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Glossary of Terms

Glossary of Terms

A/D
Acronym for analog-to-digital converter. A circuit that converts analog values to digital values. Also Extron's product designation for Analog Distribution Amplifier
AC
Acronym for Alternating Current.
AC Coupling
A type of signal transmission circuit that block the DC component of a signal but uses the dynamic ( AC) component. Useful for observing an AC signal that rides on a DC signal.
Access
To retrieve information from a storage medium, such as videodisc, videotape, computer disk or tape, or videotape.
Access Time
The total time required to locate, retrieve, and display data after a retrieval command is given.
Active Addressing
A process which uses a complex numerical algorithm (a set of mathematical relationships) to generate signals that control all imagesels simultaneously.
Active Matrix
An LCD technology that uses a transistorized storage element (Thin Film Transistor) in each image cell to achieve precise control of the voltage applied. Active-matrix LCD projection panels have response times which allow viewing of animation, rapid mouse movement, and live-action video.
Adapter
The shared component in a system that handles host interface and communication connection functions. Also an interface between two sources.
Additive Color Process (RGB)
A color generation process used in video that combines Red, Green and Blue to make all colors. All three colors (red, green and blue) at 100% present a white image on a video screen. The absence of all three colors presents a black image. See Subtractive Color (CYMK).
Address
A notation (usually alphanumeric or numeric) that identifies a location of stored data in a storage device. Also a frame number or time code that identifies the location of video and/or audio data on tape or disc. To manage the storage of data, e.g., "That buffer can address 4 megabytes."
Address Mask
A bit mask used to select bits from an Internet address for sub-net addressing. The mask is 32 bits long and selects the network portion of the Internet address and one more bits of the local portion. Sometimes called subnet mask.
AGC
Acronym for Automatic Gain Control.
AGW
Acronym for American Wire Gage.
Aliasing
Jagged edges in text and also along the outer boundaries of diagonal or curved objects. Anti-aliasing refers to software adjustments that correct this effect. Caused by inadequate sampling techniques in computer-produced images. Basically, a false representation of a signal because of insufficient sampling of high frequencies or fast transitions, typically caused by lack of sufficient memory.
Alternating Current (AC)
A flow of electricity which reaches maximum in one direction, decreases to zero, then reverses itself and reaches maximum in the opposite direction. The cycle is repeated continuously. The number of cycles per second is the frequency. The average value of voltage during any cycle is zero.
American National Standards Institute (ANSI)
A science organization that sets measurement standards. For example, ANSI Lumens represents a brightness measurement made using ANSI methods. ANSI developed three-character lamp codes to identify lamps that meet particular application requirements, e.g., ENX.
American Standard Code for Information Interchange (ASCII)
The standard, eight-bit data character code-system that is used internationally to transfer information through the use of binary values between data processing systems. It is the most commonly used format for PC files. The standard code consisting of 7-bit coded characters (8 bits including parity check), utilized to exchange information between data processing systems, data communication systems, and associated equipment. The ASCII set contains control characters and graphic characters.
American Wire Gage (AWG)
A measure of the diameter of an electrical conductor. The larger the gauge number, the smaller the conductor diameter.
Amorphous
Refers to the atomic structure of silicon of which TFTs (thin film transistors) are made. Without definite form or shape and not crystallized. In the context of solids, the molecules are randomly arranged as in glass, rather than periodically arranged, as in a crystalline material.
Amperes (Amps)
A unit of measurement for electrical current.
Amplitude
The measured magnitude of an amount or strength of a signal. In electronics, amplitude usually refers to either voltage or power.
Analog
A continuous signal that takes time to make a transition from one level to another. Standard audio and video signals are analog. An analog signal has an infinite number of levels between its highest and lowest value. Analog signals cannot consistently and accurately be represented digitally.
Analog-To-Digital Converter (A/D)
A device used to convert analog signals to digital signals. A digital electronic component that converts an electrical signal (analog) into discrete binary values (ones and zeros).
Analog Video
A continuous-scale electrical signal carrying images and sounds. The use of physical variables such as voltage or current to represent numerical values.
Andora
An NTSC/PAL to VGA Converter with a built-in scan-doubler.
ANSI
Acronym for American National Standards Institute.
API
Acronym for Application Program Interface.
Applet
A short program written in Java that is attached to a World Wide Web page and executed by the visitor's browser.
AppleTalk
A networking protocol developed by Apple Computer for communication between Apple computer brand products and other companies' computers. This protocol is independent of what network it is layered on so it is "cross-platform or platform independent".
Application
The specific use of a technology to accomplish a task. Often used when referring to software programs that perform a specific task, such as word processing, database management, or graphics.
Application Program Interface (API)
A set of calling conventions defining how a service is invoked through a software package.
Application Sharing
Application sharing is a feature that allows two people to work together when one of the individuals doesn't have the same application, or the same version of the application. In application sharing, one user launches the application and it runs simultaneously. Both users can input information and otherwise control the application using the keyboard and mouse. Although it appears that the application is running on two PCs, it actually runs on only one while each user operates as though the application were running on both PCs. Files associated with the application can be easily transferred, so the results of the collaboration are available to both users immediately. The person who launched the application can lock out the other person from making changes, so the locked-out person sees the application running but cannot control it.
Applications Specific Integrated Circuit (ASIC)
Usually a fairly large IC that has been designed for a particular specialized electronic function. These are often used to take advantage of the right reliability and repeatability, low power consumption, small size, high speed, and very low cost associated with modern IC manufacturing capabilities.
ASCII
Acronym for American Standard Code for Information Interchange. Pronounced "ask-ee".
ASIC
Acronym for Applications Specific Integrated Circuit.
Aspect Ratio
The ratio of width to height of a frame or screen. The most common aspect ratios for projectors are 4:3, 5:4 and 16:9.
Asynchronous Transfer Mode (ATM)
A high-speed (up to 155 Mbps), high-bandwidth, low-delay, transport technology that can integrate multiple data types (voice, video, and data). ITU has selected ATM as the basis for the future broadband network because of its flexibility and suitability for both transmission and switching. May be used in the phone and computer networks of the future.
ATA
Acronym for Air Transport Association. The ATA adopts and maintains content protection standards for luggage that can be carried aboard commercial jetliners. InFocus offers a full line of carry cases (known as ATA cases) that meet or exceed ATA standards.
ATM
Acronym for Asynchronous Transfer Mode.
ATSC
Acronym for Advanced Television Systems Committee. A group formed in 1998 to explore the development of television systems for the U.S. more advanced than the existing NTSC system. Its work resulted in the DTV system adopted in 1996, which incorporates SDTV and HDTV components.
Attenuation
The decrease in the magnitude of a signal. A decrease in signal voltage during its transmission from one point to another.
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 Follow
A term used when audio signals are tied to other signals, such as video, and they are switched together. (The opposite of Breakaway.)
Audio Track
The section of a videodisk or tape that contains a sound signal. A system with two audio tracks can utilize either two independent sound tracks or stereo sound.
Audio Visual Authoring Language
A high-level, usually English-like computer programming language specifically designed to implement computer-based training (CBT) or interactive multimedia applications. Authoring languages allow users without formal training in programming to perform the programming functions of multimedia development.
Audio Visual Connection
The desktop system used on an IBM PS/2 that allows users to integrate text, sound, pictures and motion video into multimedia applications.
Author
The person who creates an interactive videodisc or multimedia program using an authoring language or system. Development a multimedia or computer program using an authoring language and/or authoring system. Authoring is a structured approach involving the development of all of the elements of a multimedia program or presentation.
Authoring System
A collection of specialized authoring programs that helps users without programming training design multimedia programs in a relatively "easy-to-learn" language or code.
Auto-sizing
Automatic picture sizing adjustment to compensate for different display modes, than enabling the display system to center the picture and fill the screen.
Auto-Termination
In equipment having loop-through or "daisy-chain" connections, termination is done at the last device on the chain. Some such devices provide termination automatically by the fact that there is no cable going out. Thus this is the last device and termination is provided.
Automatic Convergence
The automatic alignment of the convergence or red, green and blue color images on a CRT projector. These systems use the adjustment of green as the reference.
Automatic Gain Control (AGC)
A circuit that adjusts signal amplification based on feedback from its output or from another circuit. Automatic gain can be applied ahead of almost any circuit that requires specific levels to operate. As an example, the color decoder needs to see a particular level of color sub-carrier at its input in order to display the correct color at the output. There is a reference burst at the beginning of each horizontal line of known original amplitude. The AGC circuit looks at the incoming signal level and applies any gain correction necessary to make the burst amplitude correct. In the process of doing that, it also corrects the amplitude of the color information in the active picture area.
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).
AVA
Acronym for Audio Visual Authoring language.
AVC
Acronym for Audio Visual Connection.
Average Picture Level (APL)
The average signal level with respect to blanking during the active picture time. APL is expressed as a percentage of the difference between the blanking and reference white levels.
AWG
Acronym for American Wire Gauge.
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