Abstract: A system to interworking a call between a plurality of networks having different formats. The system has a GR-303 system, an integrated services digital network system, a service platform, and an asynchronous transfer mode system. The system has a signaling processor that is adapted to receive the call signaling and to process the call signaling to select a connection to one of the GR-303 system, the integrated services digital network system, the service platform, or the asynchronous transfer mode system. The signaling processor thereby selects the corresponding system on the connection. The signaling processor transports a control message identifying the selected connection. An interworking unit receives the user communications and the control message. The interworking unit converts the user communications from the format in which it was received to the format that is compatible with the selected system. The user communications are then transported on the selected connection.