GLOSSARY OF TERMS

3-to-1 Rule - When using multiple microphones, the distance between microphones should be at least 3 times the distance from each microphone to its intended sound source.

A/B Roll - Videotape editing arrangement where scenes on tape are played alternately on two source recorders and recorded on a third recorder Typically, the final output recorded contains some scenes from the two sources with cuts, mixes and wipes between the scenes.

Aberrations - Certain aberrations degrade the image formed by a lens.

Absorption - The weakening of radio wave strength by losses in various materials.

AC (also ac) - Alternating Current

Accelerators - Specialized computers that speed up applications requiring large amounts of memory

Achromatic - Completely colorless white light

ACLE - Analog Component Link Equipment

ACTV - Advanced Compatible Television, advanced television transmission system; currently two such systems exist. ACTV1 is a channel/receiver compatible system with increased resolution ACTV2 is similar to ACTV1 but with improved audio and still more advanced resolution.

Adaptor (also adapter) - A device to permit interconnection of two connectors or devices that do not directly match

ADC (Analog-to-Digital Convener) - A digital electronic component that converts an electrical signal into discrete binary values.

Address - An exact location of information or data in a computer’s memory

ADTV - Advanced Definition Television

AECT - Association for Educational Communications Technology

AF - Audio frequencies, typically 20-20,000Hz.

AGC - Automatic Gain Control

AIM - High-end protocol for Ascend-to-Ascend calls; rich in features but no interoperability with other vendors.

ALC - Automatic Lever Control or Automatic Light Control

Algorithm - A set of calculations; normally a specific routine used by a programmer to complete a task

Aliasing - Jagged lines and rough edges that may appear with computer-generated images

All Call - A single control, which allows the operator to talk to all stations simultaneously while overriding all programming, as in an Electronic Learning Laboratory or central sound system.

AM - Amplitude Modulation. The system of radio transmission based on varying the amplitude of the power output while the frequency remains the same. Also see FM, FREQUENCY MODULATION

Ambient - In audio-visual, unwanted light or sound

American National Standards Institute (ANSI) -Organization responsible for most standards used for US audio-visual and computer equipment

Alphanumeric - An alphabetic or numeric character that car be entered from a standard keyboard. Does not include special “control characters”. See CONTROL CODE

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Ampere - A unit of electrical current equal to watts divided by volts, usually called amps

Amplifier - A device, which supplies power to and strengthens an incoming signal for output

Amplitude - The magnitude of a quantity or strength of a signal. In electronics, amplitude usually refers to either voltage or power

Analog - Represented as a continuous signal or quantity, continuous, as opposed to digital; represented by discrete numbers with an extremely wide range of values

Analog Gateway - A means of connecting dissimilar codecs. Incoming digital signal from one type of codec is decoded by a similar codec and converted to analog. The analog signal is then passed to the dissimilar codec, coded, and decoded at the far end. Analog gateways achieve interoperability in a non-standard environment, but have the disadvantages of degrading video and audio quality and often reducing functionality.

Analog Recording (Multi-Image Devices) - A method of recording control information (encoding) by a continuous but varying signal rather than discrete (digital) pulses

Analysis Motion Picture Projectors - Projectors that have the capability of moving film through at varying speeds so that the viewer can analyze the action or details of the image. Speeds range from normal to very slow 1 to 10 fps) and total stop action, so individual frames can be examined

Anamorphic - A type of lens adaptor designed to produce a wide screen image from an equally condensed image on the film

Anechoic - Headsets and headphones, neither having nor producing echoes (as in anechoic chamber)

Animation - Making still images appear to move on the screen, sometimes referred to as rendering

Annunciator - Visual or audible signal to get attention of student or instructor, as in an ELECTRONIC LEARNING LABORATORY.

ANSI - American National Standards Institute, the organization responsible for most standards used for US audio-visual and computer equipment

Antenna SpliIte. - A device for electrically matching a single antenna to multiple receivers.

Anti-Aliasing - Specific programming designed to reduce or eliminate the jagged edges and lines that sometimes  appear in computer-drawn images

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Aperture - Size of an opening: diameter of a lens in relation to its focal length. The size of the aperture is controlled by the iris adjustment.. By increasing the f-stop number less light is permitted to pass to the pickup device.

Append - Adding one file to another; when one file is appended to another, the size of the original file increases Architecture - The internal design of a computer system

ASC (Video) - Automatic Sensitivity Control; detects light intensity and keeps camera in optimum working condition as it applies to light input.

ASCII. - American Standard Code for Information Interchange; a standard method of encoding characters on computers, enabling computers to communicate data to other computers. The code uses 7 BITS to represent 128 letters, numbers, and characters

Asynchronous.  Lacking synchronization. In video, a signal is asynchronous when its timing differs from that of the system reference signal.

Aspect Ratio- The proportions of a projected picture area. In the US, standard video aspect ratio is 4 units wide by 3 units high, usually shown as 41

ATM (Asynchronous Transfer Mode) - A transporting and switching method in which information does not occur periodically with respect to some reference such as a frame pattern.

Attenuation - A decrease in signal voltage during its transmission from one point to another

ATV - Advance TV, including several versions of improved or higher-quality television, including -IDTV, IDTV, EDTV, and several other television systems considered better than the currently available and used systems. Some ATVs use compact disc sound quality

Audio Active (AA) - Type of Electronic Learning Laboratory in which a student can hear a master tape, respond into a microphone, and hear his or her response through headphones. Also referred to as Level II Lab.

Audio Active Compare (AAC) - Type of Electronic Learning Laboratory in which a student can hear a master tape, respond into a microphone, and have both sounds recorded on separate tape tracks for comparison. Also referred to as Level Ill

Audio Bridge - Also known as a mix-minus audio system. A device that mixes multiple audio inputs and feeds back composite audio to each station, minus that station’s input .

Audio Cassette - A cassette designed to hold audiotape for automatic play in tape recorder devices. See also COMPACT CASSETTE.

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Audio conferencing - Teleconferencing that employs voice communications, usually accomplished using standard telephone lines. When more than one person is in a single location, speakerphones or special audio conferencing terminal equipment is employed. When more than two services may be employed to improve the quality of the conference. (ITCA)

Audio Leads Video - Audio begins to cross-fade prior to a video switch. This can only occur with an audio mixer, not an audio switcher.

Audio Monitor - A speaker for listening to the playback of a tape or record, editing and quality check

Audio Passive (A or AP) - Type of Electronic Learning Laboratory in which a student can only listen to a master tape, usually through headphones. Also referred to as Level I

Audio Tape Recorder - See RECORDER

Audio Track - The portion of videotape, which carries the audio signal

Audio-In - Input jack that delivers a signal to a piece of equipment or a jack that receives a signal using a cable with the proper connectors

Audio-Out - Output jack, which brings an audio signal from a piece of equipment or one, which delivers an audio signal using a cable with the proper connectors

Autoprogramming- will automatically search and store all active channels into a TV’s memory.

Auto Stop - A device, which automatically stops or disengages the mechanism at the end of recording or playback. This feature may be combined with Automatic Shutoff. Full Auto Stop turns the mechanism to stop position at tape end in any mode including fast forward and rewind Auto-Boot - A process by which a computer automatically loads its operating system and runs a program upon power-up. See AUTOEXEC.BAT, BOOT

AutoExec.Bat - An MS-DOS file that is automatically executed when a computer is powered up- the file may contain commands to load and run other programs on the disk

Automatic Level Control (ALC) - A circuit used in audio and video recorders to control the level of the recorded signal automatically to provide uniform level without distortion due to overloading. Also called Automatic Gain Control AGC). An ALC Defeat control permits manual level control for wide ranges or special recording purposes

Automatic Program Transfer - Allows the program material in electronic learning laboratories to be transferred to all students by the use of one control at the operator position

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Automatic Shutoff - A device, which automatically turns the electronics off at the end of recording or playback. This feature may be combined with an Auto Stop mechanism

Axis - The X axis is a horizontal line across the center of the screen, the Y axis is a vertical line and the Z axis is in the third dimension, perpendicular to the X and Y axes and indicating depth and distance.

B

Backing - The material, usually Mylar, onto which audio and video data are recorded by means of altering an oxide coating

Back-up - A copy of computer data. Since computer files can be erased or damaged, it is always a good idea to keep a copy of them

Band - Circular recording area made up of tracks on storage devices such as magnetic discs, drums and tape loops

Bandwidth - The range of frequencies in a channel            

Boolean - A system of logic based on true/false comparisons

Bar Code Reader - Incorporating LEDs and photo diodes, this device reads information expressed in a combination of bars of varying width.

Barrel Distortion - The distortion of a scone, which occurs when a wide-angle lens is used: edges appear rounded and out of proportion with the center of the image

Bar Test Pattern .4 standard test pattern used to adjust a video monitor or receiver

BASIC -  ”Beginners All-purpose Symbolic Instruction Code”, a programming language supplied with many personal computers

Batch, Batch File   a file containing commands that would ordinarily be typed from the keyboard. When batch, or “.BAT” files, are executed, the computer treats them as though they had been entered from the keyboard. BATCH commands are executed sequentially

Baud. Baud Rate . The speed at which data is transmitted, roughly equivalent to bits per second

Beam - Flow of electrons

Beam Adjustment - Control on video cameras, which regulates the current in the beam

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Bearding - Video distortion that appears as short black lines extending to the right of bright objects within a scene

Beta - A W• video cassette format not compatible with the VHS format which is also Z” but differs electronically

Beta ED - YC signal processing (Camera/VCR/monitor), yields better resolution and less noise

Bezel - The frame around a television or monitor that hides a small amount of transmitted information, sometimes information not meant for viewing

Bias - A direct current (DC) or high frequency alternating current (AC) signal fed to a magnetic recording head with the audio in order to minimize distortion. AC Bias ordinarily provides higher fidelity but at higher cost

Bi-directional Microphone  A microphone that picks up equally from two opposite directions. The angle of best rejection is 90~ from the front (or rear) of the microphone, that is, directly at the sides.

Binary - The ‘base 2” numbering system. All numbers are formed by a combination of 0 and 1; the basic numbering system used in all digital electronic devices

Binder - Adhesive which binds iron oxide particles to a Mylar tape backing material, used in audio and videotapes

Bipolar - A signal containing both positive and negative amplitude. May also contain a zero amplitude state.

Bit - Binary digit, a 0 or 1: the smallest piece of information a computer understands. Eight bits form a BYTE

Bit Mapping - A method of graphic display, described in terms of pixels

Bitpad - An input device. See GRAPHICS TABLET

Bloom - Unacceptable TV picture caused by too much light

BNC Connector - A locking typo of industrial connector commonly used in professional video systems

BONDING - Bandwidth on Demand interoperability Group -A group of electronic equipment manufacturers formed to promote the use of inverse multiplexers through the development of an operational standard. I-muxes compliant with the same modes or levels) of the BONDING standard are now available from many manufacturers.

Boom - A camera, light or microphone mount on a long extension, usually to reach difficult places, often for high camera shots or for arranging for a microphone to he placed over a speaker’s head

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Boost - To raise or strengthen a signal

Boot - To start up a computer by loading it’s operating system; see also AUTO-BOOT

Boundary/surface Microphone - A microphone designed to be mounted on an acoustically reflective surface.

bps - bits per second

Braille Marks - Special raised markings on function controls which permit identification and operation by touch

Break - A command function that interrupts a computer process, which will often stop execution of a program. It can be given by pressing the CONTROL and break keys simultaneously on an IBM-PC. Many programs are designed so that the BREAK command will not disrupt execution, so data won’t be lost

BRI (Basic Rate Interface) - SON access consisting of two

“B” (Bearer) Channels of 64Kbps each, and one “D” (Data or control) Channel of 16Kbps.

Bridge - An electronic device which mixes the signals from three or more locations e.g. for audio or audio graphic teleconferencing.

Brightness - Achromatic intensity, relative lighting without regard to color; light emitted from a surface such as a screen is measured in FOOTLAMBERTS, FOOTCANDLES, or LUX

Brightness Ratio - The difference between the brightest (whitest) and darkest (blackest) areas in an image. The wider the brightness ratio the wider the contrast ratio

Broadband - A circuit, which can operate over a wide range of frequencies. Cable TV is an example

Buffer - An area of memory used to store information temporarily. In graphics, part or all of a screen image may be stored in a buffer

Bug - An error in a computer program, which causes unexpected or unintended results

Burn - Extra bright images, which remain on the surface of a camera tube as a ghost image when other images are being shown

Byte - An 8-bit storage unit, equivalent to one character. For example, the bits: 01000001 represent the letter “A’

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