A telephone adapter for Internet telephony systems

In order to make the Internet telephony system a step closer to being a viable replacement of the conventional telephony system, an Internet telephone adapter (ITA) is proposed to interface a conventional telephone to the host computer. With the ITA, there is no longer the need for the current practice of using the host computer's microphone as the audio input and the internal or external speaker as the audio output to carry out a conversation. Users are able to dial an Internet telephone number to make a connection, be notified of an incoming Internet call through ringing of the telephone set, and carry out a conversation using the conventional telephone handset. This paper describes the design and development of an ITA which is connected to the parallel port of the host computer and optionally, to an existing sound card in the host computer. This will allow the ITA to be used as a stand-alone device or in conjunction with a sound card to support full-duplex real-time voice communication across the Internet. (C) 1997 Elsevier Science B.V.