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Glossary of Terms
ADC (Analog-to-Digital Conversion)
Process of converting analog signals to a digital representation. DAC represents the reverse translation.
Algorithm
Any step-by-step problem-solving procedure. Transmission of compressed video over a communications network requires sophisticated compression algorithms. Some videoconferencing systems offer both proprietary and standard compression algorithms.
Analog Signal
A type of signal that encodes voice, video, or data transmitted over wire or through the air, and is commonly represented as an oscillating wave. An analog signal can take any value in a range and changes smoothly between values, as opposed to digital signals, which is characterized by discrete bits of information in numerical steps. An analog signal can transmit analog or digital data.
Application Sharing
Application sharing is a feature that allows two or more videoconference sites to view and work together on a document, presentation, website or application. One site launches the application and shares it with the other site(s).
Asynchronous Transmission
A mode in which the sending and receiving serial hosts know where a character begins and ends because each byte is framed with additional bits, called a start bit and a stop bit. A start bit indicates the beginning of a new character; it is always 0 (zero). A stop bit marks the end of the character. The time interval between characters may be of varying lengths. Synchronous data uses an external reference clock to unify both ends of the data circuit. (Compare with Synchronization).
ATM (Asynchronous Transfer Mode)
A high bandwidth, high speed (up to 155 Mbps), controlled-delay fixed-size packet switching and transmission system integrating multiple data types (voice, video, and data). Uses fixed-size packets also known as "cells" (ATM is often referred to as "cell relay").
Audio
In video communications, electrical signals that carry sounds. The term is also used to describe systems concerned with sound recording and transmission, such as speech pickup systems, transmission links that carry sounds and amplifiers etc.
Audio Bridge
Equipment that mixes multiple audio inputs and feeds back composite audio to each station after removing the individual station's input. This equipment may also be called a mix-minus audio system.
Audio Conferencing
Voice only connection of two or more people using standard telephone or speakerphones. Audio bridges may link multiple sites.
Autonomous System
Internet (TCP/IP) terminology for a collection of gateways (routers) that fall under one administrative entity and cooperate using a common Interior Gateway Protocol (IGP).