Abstract: A source communication system and destination communication system communicate over an IP packet-switched data network through a pair of interface devices and gateways. In operation, a wireless source telephone converts voice signals to voice data packets in a specified format. The voice data packets are routed through a source switching device to a source interface device. The source interface device reformats the voice data packets to a format compatible with the communications protocol used by the IP packet-switched data network. A source gateway receives the reformatted voice data packets and routes the reformatted voice data packets over the IP packet-switched network to a destination gateway. The destination gateway routes the reformatted voice data packet to a destination interface device which, in turn, reformats the reformatted voice data packets to the specified format and outputs the re-reformatted voice data packets to the destination system.