algorithm

A 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 signals

Audio/video signals currently used in broadcasting where the signal is represented by variable measurable physical quantities (such as voltage). Current TV and radio signals are analog, as are many telephone lines. (Contrast with digital)

audio

In video communications, electrical signals that carry sounds. The term is also used to describe systems concerned with sound with recording and transmission; speech pickup systems, transmission links that carry sounds, amplifiers and the like.

bandwidth

In casual use, the amount of information that can be transmitted in an information channel. High bandwidth Internet access means those web graphics load quickly on Netscape. High bandwidth videoconferencing means that the picture and sound will be clear.
In computers, the speed at which data can be transmitted on a communications frequency.
In telecommunications, the maximum frequency (spectrum) measured in Hertz or cycles per second, between the two limiting frequencies of a channel.

bit

binary digit. The smallest unit of information with 2 possible states. 1 or 0, yes or no, on or off.

bps

bits per second (lower case is significant)

bridge

In videoconferencing vernacular, a bridge connects three or more conference sites so that they can simultaneously pass data, voice, or video. Videoconferencing bridges are often called MCU's - multipoint conferencing units

broadband

A high-capacity communications circuit/path. It usually implies a speed greater than 1.544Mbps. (Contrast with wideband and narrowband)

BRI - Basic Rate Interface (ISDN)

3 digital signals over a single pair of copper wires: 2 voice (B) channels and 1 signal (D) channel. (e.g. voice and fax on a single pair of wires)

camera presets

Allows pre-defined camera angles to be programmed into a video conferencing system.

codec

Coder-Decoder. Video conferencing hardware that codes the outgoing video and audio signals and decodes the incoming signals. Prior to transmission, the codec converts analog signals to digital signals and compresses the digital signals. Incoming audio and video must be decompressed and converted from digital to analog and back.

Compression

Compression is a technique that reduces the quantity of bandwidth or bits required to encode a block of information so that it occupies less space on a transmission channel or storage device and a fundamental concept of video communications.

compressed video

When the vast amount of information in a normal tv transmission is squeezed into a fraction of its former bandwidth by a codec, the resulting compressed video can be transmitted more economically over a smaller carrier. Some information is sacrificed in the process, which may result in diminished picture and sound quality.

delay

The time it takes for a signal to go from the sending station through the video conference to the receiving station. This transmission delay for a single hop video conference connection is very close to one-quarter

desktop videoconferencing

Videoconferencing on a personal computer. Most appropriate for small groups or individuals (compare with room-based video conferencing). Many desktop videoconferencing systems support document sharing.

digital signals

Audio/video signals represented by discrete variations (in voltage, frequency, amplitude, location, etc.). A digital clock, for example, displays the time as discrete numeric values rather than angular displacement of analog hands. In general, digital signals can be transmitted faster and more accurately than analog signals. As an example, music from digital cd's is usually more clear than music from analog records. (Contrast with analog signals.)

distance learning

The incorporation of video and audio technologies so that students can "attend" classes and training sessions that are being presented at a remote location. Distance learning systems are usually interactive and are becoming a highly-valuable tool in the delivery of training and education to widely-dispersed students or in instances where the instructor cannot travel to the student's site.

document sharing

A feature supported by many desktop video conferencing systems that allows participants at both ends of a video conference to view and edit the same computer document

earth station

The term used to describe the combination or antenna, low-noise amplifier (LNA), down-converter, and receiver electronics used to receive a signal transmitted by a video conference.

echo-cancellation

Process of eliminating acoustic echo in a videoconferencing room.

echo effect

A time-delayed electronic reflection of a speaker's voice. This is largely eliminated by modern digital echo cancellation.

FCIF/QCIF

Standards-based formats for communicating between video conferencing systems from different vendors. QCIF is one quarter of the resolution of FCIF

frame rate

Frequency in which video frames are displayed on a monitor, typically described in frames-per-second (fps). Higher frame rates improve the appearance of video motion. Broadcast TV (full motion video) is 30 frames-per-second.

full duplex audio

2-way audio simultaneously transmitted and received without any interference or "clipping." A common feature of room-based videoconferencing systems. Contrast with half duplex audio.

full motion video

Full motion video is equivalent to broadcast television video with a frame rate of 30 fps. Images are sent in real time and motion is continuous.

Gateways are points of entrance to and exit from a communications network. Viewed as a physical entity, a gateway is that node that translates between two otherwise incompatible networks or network segments.

H.320 standard

A widely-used video compression standard that allows a wide variety of videoconferencing systems to communicate.

half duplex audio

2-way audio transmitted and received in turn (rather than simultaneously) so only one site can speak at a time. Contrast with full duplex audio.

IP

Internet Protocol

IP Address

An address that uniquely identifies each host on a network or Internet.
An IP address has a length of 32 bits, and is divided into four 8-bit parts, each separated by a period, as in 149.122.3.30. This kind of notation is called dotted decimal notation. Each part can consist of a number between 1 and 255.
In addition to an IP address, you can use a symbolic (domain) name provided by Domain Name Services (DNS) to designate an Internet address.

ISDN

Stands for Integrated Services Digital Network. ISDN is essentially a digital network that will provide seamless communications of voice, video, and text between individual desktop videoconferencing systems and group videoconferencing systems. ISDN is expected to replace current telephone lines.

LAN

Local Area Network  A network that interconnects devices over a geographically small area, typically in one building or a part of a building. The most popular LAN type is Ethernet. LAN's allow the sharing of resources and the exchange of both video and data.

Mbps

Megabits per second

multipoint video conference

Video conference with more than two sites. The sites must connect via a video bridge. (Compare with point-to-point video conference.)

narrowband

A low-capacity communications circuit/path. It usually implies a speed of 56Kbps or less. (Contrast with wideband and broadband)

Network

A group of stations (computers, telephones, or other devices) connected by communications facilities for exchanging information. Connection can be permanent, via cable, or temporary, through telephone or other communications links. The transmission medium can be physical (i.e. fiber optic cable) or wireless (i.e. satellite).

NTSC

Standard for scanning television signals. Used in the U.S., Canada, and Japan.

PAL

Standard for scanning television signals. Used in most European countries.

point-to-point video conference

Video conference between two sites. (Compare with multipoint video conference.)

proprietary compression algorithm

A vendor-specific algorithm for compression of a video signal. A videoconferencing system using a proprietary algorithm can only communicate with a remote site using the same algorithm. Many vendors also adhere to standard compression algorithms to facilitate communication across platforms.

public room

Video conferencing service offered to the public on a fee-for-usage basis.

room-based video conferencing

Video conferencing using a sophisticated system. Appropriate for large groups (compare to desktop video conferencing).

An algorithm convention for compression of a video signal. Adherence to standards allows communication among a wide variety of video conferencing systems, though not with the same clarity as two similar systems using a proprietary algorithm. H.320 is the most widely accepted standard in use today

T1

In North America, T1 service delivers 1.544 Mbps, whereas ISDN service delivers 128 kbps. The data travels over the line at the same speed, but for T1 lines, the capacity is twelve times that of ISDN. Typically channelized into 24 DS0s, each capable of carrying a single voice conversation or data stream. The European T1 or E1 transmission rate is 2.048 million bits per second.

T3

DS-3 In North America, a digital channel which communicates at 45 Mbps, or 28 T1 lines.

Telecommuter

A work-at-home computer user who connects to the corporate LAN backbone using remote access technologies.

Uplink

The earth station used to transmit signals for a satellite video conference.

Video bridge

Computerized switching system which allows multipoint video conferencing.

Communication across long distances with video and audio contact that may also include graphics and data exchange.

wide band

A medium-capacity communications circuit/path. It usually implies a speed from 64Kbps to 1.544Mbps. (Contrast with broadband and narrowband)