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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 and 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.
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
Definition - The sharpness/resolution of a picture
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 3 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
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 micro-computer 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
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 soundwave 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 less heating of the slide or film
Digital - A system of recording data and images with discrete, noncontinuous codes; provides signal reproduction with little noise or distortion
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
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.
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 Industrie-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
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 51/4" or 31/2", normally encased in a plastic holder
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
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)
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 T1 or Switched 56. DSU performs conversion of data stream to bipolar format for transmission. Generally used (or combined) with a
CSU.
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
Dual Monitor - A complete dual monitor system package contained in a cabinet for mobility.
Dynamic Mic - See MICROPHONES
Dynamic Range - The highest and lowest signal levels on a given device.
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