3Com VoIP gateway helps enterprises migrate to IP communications using an economical overlay strategy that aligns financial considerations with performance needs and lays the foundation for a successful deployment of Session Initiation Protocol (SIP)-based applications. The gateway enables interoperability between legacy equipment and applications including PBXs, the public switched telephone network (PSTN), analog phones and fax machines and a converged IP network. It provides all necessary functions and protocol support for handling voice calls between traditional circuit-switched phone networks and an IP network.