There are a number of technologies that allow both voice and data to be exchanged on a single phone call without having to hang up. By exploiting this capability, a variety of new applications can be constructed that make the everyday telephone call a richer experience.
The first of these technologies to be broadly available is VoiceView, which is an alternating voice and data protocol for hardware devices and software applications that optimizes the integration of voice and data communications. VoiceView allows a software application to very quickly switch back and forth between sending voice and sending data on a call.
Voice-aware applications benefit the user by using a computer to enhance communications during normal telephone calls. The power of the computer increases the amount and accuracy of exchanged information and decreases the time for a call. New types of interaction, which are not possible in either a standard data call or a standard voice call, also become available. Applications for Microsoft Windows incorporate these benefits of VoiceView and other voice-data technologies (such as simultaneous voice-data or ultimately ISDN) by using the File Transfer API and the Windows Sockets API.