ASHTALK:SOFTWARE ACHIEVING DELAY-FREE VOICE TRANSMISSION OVER A LOCAL AREA NETWORK.

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Description/Abstract

In many organisations users’ workstations are linked by a local area network of 10 megabits per second or more. The ASHTALK software system was conceived, designed and implemented to support an aural conversation over a local area network. The voice link is ‘delay-free’ i.e. the voice is heard 100-150 ms after speaking. This is equivalent to a conventional telephone link and much faster than existing Voice over Internet Protocol, VoIP, systems that impose typically 500-700 ms delay. ASHTALK achieves its efficiency by real-time programming techniques including polling instead of waiting for events, and a single thread execution to avoid overheads of multiple threads. ASHTALK is in C++ under Microsoft Windows so is portable. It multitasks and so allows the PC workstation to continue its other tasks such as word processing. ASHTALK is easy to install and a non-specialist can operate it. It contains an answer-phone function with facility to record voice traffic during the user’s absence. Extraneous data traffic on the network link leaves ASHTALK’s performance unaffected in terms of sound quality and delay. Continuing operation of the ASHTALK prototype at the University of Southampton indicate that it could replace the conventional telephone system on sites with a 100Mbps network.