unit, and for, upon receipt of each of call responses to the call control signals concurrently transmitted, from each of the plurality of communication networks, determining a communication network to be used by the terminal device on the receiving side based upon call control condition information representing a condition relating to the call control and communication resource information included in a single call response received in an order, each of the plurality of terminal devices comprising: a communication unit for communicating with the exterior; and a terminal-side call control unit for, when the communication unit receives the call control signals concurrently transmitted through the plurality of communication networks, respectively, estimated by the call controller to be available to the terminal device on the receiving side, returning a call response including the communication resource information together with the identifier through each of the plurality of communication networks to the call controller.