On building an Internet telephony gateway

An Internet telephony gateway server is proposed to integrate the Internet into the public switched telephone network (PSTN) and allows speech communication to take place between users using conventional telephones. Each gateway is composed of a voice modem connected to the server computer and a set of server software. Audio signal is converted into digital form by the voice modem, then the digital bitstream is encoded and transmitted by the software over the Internet, a telephone connection is established and terminated with the local trunk line. During the process encoded voice data buffered and stored by a buffering mechanism. The operating system is Microsoft Windows 2000 and telephony application program interface (TAPI) is used to control the voice modem and the coupled trunk line. Since Internet is used as the transport medium between two communicating gateways, long distance phone charges is saved while the user still use the ordinary telephone as the end-point device instead of the headset and the personal computer (PC).