Glossary of Terms and acronyms

VDSL:
Very high data rate Digital Subscriber Line. A simpler version of ADSL which allows for downstream transmission rates of up to 52.8 MBit/s but which can only be carried on standard telephone lines up to 4,800 feet from a telephone exchange.

Videoconferencing:
A closed user group interactive service used as a substitute for face to face meetings. Typically involves filming at one site and sending the signal to another with an audio circuit for the return loop. However, videoconferencing is now increasingly using the PC as a multimedia videoconferencing tool integrating data, voice and video. Such videoconferences may be spread across more than two sites.

Video On Demand (VoD):
Description of a service where a consumer can watch a particular video programme anytime he/she wants. To offer such a service broadband switched networks are essential.

VSAT:
Very small aperture terminal. Refers to small earth stations, usually in the 1.2 to 2.4 meter range and used primarily for closed user group business telecommunications networks. Such networks can either be one way (i.e. broadcast networks for data) or two way where they can support a variety of services ranging from data and file transfer, videoconferencing and voice traffic. The essential feature of 2-way networks is that they usually use a central hub for switching purposes. Such technology could be superseded by satellite on-board processingError! Bookmark not defined.. Small aperture terminals under 0.5 meters are sometimes referred to Ultra Small Aperture Terminals (USAT's).