Glossary of Videoconferencing Terms & Links
This list contains information relative to the planning information that educators will need as they move ahead to implement educational videoconferencing programs.
Technical Terms
Bandwidth - The transmission capacity of an electronic medium, such as network wiring, fiberoptic cable, or microwave links; also the range of signal frequencies where a piece of audio or video gear can operate, or the difference between high and low limiting frequencies.
Bridge (see also router) - a networking device that connects several video sites into one videoconference. It can route multiple protocols, such as TCP/IP and XNS, while bridging other traffic.
CODEC - Coder - Decoder. This may be either a software-only, or a hardware assisted scheme that is used to process digital video and/or audio files. The amount of data required to represent moving pictures with sound is reduced by a CODEC, which normally discards redundant data on compression. Some of the more widely used CODECs are Indeo, MPEG, and CinePak.
Compression - The conversion of digital data, typically video and audio, into a more compact form by using complicated algorithms. The data is decompressed at the receiving end.
Decoder (see also CODEC)- A hardware or software system that translates data streams into video or audio information.
Decompression (see compression)
Desktop Video (see also room-size video) - This system is based on a desktop computer on which a small camera is mounted on top of the monitor. Software to allow image display, voice transmission, and other functions of the system resides in the computer. These systems are designed for one-on-one interaction, but can accommodate two or three people on each station if necessary. Desktop systems also include software for sharing control of programs, documents and other files, and are designed to facilitate collaboration.
Distance Education (see distance learning)
Distance Learning - Educational instruction carried out at a site other than the classroom where an instructor is located, typically via satellite or cable television and in real time.
ELMO - Electric Light Machine Organization, maker of visual presenters for teleconferencing and distance learning applications; the camera used to send document images over videoconferencing systems to remote sites.
Interface - A device that connects two pieces of hardware, such as the link between a computer processor and peripherals. Also, the means by which a computer user gives instructions and receives information from a computer.
ISDN - Integrated Services Digital Network; an international digital telecommunications standard that accommodates voice, data, and signaling and brings high bandwidth to the microcomputer desktop.
Multiplexing - sending more than one modulated signal within a bandwidth, permitting better use of the carrier signal bandwidth. More than one simple signal can thus be transmitted as part of a single complex signal and separated out at the receiving end.
Room-Size Video (see also desktop video) - This system is also based on a microcomputer, with the video display projected through one or two large (27" or larger) monitors, or through a digital video projector for screen or wall display. These systems are designed for visibility and interaction of larger groups of people, such as a classroom of 30 students or a meeting of 12 people. Often, such a system includes microphones set in the middle of a table designed to pick up voices from anywhere around the table. In a classroom setting, demonstration and presentation tools, such as overhead projectors and electronic blackboards are used to support typical instructional settings, and may include a microphone for each participating student.Router (see also bridge) - A protocol-dependent device that connects networks. It is useful in breaking down a large network into smaller subnetworks. Routers introduce longer delays and have lower throughput rates than bridges. Like a bridge, a router restricts local area network (LAN) traffic.
Standards
H.320 Narrow-band Visual Telephone Systems and Terminal Equipment This is a popular videoconferencing standard in use today. It requires a digital network to provide the electronic transportation path between the videoconferencing endpoints. ISDN is the transport mechanism used most often with H.320 systems.
H.323 runs over Local Area Networks (LAN's). H.320 and H.323 use many of the same protocols and both support H.261 and H.263 video algorithms. H.323 is the standard for visual telephone systems and equipment for local area networks (LAN's) that provide an unguaranteed quality of service (QOS).
T1 (also T-1) - A digital transmission link that can pass data at a rate of 1.544 megabits per second over normal twisted-pair wiring. It can handle 24 voice channels at 64 kilobytes per second and is a North American telecommunications standard.
Videoconference - A conference during which participants at two or more locations are linked by fast telecommunication lines and are able to see and hear one another in real time.
back to topTechnical & Other Term Links
Large and more extensive lists and descriptions of technical terms and information related to the instructional and other use of videoconferencing will be found at these external sites.
Intel Corporation: follow the links to information about products, protocols, terms, and some "how-to" information.
http://www.intel.comPacific Bell: this site has a wealth of information for technical interests and for instructional support.
http://www.kn.pacbell.com/wired/vidconf/U.S. Federal Government Standards and Terms: this site provides standards information in videoconferencing for the nation, as well as information about telecommunications in general.
http://ntia.its.bldrdoc.gov/fs-1037/