D

DA - Display Adaptor

DAC - Digital-to-Analog Converter

DAT - Digital Audio Tape

Data - Any information stored or used by a computer. It often refers to files, separate from program files, which contain user supplied information, documents, graphics images, etc.

Data Base - A collection of related data stored in a logical structure which can be accessed by one or more computer programs

Data Compression - The reduction of the number of bits required to represent data through application of compression algorithms (e.g. by codecs).

DAW - Digital Audio Workstation

dB - Decibel, a measurement of sound

dBm - dB rating which indicates the number of decibels a signal is higher or lower than 1mw

DBS - Direct Broadcast Satellite, a satellite distribution system whereby signals are transmitted directly from an operational satellite to standard receivers: most effective distribution system for rural and remote areas, although transmission may be affected by weather

DC - Direct current, maintains a steady flow and does not reverse directions (as in alternating current); usually provided by battery power

DCE (Data Circuit-Terminating Equipment) - Equipment at a node or access point of a network. In RS-232C, the modem is DCE while the user device is DTE.

Dead - Very sound-absorbent, I.e. sound studios Debug - The process by which one examines end removes errors from software and hardware. See BUG

Decibel (dB) - A relative comparison of two signal amplitudes in a manner which roughly corresponds to human sensory response to the signals. In audio work, 0 dB is the threshold of hearing and 120 dB is the threshold of pain. A change of 3 dB doubles or halves the apparent loudness

Decoder - The device in a Synchronizer or Programmer which reads the encoded signal or pulse and turns it into some form of control. Compare with ENCODER

Decryptor - A descrambler or decoder designed to restore a scrambled and encrypted signal to its original form. Dc-emphasis - A fixed equalization which typically rolls off high frequencies in the second step of a two-step noise reduction process

Default - A value or parameter which is assumed, unless the user supplies an alternative. Many software programs supply default values and options

Default Drive - The disk drive used if no drive number is specified. For example, if drive “A” is the default, the Ms-DOS prompt will be “A>” meaning that the computer will look to drive “A” for data. The default can be changed by typing the letter of the drive and a colon, for example (B:)

Defeat - Turn off

Degausser - See HEAD DEMAGNETIZER or ERASER

Delete - To erase or remove a file. The MS-DOS command “DEL” causes files to be removed from the disk directory, opening up disk space

Delimiter - A character which is used as a boundary or separator between two data elements

Delta - The triangle-shaped grouping of S electron guns in a color CRT Cathode Ray Tube)

Demodulator - TV demodulators strip the video and audio signals from the carrier frequency. The composite video and audio can then be used as any other video or audio feed for studio use

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DES (Digital Encryption Standard) - An encryption method defined by the National Bureau of Standards.

Deserializer - A device that converts parallel digital information to serial

Desktop - PC based video teleconferencing frequently incorporates an SVGA or equivalent monitor with a video teleconferencing board set integrated into a PC.

Desktop Computer - Small microcomputer system that will fit on a standard desk

Desktop Video - A generic term used to describe the integration of video with the personal computer this may include Desktop Video Production. Interactive Video AKA Multimedia Desktop Videoconferencing, or a combination of the above.

Desktop Videoconferencing - Communication between users of desktop terminals (or PCs) that involves motion video and audio of the other party. It may also incorporate interactive computing (file or screen sharing) as well.

Detail - Resolution or definition; the clarity of a picture

Detector - The circuitry that performs demodulation.

Deviation - The maximum frequency variation of an FM signal

Device - Usually refers to a peripheral device, such as a disk drive, display screen, terminal, or printer

Diaphragm - The element in a microphone activated by sound wave vibrations. These vibrations are then converted into voltage variations which then produce an audio signal

Dichroic - A type of reflector, mirror or filter which reflects and transmits different wavelengths of light selectively, permitting a projector to provide more visible image light with loss heating of the slide or film

Diffraction - The bending or partial reflection of radio waves by metal objects

Digital - A system of recording data and images with discrete, noncontinuous codes; provides signal reproduction with little noise or distortion

Digital Optical Output - Transmits digital signals between components via a fiber optic cable which is immune to magnetic and electrical interference.

Digital Recording - Advanced, method of recording which involves a sequence of pulses or on/off signals rather than a continuously variable or analog signal: advantages are increased frequency range and lower tape noise. May be used for control, audio and video purposes

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Digital Switch - A means of supporting multiway conferencing in a fully digital network. Digital switches permit multiple users with standards-based codecs to conference, generally with voice-activated switching.

Digital Signal Processing (DSP).  Uses digital circuitry to manipulate music and soundtracks to create a sense of space.

Digital Video - This provides 500 lines of resolution for sharp picture outlines with detailed colors obtained by a wide color frequency band.

Digitize - The process of converting analog signals to numeric values (ones and zeros) that can be processed by computer

Digitizer - A device which converts analog video or sound signals into pixels that a computer can display and modify

DIN - Deutsche lndtjstrie-Norm; German standard for electronic connections which can have 3-6 pins depending on their use. All DIN plugs have the same outer dimensions and appearance

Dipole - An antenna which is made up of two active elements Direct - Not reflected

Directory - The contents or index of a disk. The DOS command “DIR’ will display the index. Other directories that contain additional indexes, known as subdirectories, may be listed using this command. Includes a file’s name, size, creation date, and creation time

Disk - Flat circular piece of magnetic storage medium used to store computer or video data, often encased in plastic, also called a floppy disk

Diskette - A small disk, usually for a personal computer, may be either BY’ or 3~’, normally encased in a plastic bolder

Disk Operating System - See DOS

Display - Output device, for presenting legible information, often a Cathode Ray Tube (CRT), a Light Emitting Diode (LED) or Liquid Crystal Display (LCD)

Dissolve - A change from one scene to another in which the outgoing and incoming visual images are superimposed or blended together for a discernible period of time as one scene fades out while the other fades in. Sometimes called cross fade or lap dissolve

Dissolve Control - A device which controls the illumination from 1,2 or more projectors in such a manner that the images fade from one into another at a fixed or variable rate

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Distance Learning - Teaching and learning situations in which the instructor and the learner(s) are geographically separated, and therefore, rely on electronic devices and print materials for instructional delivery. Teleconferencing & Distance Learning, 2nd edn, 1994)

Distortion (Audio) - A modification of the original signal appearing in the output of audio equipment that had not been present in the input. The most common way of expressing distortion is in percent of the original signal as Total Harmonic Distortion (THD)

Diversity- Receiver design which picks up a radio signal simultaneously at multiple locations and intelligently switches or combines to yield the best continuous signal

DOS - Disk Operating System; the fundamental software necessary for a computer to access disks and to load and run programs. DOS” files are commonly transferred to other program disks, eliminating the need to insert the “DOS” disk each time a program is loaded

Double Band Projector - A special purpose unit for motion picture projectors to present picture and optical/magnetic sound from two separate prints. Generally used for preliminary screenings prior to final marriage of sound track to picture. Also see INTERLOCK PROJECTOR

Downstream Keyer. A keyer that inserts the key after the effects system video output. This enables the key to remain on-air while the background and effects keys are changed behind it

Dropout - During playback, the instantaneous loss of a recorded signal due to imperfections in the tape

Drop-out Compensator - Circuit which senses drop-outs and fills in information with the preceding signal; results in no visible drop-out on the screen

Drum - Cylinder-shaped magnetic storage

DS-3 - See T3.

DSU (Data Service Unit) - A CPE component which interfaces to a digital circuit such as Ti or Switched 56. DSU performs conversion of data stream to bipolar format for transmission. Generally used (or combined) with a CSLJ.

DTS Decoding - Is a surround sound system similar to Dolby® using less compression.

Dual 56-Combination of two 56Kbps lines for a 112Kbps video transmission capacity. Dual 56 typically allows direct dialing of a videoconference call.

Dual Channel - A device with two separate paths that do not interfere unless deliberately mixed. Stereo equipment is an example

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Dual Monitor . A complete dual monitor system package contained in a cabinet for mobility.

DVD - Digital Video Disc or Digital Versatile Sisc which is a CD sized disc that can store complete video movies.

Dynamic Beam Focus - This keeps focus consistent across the entire screen.

Dynamic Mic - See MICROPHONES

Dynamic Range - The highest and lowest signal levels on a given device

E

Earth Ground - A conductor that will dissipate large electrical currents into the Earth

Echo Canceler - A device that blocks echo reflections during a conference while maintaining (apparent) full-duplex audio.

ED-Beta - Extended Definition Betamax; a video format offering 500-line horizontal resolution and Y/C connections

EDP - Electronic Data Processing

EDTV - Enhanced Definition Television also extended definition television; an advanced television system with advanced encoding and transmission methods but not as sophisticated as HDTV. Currently being transmitted in Japan, this first generation system is compatible with existing TV sets and transmission methods

Educational Television (ETV) or Instructional Television (ITV) - Generic terms applied to any television program or equipment related to some form of education or instruction

EFP (Video) - Specialized equipment for electronic field production

EGA - Enhanced Graphics Adaptor

EIA - Electronic Industries Association; the association which determines recommended audio and video standards in the US

EIAJ Standards (Video) - Videotape standards promoted by the Electronic Industry Association of Japan which allows for the compatibility of the equipment of several manufacturers

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Eight-Pin Connector - The jack often used for VCR-to­-monitor connection

EL Display. Electro luminescent display; a colored light emitting display resulting from electrical stimulation of electro luminescent semiconductors. Their slim and lightweight configuration make ELDs good for applications including multi-colored displays.

Electret - See MICROPI-IONES

Electron Beam Recording - A method for converting video images to film by applying an electronic beam directly to film emulsion

Electronic Editing (Video) - Inserting or assembling program elements on videotape without physically cutting the tape

Electronic Learning Laboratory - A system consisting of instructor control equipment and a number of student positions or stations. The control equipment is capable of producing, reproducing, monitoring and distributing programs individually or to groups of students for study and response. Distribution may be wired or wireless. Student positions usually contain headphones and possibly microphones, signaling devices, recorders and viewing facilities. May be audio or audio and visual

Electronic Viewfinder - A small picture tube ~CRT) or liquid crystal display (LCD) built into a video camera and connected to the system to enable the camera operator to see exactly what is being scanned by the camera

Electrostatic - See MICROPHONES

E-Mail - Electronic communication between computer users

Emulation - A process that allows a computer or terminal to have the characteristics of another computer or terminal Encoder (Multi-Image Devices)- A signal generator or pulses used with a tape recorder or other information storage device to produce the synchronizing signals or pulses for later decoding to operate combinations of devices often projectors) in synchronization. Compare with DECODER

Encoder (Video) - Devices that change individual component signals into composite signals. For example, an encoder combines V (luminance or light) and C (chrominance or color) signals to provide a video image. 411 video cameras contain encoders

Encryption - The scrambling of a video signal, often used in cable and pay TV systems

ENG - Specialized video equipment for Electronic News Gathering

Enter Key - Also called the RETURN KEY, this key is struck after a line of data is typed in, or after a command is typed

EPROM - Erasable Programmable Read Only Memory

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Equalizer - An electronic device which compensates for frequency inaccuracies in an audio or video system

Erase Head - A separate head on an audio or video tape recorder which erases a previous signal on the tape before it is re-recorded on. An electromagnet which disturbs the signal previously on the tape

Eraser. Tape. Bulk - A device that produces a strong alternating electromagnetic field which almost instantly erases an entire reel, cassette or cartridge of tape. Also called bulk demagnetizer or degasser

ERP - Effective radiated power, the actual power radiated by a transmitter antenna

Error - Any operation or interaction with a computer that does not follow the predetermined syntax

European Television - The standard television system in second as opposed to the NTSC system used in the US, which is 525/60)

Exciter Lamp- The small lamp which projects its single-coil illumination through the optical sound track on 16mm film; the varying light intensity is read by the projector photoelectric cell which converts the light impulses into electronic signals which are amplified and made audible by a loudspeaker or earphones

Execute- To run a program, or to carry out an operation

Expander - A circuit which expands the dynamic range of a signal by a finite ratio, typically 1:2 in a compander system

Expansion Slots -  Open connectors for the attachment of various computer peripheral devices, such as modems or monitors. EXPANSION SLOTS provide a common connection (I/O channel) for optional equipment

Extension - A 3-character suffix to a filename. Extensions are normally used to identify what type of data is in the file -whether the data is text, an application, a resource, and so on

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