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Glossary

Bandwidth – A measure of the capacity of a communications channel. The higher a channel’s bandwidth, the more information it can carry. Example: T1 has a greater bandwidth than ISDN.

Codec – a hardware circuit that converts analog video or audio signals into digital code and vice versa. A codec is short for COder-DECoder.

Compressed Video – a method currently used to transmit images electronically. Compression of sequences of images is necessary because of the huge volume of digital information inherent in video. Example: A CD-ROM with a memory capacity of about 650 megabytes can store only 30 seconds of a video segment without video compression. With compression, an approximately 70 minute-long video program can be stored.

Desktop Videoconferencing – Videoconferencing on a personal computer.

Dialable – A line that can be dialed much like a telephone to any other site that has compatible equipment. Contrast to fixed connections, which always connect to the same two points.

Distance Education – The process of providing instruction when students and instructions are separated by physical distance.

ELMO Visual Presenter – Consists of a camera mounted on an extension arm and a stage on which to place graphics, printed materials, or small objects. The item placed on the ELMO can be seen on the monitor at each site.

HTML – Hypertext Markup Language. Coding used to publish documents on the WorldWide Web that allows links to information in files an any computer connected to the Internet.

ISDN – Integrated Services Digital Network. ISDN is a dialable, digital service available to most residences and businesses that offers much higher bandwidth than POTS (plain old telephone service).

JPEG – Joint Photographic Experts Group. A standard format for compression of images. Images on web pages are commonly stored in the JPEG or GIF formats.

Satellite conference – A conference between different locations where the communication links are made between orbiting satellites and various points on Earth. Communications satellites provide telephone, television, and data services between widely separated locations. The technique involves the transmission of signals from an Earth station to satellite. The satellite has equipment signals, amplifies them, and transmits them to Earth. Receiving stations then pick up the signals and provide the communications link.

Streaming – Playing video or sound in real time as it is downloaded over the Internet. Data is decompressed and played (by use of a web browser plug-in) as it is transferred to your computer over the World Wide Web. Streaming requires a powerful computer and fast connection since the file is not stored on your computer.

T-1 – High speed digital data channel that is a high-volume carrier of voice and/or data. Often used for compressed video teleconferencing. T-1 has 24 voice channels.

T-3 – A digital channel which communicates at a significantly faster rate than T-1.

Transponder – The part of a communications satellite that receives transmission from the ground (an uplink site) and retransmits it back to earth (a downlink site).

URL – Uniform Resource Locator. An address on the World Wide Web.

Videoconference – A video communications session between two or more remote locations, with live, animated image transmission and display.

Web Chat – A system that allows two or more logged-in users to set up a typed, real-time, on-line conversation across the World Wide Web.

References

D. Hardy, D. Fuddell, 1998, Distance Education: A Primer, University of Texas, Glossary, 1-9