See Chapter 3 on Media Encoding and Compression for a further discussion of compression schemes. 1.2.2.2 Audio as a Communication Channel Because bidirectional audio has often conjured up images of telephones, some of the early work on audio integration reflects this influence. This has been achieved through use of ISDN signalling, as well as through computer controlled telephones. ACM Conference on Multimedia, pp.373-382, Aug 1993. These devices offer an extremely low bandwidth for communication, and subsequently the interface does not afford rich delivery of information content.
Telephones are ubiquitous and cellular services offer mobility.
However, telephones primarily operate on a synchronous model of communication, requiring availability of both parties. A key aspect of the system was easy interruptability by the user during speech only interaction. A nomadic computing environment was developed at the Speech Interface Group to provide remote access to a set of desktop applications via telephony. Users hear messages and feedback via synthetic speech and audio playback. The Telephone as a Computer Terminal .