D

DAC (A/V, communications, computer)
Digital-to-Analog Converter. DAC is the electronic device used to convert digital audio and video signals stored on CD-ROMs, DAT, or in computer files - to analog signals that can be reproduced by conventional stereo and television components (see Digital-Analog).

Daisy Chain (communications, computer)
Devices connected in series (screens, printers, video tape recorders, etc.), from one to the other through cabling. Communications to these devices start at the first device and are then looped to the second, third, fourth, to as many on the "chain". In an integrated circuit (IC), an interrupt priority arrangement where the interrupt bus is searched serially.

Daisy Wheel (computer, printer)
Older style printers (1970's/80's) that use plastic, fibreglass, metal hubs with spokes. At the end of each spoke is a character (alphanumeric and special characters). The daisy wheel spins to the correct character position that is to be printed and a print hammer drives the spoke with the character on the tip of the spoke impressing the image of the character, onto an ink ribbon, which then imprints the image onto the paper. These have been replaced by dot matrix, laser printers, and ink-jet printers.

Damping (computer, electronics)
Technique that is used to stabilize an electronic circuit by preventing excessive or undesirable oscillations from occurring.

Dark Current (A/V, computer/photonics)
In Audio/Visual terminology, the current flowing from a pickup tube even when the lens is capped and there is no exposure to an image at all. Dark current is roughly the equivalent of base fog level on a film negative. Similarly, in optical computing terminology, the current output of a detector even when no light is incident upon it.

Dark True Logic: DTL (A/V, computer/photonics)
Term used in optical computing to define an optical logic system where "TRUE" may be represented by a low intensity of light, and "FALSE" by a high intensity of light.

DASD (computer)
Direct Access Storage Device - pronounced "dazdee" - any peripheral device that is directly addressable by the computer, such as a disk or diskette drive.

DAT (A/V, computer)
Digital Audio Tape - a CD-quality digital recording technology for magnetic tape. The 4mm DAT drive can hold over one gigabyte (1,000 Megabytes) of data and is used as a high-capacity backup medium for computers. Also, a process of recording sound in helical bands on a tape cartridge. This process is similar to recording video signals.

Data (communications, computer)
Any type of information to be acted upon by some process. It can be in hard copy or electronic format. In computers, data indicates digitised information that is to be acted upon by computer instructions (software). Generically the term is used to denote facts, numbers, letters, symbols, binary bits presented as voltage levels in a computer. In a binary system data is represented by "0s" or "1s".



Data Acquisition (communications, computer)
Collection of data from electronic devices within an environment (aircraft, factory, weather station, satellite, etc.) This type of collection of information, through communications, can also be called "telemetry". Data Acquisition can also be used as a term for collecting information, in general, that is to be processed by a computer.

Data Administration (computer)
Term used originally, in centralised computing environments, for a department or division within the Management Information Systems that administrates all forms of data.

Database (computer)
Program used to manage data with powerful software routines that allow for the manipulation of data into many different uses (sorting, extracting, reporting etc.).

Database Administrator (computer)
Person assigned to a database that may be responsible for the management and administration of the database within an organisation.

Database Management System (computer)
Software that controls the organisation, storage, retrieval, security and integrity of data in a database. When a database management system (DBMS) is used, information systems can be changed more easily as the organisation's requirements change. New categories of data can be added to the database without disruption to the existing system.

Database Manager (computer)
Software that provides the management tools for all database files.

Database Server (communications, computer)
Computer that may be dedicated to database management functions, within a Local Area Network, as opposed to a File Server, which can manage any or all types of files.

Data Bits (communications, computer)
Term sometimes used to describe the number of bits, in serial communications mode, that comprise each character transmitted or received.

Data Buffer (communications, computer)
Temporary storage register in a CPU (central processing unit) or peripheral devices capable of receiving or transmitting data at different Input/Output (I/O) rates.

Data Bus (computer)
Within a computer, the electronic channel or path that data is sent to the central processor on. In many computers the data bus is separate from the instruction bus or the utility bus where instructions and utilities are used to act upon the data coming through the data bus.

Data Carrier (communications, computer)
Any device or medium used to store machine readable information (disks, tape, chips). It can also refer to a communications channel or frequency onto which information is modulated for transmission through a network.


Data Cartridge (computer)
Any device that is removable from the computer such as a removable hard drive or removable streaming tape cartridge that can be stored away from the computer.

Data Centre (computer)
In mainframe and minicomputer environments, a center that supports all of the computing systems (centralised computing).

Data Circuit-Terminating Equipment (communications, computer)
Equipment that provides the signal conversion and coding between the data terminal equipment (DTE) and the line. The Data Circuit Equipment (DCE) may be separate or an integral part of the DTE. The DCE may perform other functions that are normally performed at the network end of the line or connection.

Data Collection Device (computer)
Term used to describe a device that allows direct data entry in such places as factories and warehouses. Digital sensors for monitoring heat, light, air are collection devices (telemetry).

Data Communications (communications, computer)
This term had been used to differentiate between voice communications, however, in recent usage the term "communications" now represents voice, data, graphics, image, real motion communications. In summary, communications means the electronic transfer of information between computers or between any point and any other point. Data communications used to refer to digital information, but recently, and in the near future almost all communications, no matter what form, over short or long distances, will be digitised.

Data Compression (communications, computer)
Method of condensing data (information) into its smallest possible form, through the use of algorithms, in order to reduce both the storage size and transmission size of the information. Recent developments in compression techniques have realised a compression ratio of 100 to 1 or better. In the near future, compression ratios will reach 1,000 to 1. This is especially important for real time, full motion, high definition, colour video information.

Data Definition (computer)
Defining and disciplining data into fields, formats, files, records through high level programming. In database management systems, the data definition program manages data by structuring and coding information so as to provide many different ways of sorting, extracting, reporting, and presenting it, from the database to end-users.

Data Definition Language: DDL (computer)
Term used to specify the way in which data is to be stored and managed in a database by a database management system (DBMS). The defined data is referenced by data manipulation language (DML) commands as part of the programming language.

Data Element (computer)
In a database program, any element, segment, or unit of information that has been defined as a significant part of a file or record that can be acted upon (for example, name, address, street, city, state, country, postal code, etc.).



Data Encryption (communications, computer)
Term used to refer to the use of cryptographic methods in computer communications for transforming information for the purpose of making the message unintelligible to all but the intended receiver of the information. It also implies the additional goals of providing assurance to the receiver that the information is not a forgery; allowing the receiver to prove to a third party that the information is not a forgery. The transformation used to encipher information typically involves both a general method, or algorithm, and a key. While the general method used by a pair of correspondents may be public knowledge, some or all of the key information must be kept secret. The process of transforming (enciphering) information is to apply the enciphering algorithm to the information, where the key is used as an auxiliary input to control the enciphering. The reverse operation (deciphering) is performed in a similar manner. The most widely used cipher in the U.S.A., for encryption of stored or transmitted computer data is the Data Encryption Standard (DES) approved by the National Bureau of Standards, in 1976.

Data Encryption Standard: DES (computer, communications)
Standard that can now be used with personal computers, for encrypting information that encodes information, at random, but that uses a key at each end of the communications to decipher (decode) the same information. The DES enciphers a 64-bit message block under control of a 56-bit key to produce a 64-bit ciphertext.

Data Entry (computer)
Traditional term used to describe the actual input of data into a database or information processing system. This can include many different ways of entering information, utilising a keyboard, a modem, a scanner, an optical character recognition device, a mouse, a graphics tablet, and, of course, through keystrokes from the keyboard.

Data File (computer)
Term used to describe any file created within an application such as a word processing document, a spreadsheet, a database file, a chart or graph; it is also known as a document.

Data Flow (computer, communications)
Channel or path of information from its source to processing, to final presentation. In communications, the channels or routes that information travels from its origination to its final destination, including all subroutes, re-routes, through all network nodes.

Data Flow Systems (computer)
Alternative to conventional programming languages and architectures, in which values rather than value containers are dealt with, and all processing is achieved by applying functions to values to produce new values. These systems can realise large amounts of parallelism (present in many applications), and effectively utilise very large scale integration (VLSI) technology. Much progress has been made in their development, and several prototypes are operational.

Data General Corporation (computer)
Computer company founded by Edson de Castro, in 1968.

Datagram (communications)
In Packet Switching, a self-contained packet, independent of other packets, that does not require acknowledgement, and that carries information sufficient for routing from the originating data terminal equipment (DTE), without relying on previous exchanges.
Data Independence (computer)
Database management fundamental whereby a database structure can be changed without corrupting or changing the existing database management system.

Data Integrity (computer)
Methods that are used to prevent loss or alteration or corruption of a database.

Data Line (computer, communications)
Traditional term used to describe a circuit or a communications link that carries data (as opposed to a voice or a video communications circuit).

Data Line Monitor (communications)
Testing device used by technicians to analyse the signalling and timing characteristics of a communications circuit by visually displaying a series of reference patterns.

Data Link Layer (communications)
Layer 2 of the OSI (Open System Interconnection) Model; it assists in converting an unreliable transmission channel into a reliable one.

Data Link Protocol (communications)
In communications, the transmission of a unit of data from one node to another (Layer 2 in the OSI model). It is responsible for ensuring that the bits received are the same as the bits sent. The following are the major categories of data link protocols: Asynchronous, Synchronous, Isochronous Transmission, and Local Area Network protocols.

Data Management (computer)
Part of an operating system or software routine that enables the management of information by the personal computer such as physical storage locations of information (disks, tapes, optical drives, etc.) as well as the retrieval of the information.

Data Model (computer)
Organisation description of a database or database management system (DBMS).

Data Network (communications)
Traditional name for a network that communicates "data" as opposed to voice or video (TV) information. This differentiation is becoming blurred with the arrival of all digital networks (voice, data, video, real-time, full motion colour, over the same network).

Data Point (computer)
Term sometimes used to describe a value represented by a bar or symbol in a graph.

Data Pointer (computer)
Register holding memory address of the data (operand) to used by an instruction.

Data Processing (computer)
Traditional name for processing data, as opposed to word processing, voice processing, video processing. Recently, the term is giving way to a new term called information processing which integrates voice, data, full-motion, real-time, high definition color.


Data Processing Management Association: DPMA (computer)
DPMA is one of the largest worldwide organizations serving the information processing and computer management community. It was founded in Chicago as the National Machine Accountants Association and charted in Illinois on 26 December, 1951. DPMA comprises all levels of management personnel and, through its educational and publication activities, seeks to encourage high standards of performance in data processing.

Data Processing Systems (computer)
Traditional name for electronic, electromechanical, or mechanical machines for transforming information into suitable forms in accordance with procedures planned in advance. The term data processing system is also applied to the scheme, or procedure, that prescribes the sequence of operations to be performed in processing the information.

Data Projector (A/V, computer)
Video projector that accepts output from a computer and projects it onto a large screen or wall for audience viewing.

Data Rate (computer, communications)
Speed of data transfer within a computer or between a peripheral device and a computer; or, the speed of data transmission within a communications network.

Data Reduction (computer)
Transformation of information, usually empirically, or experimentally derived, into corrected, ordered, and simplified form. The term generally refers to operations on either numerical or alphabetical information digitally represented.

Data Set (computer)
In software terminology, a data set may be described as a compilation of information containing the name of the data set, its boundaries in physical storage and certain characteristics of the data items within the set. In hardware terminology, a data set generally defines a device used to connect a computer data bank to a telephone line.

Data Structure (computer)
Physical layout of data. Data fields, memo fields, fixed length fields, variable length fields, records, word processing documents, spreadsheets, data files, database files and indexes are all examples of data structures.

Data Switch (computer, communications)
Device that changes the direction of data. It can be as simple as a black box that switches data from one terminal to another, from one printer to another, or as complex as a digital system that automatically routes data to a large number of terminals.

Data Tablet (computer)
Traditional term used to describe a manual input device for graphics display consoles. It consists of a flat writing surface (the tablet itself) and a stylus, typically the size of a ballpoint pen, which the user moves over the tablet as if writing on a normal note pad.

Data Terminal Equipment: DTE (communications, computer)
Equipment consisting of digital devices that convert the user information into data signals for transmission, or reconvert the received data signals into user information.

Data Transfer (computer)
Traditional term used for the movement of data within a circuit, or computer, or network.

Data Transfer Rate (computer)
Speed with which data can be transferred to or from a disk and a computer.

Data Transmission (communications)
Traditional term used to describe moving data over a network. It is being supplanted by newer terms that include voice, data, real-time full motion, high definition, colour video.

Data Type (computer)
Types of data being computed. Some of the types are numeric, alphanumeric, dates, and logical (true/false) data. Each programming language allows for the creation of different data types. When a data type is created, it cannot be treated like another data type. For example, alphanumeric data cannot be calculated, and the digits within numeric data cannot be separated. Data types for calendar dates can only contain valid dates and date formats (i.e. yyyy/mm.dd).

Date (computer/DOS)
DATE in DOS sets the current date in the computer. The displayed date can be accepted by pressing ENTER, after DATE, or a new date can be typed in to change the date on the computer. DOS will maintain this new setting during the current session.

Date Field (computer)
Term describing a field in a database program used for dates and that may automatically be limited to eight characters, including slashes used to separate the month, day, and year.

Daughterboard (computer/microelectronics)
Small, printed wiring board plugged into a multi-pin connector (header) on an adapter card or the computer's motherboard. A daughterboard performs a function that is not a standard feature of the adapter card or the computer.

dB - Decibel (A/V, communications)
Measurement of the loudness or strength of a signal. It is a measure of the relative strength of two signals. The number of decibels is 10 times the log of the ratio of the power of two signals, or 20 times the log of the ratio of the voltage of two signals. The term dB is the abbreviation for decibel. The decibel, one tenth of a Bel, is the fundamental unit of audio-sound intensity. It is a logarithmic unit corresponding numerically to perceptions of sound intensity by the human ear. Sound at 40 dB is perceived to be twice as loud as sound at 20 dB. The form db is also used in some definitions.

DBMS (computer)
Database Management System (abbreviation).

DBS - Direct Broadcast Satellite (communications)
One-way (for now but two-way is coming, soon) broadcast (narrow-cast) service direct from a satellite to a user's dish (antenna). DBS providers are preparing to deliver individual information services as well as public and commercial Television services.



DBX (A/V)
Noise reduction used by BTSC (MTS/SAP) stereo TV decoders. It takes the compressed audio signal that is transmitted and then expands the signal to its original dynamic range.

DB# (computer, communications)
Series of jacks, plugs, connectors with differing numbers of sockets or pins (DB-9, 15, 25, 37, 50, etc.) that connect a wide variety of computers and communications devices. The letters DB determine the physical size and structure of the socket or pins:

a) DB-9, DB-25: RS-232 interfaces, DB-25 also for parallel printer pins);
b) DB-15: Used in the IBM PS/2 Series (15 pins rather than 9 pins).

DC: Direct Current (computer, electronics)
Electrical current that flows continuously, as opposed to Alternating Current (ac).

DCTL: Direct Coupled Transistor Logic (computer, microelectronics)
Logic employing only transistors as active circuit elements.

D-CART (A/V, communications, computer, M/M)
Digital Cartridge Editing System - recording audio information as digital data on magnetic or optical disks so that a computer system can search, scan, edit, and re-broadcast the information immediately. With D-Cart no magnetic tape is required other than the original source material. Audio material such as interviews, ambient sounds, background sound, is gathered by radio reporters with tape recorders and sent back to the studio, where it is transferred to computer hard disk. On screen, the sound appears as a text document, with a listing of its file, reporter's name and duration. To edit, the item is called up and manipulated as sound-on-screen, using a pad that guides the cursor across a thin band, representing an imaginary tape. Audio segments can be turned on/off by clicking the pad along the "on-screen tape", where the desired sound bite exists (it can also be "cut", merging sound bites into a story, with voice-over narration).

DCE (computer, communications)
Data Communications Equipment or Data Circuit terminated Equipment - devices used to originate, maintain, and terminate a communications session on a network.

D-DAT (computer)
Digital audio tape format for data. The tape can be divided up into 254 partitions and provides for updating in place. D-DAT tape serves as both backup and standby storage.

DDE: Dynamic Data Exchange (computer, Windows)
Message protocol in Microsoft Windows that allows application programs to request and exchange data automatically. A program in one window can query a program in another window using the DDE protocol. DDE is an Interprocess Communications (IPC) method used by Windows and OS/2 to transfer data between two different applications.

DDS: Dataphone Digital Service (communications)
Private line digital service from AT&T that provided data rates from 2,400 bps up to 56Kbps. Private analog lines can also be connected to DDS lines.

DDS: Digital Data Service (communications)
Private line digital services from non-AT&T common carriers (MCI, Sprint, etc.).

Deadlock (computer)
Term sometimes used to describe the condition whereby each of two programs needs resources that are held captive by the other and neither is willing to release the resource it has until it can access the resource that the other program is holding captive. A task (process) in a multiprogramming system is deadlocked if it cannot proceed because it is waiting for an event that will never occur. A system deadlock or a deadlock situation exists if one or more tasks in a system are deadlocked.

Debeaming (A/V)
Gradual reduction of scanning beam intensity. The picture on a picture tube becomes a high-contrast picture, with detail in the white and black areas no longer visible, gradually deteriorating into a non-distinct, light-grey screen.

Debug (computer/DOS)
To remove errors in the source code for an application. To identify, investigate and eliminate faults in program routines.

In DOS the DEBUG command starts the DEBUG program, which lets the user test and monitor executable files. This program is designed to help the user to find errors in other programs. Since the DEBUG program works in assembler code, the user should only use this program if they are familiar with assembler code.

Debugger (computer)
Programmer or a specialised "expert system" program that assists a programmer in removing errors in source code for an application.

DEC (computer)
Anagram and trade name for Digital Equipment Corporation (bought out by COMPAQ).

Decay (A/V, computer, M/M)
Rate that a sound reduces in amplitude from its initial maximum volume. Decay follows Attack and precedes Sustain.

Decentralized Computer System (computer)
Term used to describe a system in which the computer and some storage devices are in one location, but the devices that access the computer are elsewhere.

Decentralized Processing (communications, computer)
Method of computing developed in the 1980's allowing communications between a mainframe or minicomputer in a central or corporate office to communicate selectively with regional or district computers (not to be confused with distributing computing).

Decibel (communications)
Reference measurement for the loudness of a voice over telephone, it can also be used for measuring the signal strength of a particular connection. It is a measure of the relative strength of two signals. The number of decibels is 10 times the log of the ratio of the power of two signals, or 20 times the log of the ratio of the voltage of two signals.



Decimal (computer, mathematics)
System of numerical representation which uses ten numerals (0,1,2,3,4,5,6,7,8,9), each numeral being called a digit. A numbering system to the radix of 10.

Decision Instruction (computer)
Special instructions in a computer program that compare sets of data with other sets of data that will then branch (go to) another part of the program.

Decision Logic Table (computer)
Standard table of the logical decision that must be made regarding potential conditions in a given system; also called a decision table.

Decision Support System (computer)
Computer system that support managers in nonroutine decision-making tasks.

Decision Symbol (computer)
Standardised symbol (diamond) to indicate a decision in a computer programming flowchart where it is identified within the symbol and the path or route of the decision branches off from the symbol.

Decision Table (computer)
Standard table of the logical decisions that must be made regarding potential conditions in a given system; also called a Decision Logic Table. Decision tables are a tabular method of describing or specifying the various actions associated with a combination of conditions. The method is tabular: it uses a special form to present the associations.

Decision Theory (computer, mathematics)
Concepts and techniques which have been developed to both describe and rationalise the process of decision making; making a choice among several possible alternatives.

Declaration (computer)
Statement creating a user-defined data type, naming a variable, or creating a constant.

Declare (computer)
In text and not as a keyword in programming, to create a user-defined data type, data holder for a variable or constant. As a keyword in BASIC language for writing Windows applications, to register a function contained in a dynamic link library in a code module.

Decoder (computer, communications)
Device and/or program that decodes information received in a coded format.

Decollating (computer)
Process of removing carbon paper from layered copies of multiple-copy computer paper.

Decompress (computer)
Specialised software program that restores compressed information to its original state.

Decremental (computer)
In computers a binary method used to subtract one number (or series) from another. In the CPU, a decrement is a value that is subtracted from the contents of a register.

Dedicated (computer)
Refers to computers programmed only for a single, specialized application.

Dedicated File Server (communications, computer)
In Local Area Networking, a file server that performs only that function and no other computing or other application functions.

Dedicated Circuit/Channel (communications)
Term used to describe a communications circuit or channel that is dedicated to the purpose it is intended (as opposed to a switchable or virtual circuit/channel).

De Facto Standard (computer, communications)
Format, or language, or technique, or product, or service that is widely used and copied, but has not been officially sanctioned by a standards organisation.

Default (computer)
Value assigned to a variable, argument of a function, or parameter of a keyword if not explicitly declared in the statement containing it. A drive or device setting that is automatically assumed by a computer system (default drive is drive "C", etc.).

Default Button (computer/Windows)
Command button in some dialog boxes selected as the most logical choice. This button has a bold border when the dialog box appears, and pressing ENTER chooses the button.

Default Condition (computer)
Value set by software when a user elects not to make a choice available in a particular situation.

Default Drive (computer)
Drive to which commands refer in the absence of any specified drive. An application program stores files on the memory device in the default drive (also, current drive).

Default Filename Extension (computer/DOS)
Extension an application will use automatically unless a different extension is specified.

Default Printer (computer/Windows)
Printer that Windows applications automatically use when choosing the Print command, without first specifying which printer is required for a particular application.

Default Settings (computer)
Settings automatically used by a program unless the user specifies otherwise.

Default Shell (computer/Windows)
Shell program that runs automatically starting Windows; also the program used to end a Windows session. Initially, the default shell for Windows is Program Manager.

Defragmentation (computer)
Process of moving hard-disk data clusters. Defragmentation physically locates the content of files on the drive in the sequence of the data it contains. Defragmentation applications, such as Symantec's Norton SpeedDisk are also disk data, or disk information organizers.

Defect (computer)
Any deviation from the normally accepted characteristics of a product or component.

Definition (A/V)
In Audio/Visual terminology, the clarity of the detail of a television picture.

Deformable Mirror Device: DMD (computer/photonics)
Term used in optical computing to define a spatial light modulator consisting of a deformable reflecting membrane suspended above an array of small wells.

Degausser (A/V, computer)
Circular magnetic instrument used to de-magnetize a TV or monitor (cathode ray tube surface). It can also be a hand-held or flat-bed scanner-type device used to de-magnetize a computer storage disk or computer storage tape. The degausser for picture tubes demagnetizes the screen for colour purity.

Degenerate Four Wave Mixing (computer/photonics)
Four-wave mixing whereby the frequencies of light for all four waves are the same.

DEL or ERASE (computer/DOS)
DEL removes one or more files from a disk. DOS deletes files by changing the file entry on the file allocation table so that the disk space file used is marked as available. DOS will then use that disk area to store other files.

Delay (communications, computer/microelectronics)
Slowing up of the propagation of a pulse either intentionally, such as to prevent inputs from changing while clock pulses are present, or unintentionally that can be caused by transistor rise and fall time pulse response effects.

Delay Distortion (communications)
Distortion of a signal occurring when the propagation delay for the transmission medium is not constant over the frequency range of the signal.

Delay Line (communications)
Transmission line or an electrical network approximation of it which, if terminated in its characteristic impedance, will reproduce at its output a waveform applied to its input terminals with little distortion but at a time delayed by an amount dependent upon the electrical length of the line. Delay lines are used for establishing a time sequence for the occurrence of events. A delay line with a total length equal to the greatest time delay required in a system may be used as a basic, testing, reference point.

Delegation Control (A/V)
Buttons on a video switcher device that determine the function of the switch buses.

Delete (computer)
Remove information from a screen, file, computer program, memory.

Delete Key (computer)
Key (DEL) on a keyboard used to delete information on the screen or in the computer.



Delimiter (computer)
Code or special character generated from the keyboard that distinguishes one type of information from another, typically used in databases but also for word processing and spread-sheet type applications.

Delta Gun (A/V)
TV tube in which the electron guns are arranged in a triangular configuration or delta configuration.

Delta Modulation (communications)
Technique to sample voice waves and convertto digital code. Delta modulation typically samples the wave 32,000/second, but generates only one bit per sample (see PCM - Pulse Code Modulation).

Delta-Sigma Modulation (communications)
Also called Sigma-delta modulation, it is a type of differential pulse code modulation (DPCM). With delta-sigma modulation, the difference (delta) used to convert to and from digital and analog signals is based on the sum (sigma) of a number of preceding samples rather than the preceding sample itself. Delta-sigma modulation is used with 1-bit converters and requires high values of oversampling: 64x is common in consumer, audio CD drives (Sigma-delta Modulation has the same definition).

Demand-Assignment Multiple Access (communications)
Allocating satellite communications and transceiver capacity, based on either FDM (frequency division multiplexing) or TDM (time division multiplexing), in which capacity is granted on demand.

Demodulator (communications, A/V)
Stage in a receiver device at which demodulation of the received signal takes place. In a tuned radio frequency (rf) receiver, the demodulator separates the audio frequency (af) signal from the amplified incoming rf carrier signal. A demodulator is often call a detector. In a superheterodyne receiver, the rf signal is separated from the carrier signal at the second detector, because the converter or first detector merely serves to change the modulated rf carrier signal to a modulated intermediate frequency carrier signal. In a frequency modulated receiver the demodulator converts carrier frequency changes into corresponding audio signals. In a colour television receiver, the demodulator extracts the colour difference signals from the incoming modulated carrier signal (see Detector).

Demultiplex (communications)
Method, or device used to differentiate and determine a specific signal or set of information from a multiplexed signal of many different signals and sets of information.

Dense Wave Division Multiplexing: DWDM (computer, communications)
The capability of introducing different wave-lengths of light onto a single fibre optic carrier (or fibre strand) thereby enabling the transmission of multiple carriers, or channels, or frequencies of light waves over the same optical fibre element (typically, to the human eye, this can be perceived as "shades of pink" light, emitting from the end of the fibre optic element). Basically this provides much greater communications capacity over existing fibre optic cable. For example, if a single fibre can communicate digital information at 2 Gigabits per Second, with a DWDM device that creates four frequencies of light on the same fibre element, the effective communications increase would represent 4 x 2 Gbit/sec, or 8 Gigabits per Second.

Density (A/V, computer, M/M)
In computer terms, the amount of data stored on magnetic tapes, expressed in numbers of characters per inch (cpi) for magnetic tape, or bytes per inch (bpi). In Audio/Visual terms, the number of events within a certain time unit. Visual density can be expressed as a multiple superimposition or key, or successively as a series of quick, montage-like cuts. Audio density may be a chord consisting of many notes or a rapid series of many notes, or simultaneous playing of several audio tracks.

Dependent Service (computer/Windows)

Service that requires the support of another service. For example, the Alerter Service is dependent on the Messenger Service, in the Windows networking operating system.

Depth of Field (A/V)
Distance between closest and furthest points in focus as seen by a video camera. The higher the F-stop number, the greater the depth of field. Depth of field is dependent upon: focal length of the lens, f-stop, and distance between object and camera.

Depth Staging (A/V)
Arrangement of objects, when presented on a television screen, so that foreground, middle-ground, and background objects are clearly defined.

DES (Data Encryption Standard) (communications, computer)
Standardized technique that scrambles data into an unbreakable code for transmission over public networks. It uses a binary number as the key for encryption that offers more than 72 quadrillion combinations. The number, which can be randomly chosen for each transmission, is used as a pattern to convert bits at both ends of the transmission.

Descenders (computer)
Elements or portions of typed or printed characters that are printed or displayed below the reference line for all other characters (examples are g,j,p,q,y).

Descending (computer)
Ability to sort files or records in descending order rather than ascending order; from Z to A rather than from A to Z - or from 999 to 0 rather than from 0 to 999.

Design Mode (computer)
One of two modes of operation of Visual Basic, also called design time. The design mode enables the creation and modification of forms and control objects, entering code, and execution of the application. The other mode is "run", the executing of the operation.

Desktop (computer/Windows)
Screen background for Windows on which windows, icons, and dialog boxes appear.

Desktop Pattern (computer/Windows)
Geometric pattern that appears across the desktop. The Control Panel can be used to design personal preferences for patterns or for one of the numerous available Windows patterns.

Desktop Publishing (computer)
Term used to describe the creation of publishing material using a personal computer, and peripheral devices such as scanners, optical character recognition, and laser printers. Software package for designing and producing professional-looking documents.



Destination Directory (computer/Windows)
Directory to which a copy of one or more files is intended to be sent to.

Destination Document (computer/Windows)
Document into which a package or a linked or embedded object is being inserted. For an embedded object, this is sometimes also called the container document.

Detailed Logic Diagram (computer/microelectronics)
Diagram depicting all logic functions and also showing non-logic functions, socket locations, pin numbers, test points, and other physical elements necessary to describe the physical and electrical aspects of the logic. The detailed logic diagram is used primarily to facilitate the rapid diagnosis and localisation of equipment malfunctions. It is also used to verify the physical consistency of the logic and to prepare fabrication instruction. The symbols are connected by lines that represent signal paths.

Detector (communications)
Device used to remove the original modulating signal from a modulated wave. In communications systems, and in some data storage systems, the information to be transmitted is impressed upon a periodic wave called the carrier; the carrier is then said to be modulated. After reception, the original modulating signal is recovered by demodulation or detection (see Demodulator).

Detritus (computer/microelectronics)
Fragments of material produced during resistor trimming that remain in trimmed areas.

Development Tool (computer)
Hardware devices, software program or combination of each, which assists designers and programmers to design and develop a computer system.

Device (computer/DOS)
Unit of processing equipment in a computer system external to the CPU (central processing unit); synonymous with "peripheral".

DEVICE command in DOS loads a device driver into memory when DOS reads the CONFIG.SYS file. Device drivers offer additional features, including on-screen graphics, changing code pages, creating virtual drives, disk caching, using additional hardware.

Device Contention (computer/Windows)

Method used by Windows network software to allocate access to peripheral devices, such as a modem or a printer, when more than one application is trying to use the same device.

Device Context (computer/Windows)
Windows term for a record or structure containing a complete definition of all variables required to fully describe a window with a graphic object. Variables include dimensions of the graphic area (viewport), drawing tools (pen, brush) in use, fonts, colours, drawing mode, and so on. Windows provides a handle (HDC) for each device context in use.

Device Driver (computer/DOS/Windows)
Program enabling Windows or DOS to use a device (such as an external disk drive) or adds some capability to DOS or Windows. Drivers are installed by means of commands in the CONFIG.SYS file (i.e. SMARTDRV.EXE, RAMDRIVE.SYS, EMM386.EXE).

Device High (computer/DOS)
DEVICEHIGH command in DOS loads a device driver into reserved memory when DOS reads the CONFIG.SYS file. Device drivers offer additional features including on-screen graphics, changing code pages, creating virtual drives, disk caching, and using additional hardware such as a mouse. Not all device drivers can be loaded into reserved memory.

Device Independent Colour (A/V, computer, printing)
Standard designed to allow consistent results when an image is transferred from the computer screen to paper or film and vice versa (example "Pantone" Color Coding).

Dew Indicator (A/V)
Indicator that will automatically operate if there is excess moisture in a camera or video recorder and will shut the unit down for a period of time (usually 30-60 minutes).

Diagnostic Message (computer)
Message that informs the user of programming language syntax errors.

Diagnostic Program (computer)
Program designed to check for proper operation of the various hardware parts of a microcomputer (CPU, memory, keyboard, display, etc.).

Dialog Box (computer)
Pop-up window requesting information from users. Dialog boxes include message boxes, input boxes, and user-defined dialog boxes for applications such as choosing files to open. In Windows, dialog boxes offer warnings or explain why a command can't be completed.

Dial-Up Network (communications)
Switched telephone network regulated by the FCC, administered in the U.S.A. by common carriers, such as AT&T, MCI, Sprint, the Bell operating companies and others.

Diamond Powder (computer/microelectronics)
Powder or grit used mainly as abrasives for processes such as lapping and polishing, abrasions and abrasive trimming, or to create the cutting surface of slicing equipment.

Diaphragm (A/V)
In Audio terminology, the vibrating element inside a microphone that moves with the air pressure from the sound. In Video terminology, adjustable lens-opening mechanism that controls the amount of light passing through a lens.

Diazo Film (A/V)
Film used to create copies of microfilm or microfiche. Diazo film is exposed to the original film under ultraviolet light creating a copy with the same polarity as the original film. Negative originals create negative copies and positive originals create positive copies. Diazo copies can be created in different colours (blue, blue-black, purple).

DIB (computer/Windows)
Device-Independent Bit map - a Windows-specific bit map format designed to display graphic information. DIB files take the extension DIB and are similar to BMP format.

Dichroic Filter/Mirror (A/V)
Mirrorlike colour filter that singles out, from the white light, the red light (red dichroic filter) and the blue light (blue dichroic filter), with the green light left over.

Die (computer/microelectronics)
Tiny piece of semiconductor material, broken from a semiconductor slice, on which one or more active electronic components are formed (also called a "chip").

Die Bonding (computer/microelectronics)
Attaching a semiconductor chip to a substrate, with an epoxy, or solder alloy.

Dielectric Isolation (computer/microelectronics)
Use of silicon dioxide barriers created during silicon IC (integrated circuit) processing to provide isolation between components on a chip.

Difference Engine (computer)
Machine designed by Charles Babbage to solve polynomial equations by calculating the successive differences between them.

Differential Encoding (communications, computer)
Method of encoding digital data on a digital signal such that the binary value is determined by signal change rather than signal level.

Differential Gain (A/V, communications)
Difference in output amplitude (percentages or decibels) of a small, high frequency sine wave signal at two stated levels of a low frequency signal upon which it is superimposed.

Differential Phase (A/V, communications)
Difference in output phase of a small high frequency sine wave signal at two stated levels of a low frequency signal on which it is superimposed.

Differential Pulse Code Modulation (communications)
Process used by 1-bit converters to encode and decode digital sound or video data based on the difference between successive samples rather than the actual value of the sample. DPCM provides better sound quality for the same number of bits per sample or enables digitised sound or video data to be stored in smaller files by compression.

Diffused Light (A/V)
Light that illuminates a relatively large area with an indistinct light beam. Diffused light, created by floodlights, produces soft shadows.

Diffusion (A/V, communications, computer/microelectronics)
In Audio/Visual Production, the displacement of light, through a filter or gauze so as to reduce or eliminate glare. In microelectronics, a process used in the production of semiconductors, which introduces minute amounts of impurities into a substrate material such as silicon or germanium thus permitting the impurity to spread into the substrate. The process is very dependent on temperature and the length of time of diffusion.



Diffusion and Oxidation System (computer/microelectronics)
Process whereby non-conductive materials are made semiconductive by diffusing controlled amounts of selected impurities into the surface: the surface of the silicon is then oxidised selectively to provide a protective or insulative layer. Diffusion and Oxidation are accomplished by exposing the silicon wafer to specific atmospheres in a high temperature, electronic oven or furnace.

Diffusion Depth Testing (computer/microelectronics)
Device and method for determining what depth diffused impurities have been implanted into a silicon wafer under hot ion implantation.

Diffusing Filter (A/V)
Lens attachment that gives the scene a soft, slightly out-of-focus look. This is sometimes special-effected by shooting through an acrylic gauze in front of the camera lens.

Digital-Analog Conversion (communications, computer)
Electronic devices used to convert digital audio and video signals, stored on magnetic media or on CD-ROMs, DATs, to analog signals that can be reproduced by conventional stereo and television components. DACs (abbreviation) present the results of digital computation, storage, or transmission, typically for graphical display or control of devices that operate with continuously varying quantities.

Digital Audio Tape: DAT (A/V, computer)
Type of tape or a recording format that requires the digitisation of analog data (sound and/or music, in this case) and provides near-perfect reproduction of masters and copies.

Digital Camera (A/V, computer)
Video camera that records information in digital form. Unlike traditional analog cameras that convert light intensities into infinitely variable signals, digital cameras convert light intensities into discrete numbers. The camera microelectronics code the information into pixels (dots), test each pixel for light intensity, and convert the intensity into a binary number. In a colour digital camera, 3 numbers are created; the amount of red, green and blue in each pixel.

Digital Computer (computer)
Any device for performing mathematical calculations on numbers represented digitally; by extension, any device for manipulating symbols according to a detailed procedure or recipe. The class of digital computers includes microcomputers, conventional adding machines and calculators, digital controllers used for industrial processing and manufacturing operations, store-and-forward communication equipment, and electronic information processing systems.

Digital Computer Programming (computer)
The art of writing instructions to control the operation of a stored-program digital computer. More generally, programming refers to the analysis and planning of a solution to a problem, in which the phase of instruction writing is referred to as coding.

Digital Control (computer)
Using digital or discrete technology to maintain conditions in an environment as close as possible to desired values despite changes in that environment. Traditionally, control systems have utilised analog components; control systems which generate time-continuous outputs (voltage, pressure) to manipulate process inputs and which operate on continuous signals from instrumentation measuring process variables (position, temperature, light, volume, etc.). In the 1970's, the use of discrete or logical control elements, and the use of programmable logic controllers to automate machining, manufacturing, and production facilities became widespread. In parallel with these developments has been the accelerating use of digital computers in industrial and commercial application areas, both for logic-level control and for replacing analog control systems. The development of inexpensive microcomputers with arithmetic and logical capability, orders of magnitude beyond that obtainable with analog control elements, has resulted in the rapid substitution of conventional control systems - by digital, computer-based, programmable, highly reliable control systems.

Digital Controlled Camera (A/V)
Camera that uses microprocessor servo-controls to automate the alignment of the camera and ensure optimal, automatic performance under a variety of production conditions.

Digital Circuit (computer/microelectronics)
Circuit which operates in the manner of a switch; it is either "on" or "off". It is more accurately called a "binary circuit".

Digital Computer (computer)
Computer that processes data that has been converted into binary numbers. All common computers are digital (see analog computer).

Digital Counter (computer)
Instrument which, in its simplest form, provides an output that corresponds to the number of pulses applied to its input. The simple counter-type has a single count input (also called the clock input or pulse input), while the more complex counter-type has additional inputs that alter the count sequence. Digital counters include: geared mechanisms (tape counters, odometers), relays (old pinball machines and old telephone switching systems), vacuum tubes (old test equipment), and solid-state semiconductor circuits (most modern electronic counters).

Digital Data (communications, computer)
Data consisting of a sequence of discrete elements (for example, "0s" and "1s").

Digital Monitor (A/V, computer)
Screen (cathode ray tube) displaying digital, or TTL (transistor to transistor logic) signals from a computer. The majority of digital monitors use the same CRT technology found in a TV and must convert the digital signals to analog in order to illuminate the screen.

Digital Multiplication by Analog Convolution: DMAC (computer/photonics)
Algorithm for binary multiplication popularised in digital optical computer research.

Digital Optical Computer: DOC (computer/photonics)
Digital computer based on optical hardware; usually a general purpose computer, it is implemented by mimicking electronic logic devices, but utilising optical devices (light).

Digital Private Branch Exchange (communications)
Capability of a local or building network based on the private branch exchange (PBX) architecture. This digital switching system provides integrated voice and data switching capabilities. For now, the cost associated with a single, integrated, voice and data switch may exceed the cost of having a separate voice and a separate data switch.



Digital Signal Processing: DSP (communications, computer)
Term used to apply to the creation of electronic, acoustic effects such as reverberation, chorusing, flanging, panning. All synthesised sound involves Digital Signal Processing.

D197. Digital Sound (A/V, computer)
Method by which stereo sound and compact discs are recorded. Analog audio is converted to a string of binary numbers that represent pitch and loudness at any given movement. The numbers are recorded on audio, or video tape, or other media and are converted back to an analog sound signal for listening or analog reproduction.

Digital Still Store System (A/V, computer)
Term that is also called electronic still store system or ESS; it is an electronic device that can grab a single frame from any video source and store it in digital form on disk.

Digital Transmission (communications)
Term used for describing the transmission of digital data (as opposed to analog voice and/or video information), using either an analog or digital signal, in which the digital data is recovered and repeated at intermediate points to reduce signal degradation.

Digital Video Effects: DVE (A/V, computer)
Visual effects produced by electronic devices that convert traditional analog video signals into digital (binary, numerical) information.

Digital Video Tape Recorder: DVTR (A/V, computer)
Videotape recorder that receives digital, rather than analog information. The signals can be more easily manipulated for video enhancement and special effects (see D2).

Digital Voltmeter (computer)
Instrument for measuring potential difference and displaying the measurement directly in digital form. A wide variety of both alternating and direct current instruments exists capable of measuring from microvolts to kilovolts, at rates from a measurement per few seconds to over 1,000 measurements per second, with an accuracy from 99% to 99.995%.

Digitize (communications, computer)
Converting an image or signal into digital code for a computer. It includes scanning an image, tracing a picture on a graphics tablet, or converting camera images into a computer. 3-D objects (artifacts - models) can be digitised using a device which has a mechanical robotic arm moved around the object. Sound, temperature and movement are also digitised when converted to binary code.

Digitizer (computer)
Graphics device that converts images into digital data that a computer can manipulate.

Digitizing Tablet (computer)
Graphics input device that allows the user to create images. It has a special stylus that can be used to draw or trace images, which are then converted to digital data that can be processed by the computer.

Diminuendo (A/V, M/M, Windows)
Musical term for a gradual decrease in the volume of playing (also called decrescendo).


D207. Dimmer (A/V)
Device for control of light intensity by throttling the electric current flowing to the lamp.

D208. DIN (communications, computer)
Deutches Institute fur Normalization - an organization similar to ANSI that establishes standards for Germany. It has become the de facto standards bureau for Europe.

DIN Connector (communications, computer)
Connector standard for plugs and sockets (male & female connectors) for connecting devices such as keyboards, mouse devices, etc.

Dingbat (computer/printer)
Typographical term for a character that is not part of a standard character set. Dingbat characters include decorative symbols, icons, arrows, numbers in circles, and many others (also can be known as WingDings, and/or WebDings).

Diode (computer/microelectronics)
Device permitting current to flow in one direction only. Diodes are used in logic circuits to control the passage or non-passage of a signal from one element to another. It is made up of a two-terminal electron gate exhibiting a non-linear current-voltage characteristic. Some classifications of diodes are: capacitor diodes, constant-voltage diodes, light-emitting or light-sensitive diodes; negative-resistance diodes, rectifier diodes, etc.

Diode Gun (A/V)
Type of pickup tube in which the gun, or electrode array emitting and shaping the scanning beam, causes electrons to be focused at two points instead of three: the resulting smaller beam spot produces improved resolution.

Diode-Transistor Logic: DTL (computer/microelectronics)
Logic employing diodes with transistors used only as inverting amplifiers.

Diopter (A/V)
Adjustment on camera electronic viewfinders which compensates for the user's vision.

DIP: Dual In-Line Package (computer)
Common integrated circuit package used for microcomputer chip manufacturing. The carrier or casing within which the semiconductor integrated circuit is assembled and sealed. The package consists of a plastic or ceramic body with two rows of seven vertical leads which are inserted into a circuit board and secured by soldering.

DIP Switch (computer)
Toggle positions on a switch that is mounted on a microcomputer chip that is used to set the switch for different operating functions (see Dual In-line Package).

DIR (computer/DOS)
DIR command in DOS lists one or more files in a directory.

Direct Access (computer)
Immediate access to a record in secondary storage, usually on a disk.

Direct Access Method (computer)
Technique for accessing the location of information on a disk by determining a storage address location from a known, identifiable, key reference such as a name or number.

Direct Access Storage Device: DASD (computer)
Storage device in which a record can be accessed directly without calling on the CPU.

Direct Connect Modem (communications, computer)
Term used to describe a Modem connected directly to a telephone line.

Direct Conversion (computer)
Term used to describe a system conversion whereby the end users simply cease to use the older system and start to use the new system.

Direct Coupled Amplifier (computer, electronics)
Device used for amplifying signals with dc (direct current) components. There are many different situations where it is necessary to amplify signals having a frequency spectrum which extends to zero frequency. Some typical examples are amplifiers in electronic differential analysers, certain types of feedback control systems, and some medical instruments such as electrocardiographs. Amplifiers which have capacitor coupling between stages are not usable in these cases because the gain at zero frequency is zero. Therefore, a special form of amplifier, called a direct-coupled amplifier, is necessary. These amplifiers will also amplify ac (alternating current) signals.

Direct Current (computer, electronics)
Electric current which flows in one direction only, through a circuit or equipment. The associated direct voltages, in contrast to alternating voltages, are of unchanging polarity. Direct current corresponds to a drift or displacement of electric charge in one unvarying direction around the closed loop or loops of an electric circuit. Direct current and voltages may be of constant magnitude or may vary with time. Direct current power is generally obtained at the required device by the rectification of commercially available alternating current (ac) power, to direct current (dc) power. High-voltage dc transmission systems have been constructed throughout the world since the 1950s. Very large amounts of power, generated as ac and ultimately used as ac, are transmitted as dc power. Rectifiers supply the sending end of the dc link; inverters then supply the receiving-end ac power system from the link. High-voltage dc transmission is generally more economical than ac transmission when extremely long distances are involved.

Direct Current Circuit Theory (computer, electronics)
Analysis of relationships within a dc circuit. Any combination of dc voltage or current sources, such as generators and batteries, in conjunction with transmission lines, resistors, inductors, capacitors, and power converters, such as motors, is termed a dc circuit. Historically, the dc circuit was the first to be studied and analysed mathematically.

Direct Digital Colour Proof (computer/printing)

Proof made directly from digital data output by a desktop or high-end colour prepress system, without an intermediate film stage.

Direct File Organisation (computer)
Term used to describe an arrangement of records so each is individually accessible.

Direct File Processing (computer)
Processing that allows the end user to access a record directly by using a record key.

Directional (A/V, M/M, communications)
Term used in communications to describe a type of receiving and transmitting antenna. The term is also used in Audio/Visual to describe the capability of a microphone to reproduce sounds impinging on it from different directions. Microphones are classified as omnidirectional, bidirectional, unidirectional and cardioid (heart-shaped).

Direction Keys (computer/keyboard)
Four arrow keys on a computer keyboard. Each arrow key is named for the direction the key points: UP arrow, DOWN arrow, LEFT arrow, RIGHT arrow.

Directional Coupler (computer, electronics)
Waveguide circuit of four guide terminals (A,B,C,D) such that there is a complete isolation between A and C, and between B and D, but no isolation at all between the two terminals of any other combination. A common type of directional coupler is based on the interference of electrical waves. A directional coupler can be most useful in selectively measuring forward (incident) or backward (reflected) wave.

Directional Microphone (A/V)
Capability of a microphone to reproduce sounds impinging on it from different directions. Microphones are classified as omnidirectional, bidirectional, unidirectional and cardioid.

Directional Light (A/V)
Light that illuminates a relatively small area with a distinct light beam. Directional light, produced by spotlights, creates harsh, clearly defined shadows.

Direct Memory Access: DMA (computer)
Method of gaining direct access to main storage to achieve data transfer without involving the central processing unit (CPU).

Direct Narrative (A/V)
Voice-over scripting technique in which the text is related directly to the pictures (see Keying and Indirect Narrative).

Director (A/V)
Person who commands the studio and control room personnel during a production.

Directory: DIR (computer)
DOS Term for a command that lists the current listings (files, indexes) on a disk. A directory is a collection of files and subdirectories stored at the same location. The name of the directory identifies its location. Directory is part of the structure for organising files on a disk (see subdirectory).

Directory Hashing (communications, computer)
In Local Area Networking, file-server software that maps all directory files and can keep this information in Random Access Memory (RAM) for rapid response to workstations.



Directory List Box (computer, Windows)
Element of a file selection dialog box. This element selectively lists the subdirectories of the designated directory of a specified logical drive.

Directory Pane (computer/Windows)
One of the two directory views used by File Manager (the other is tree pane). A Directory Pane displays the file and subdirectory names of a given directory.

Directory Path (computer/DOS)
Directions to a directory or file within the computer memory. In the DOS commands, for example, C:\WINDOWS3\SCHED\JULY.CAL can be the path name of JULY.CAL file in the SCHED subdirectory within the WINDOWS3 directory on drive C.

Directory Replication (computer/Windows)
Copying of a master set of directories from a server (called an export server) to specified servers or workstations (import computers) in the same or other domains. Replication simplifies the task of maintaining identical sets of directories and files on multiple computers, because only a single master copy is maintained. Files are replicated when added to an exported directory and every time a change is saved to the file. The Directory Replicator Service replicates directories, and associated files.

Directory Tree (computer/Windows)
Graphic display of directory structure of a disk. They are shown as a branching structure that resembles a tree: as branches off the top-level directory, known as the root directory.

Directory Window (computer/Windows)
File Manager window that lists the contents of a directory. Each directory window shows all the files and other directories contained in the directory.

Disable (computer)
Turn off, discontinue or terminate a function (see enable).

Disabled User Account (computer/Windows)

User account that does not permit logons. The account appears in the user account list of the User Manager window and can be restored to enabled status at any time.

Discrete (computer/microelectronics)
Having an individual identity; fabricated prior to installation, and/or separately packaged.

Discrete Circuits (computer/microelectronics)
Electronic circuits built of separate, individually manufactured, tested, and assembled capacitors, diodes, resistors, transistors, and other specific electronic components.

Discrete Component (computer/microelectronics)
Circuit component having an individual identity such as a capacitor, resistor, or transistor.

Discrete Word System (computer)
Speech recognition system specifically limited to understanding isolated words.


Discriminator (communications, electronics)
Circuit that transforms a frequency-modulated or phase-modulated carrier into a wave that is amplitude-modulated as well as frequency-modulated. The amplitude modulation is then detected by a linear diode detector. Commonly used discriminators are the Foster-Seely discriminator and Ratio detector, which are popularly used in FM and TV receivers.

Dissolve (A/V)
Coordinated fading out of one picture from a screen and the fading in of another picture.

Disk Access Method (computer)
For Disk Access, indexed access methods are used to control records and files. The index may be a look-up table of contents for each file and/or record within a file. Sequential Access Methods are also used when retrieval of specific records is not required. ISAM (indexed sequential access method), combines both by providing an index that is maintained in sequential order. The fastest method is Direct Access. It uses a formula to convert fields such as phone number, account number, into a physical storage address.

Disk Access Time (computer)
Average time to position a read/write head over a designated point on the disk track.

DISKCOMP (computer/DOS)
Command in DOS compares two disks to see if they are the same except for different disk serial numbers and volume numbers that may have been assigned in Formatting.

Disk Configuration Information (computer/Windows)
Windows networking Registry includes information of the configuration of the system's disk(s); assigned drive letters, stripe sets, mirror sets, volume sets, stripe sets with parity.

Disk Controller (computer)
Device that controls the signals to and from the computer's disk drive(s).

DISKCOPY (computer)
DOS utility for making copies, and formatting in the process. It is used to make backup copies of floppy diskettes and archival copies of purchased software. To make a backup copy of a disk in drive A on another in drive B, enter: DISKCOPY A: B: /V. DOS will display a prompt to put the source disk in Drive A and the target disk in drive B. When the user presses any key, DOS will copy the diskette in drive A, formatting the disk in drive B, if necessary, to the same as the disk in drive A.

Disk Drive (computer)
Device that houses and controls the magnetic disks used for information storage.

Disk Drive Icon (computer/Windows)
Icon in File Manager that represents a disk drive. Different icons depict floppy disk drives, hard disk drives, network disk drives, RAM drives, and CD-ROM drives.

Disk Duplexing (computer/Windows)

Establishing a mirrored copy on a disk with a different controller.


Disk Format (computer)
Format for storage of information on a disk (floppy disks, hard drives, etc.)

Diskette (computer)
Small, removable disks used for computer memory storage (floppy disks).

Diskless Workstation (computer)
Computer terminal that does not have any local disk storage, but must rely on a centralized computer on a local or remote network for daily operations. A diskless workstation is similar to older terminals ("dumb tubes", "green screens") but that still has some local functions for screen, keyboard access, and local chip-based memory.

Disk Mirror (computer)
Redundant recording of information on duplicate disk, automatically, that is used in fault-tolerant systems where all of the information must be duplicated at all times. This leaves one disk as a backup if the other disk should fail.

Disk Organizer (computer)
Synonym for a disk defragment utility or application.

Disk Pack (computer)
Stacked array of disks in a removable housing that can be mounted in the computer memory unit, and also demounted and stored as archive or backup storage.

Disk Server (communications, computer)
In Local Area Networking, a hard disk used to share files with several users.

Disk Striping (computer/Windows)
Writing data in strips across a volume created from areas of free space: one from 2 to up to 32 disks.

Dispersion (computer/photonics)
Phenomenon of light waves; different frequencies of light propagate with different speeds in a medium, causing problems of pulse deformation in long distance fiber optic cabling.

Displayed Value (computer)
Term used to describe, in a spreadsheet cell, the calculated result of a formula or function.

Dissolve (A/V)
Gradual transition from camera shot to camera shot, in which the two images temporarily overlap. This effect is also called lap-dissolve, or lap.

Distortion (A/V, electronics)
In Audio terminology, unnatural alteration or deterioration of sound. In Video terminology, near objects look large, far objects look comparatively small. Generically, distortion implies any undesired change in the waveform of a signal passing through a circuit, including the transmission medium.

Distributed File Serving (communications, computer)
In Local Area Networking applications, distributed data processing to several computers rather than to one central computer.

Distributed Function Terminal Mode - DFT (communications, computer)
Emulation mode for allowing a terminal (i.e. 3270-type) to conduct a number of simultaneous or concurrent sessions with a mainframe or minicomputer.

Distributed Processing (computer)
Newer method of connecting computers together by a communications network, where an older, more traditional "MIS" Shop, may not be required. The term is loosely used to refer to any computers with communications between them. In true distributed processing, however, each computer system is chosen to handle its local workload, and the network has been designed to support the system as a whole. Contrast this with older centralised processing and decentralised processing.

Distribution Amplifier (A/V)
Term used to describe an active form of signal splitting that allows a single audio or video source to be connected to two or more audio or video components.

Dithering (A/V, computer, M/M)
In computer graphics, the creation of additional colours and shades from an existing palette. In monochrome displays, shades of greys are created by varying the density and patterns of the dots. In colour displays, colours and patterns are created by mixing and varying the dots of existing colours. Dithering is used to create a wide variety of patterns for use as backgrounds, fills, and shading, as well as for creating halftones for printing. Dithering can help shade and lighten edges to remove the appearance of "jaggies" (the stair-step effect caused from lower resolution of the edges of an object).

Divider (Frequency) (computer/microelectronics)
Counter added to provide an output pulse after receiving a special number of input pulses.

DLL (computer)
Dynamic Link Library - DLL is a file containing a collection of Windows functions designed to perform a specific class of operations. Functions within DLLs are called upon (invoked), as necessary by the applications, to perform the desired operations.

DMA: Direct Memory Access (computer)
Method of gaining direct access to main storage to achieve data transfer without involving the Central Processing Unit (CPU).

Document Window (computer/Windows)
Window within an application window. A document window has a document created or modified using an application. There can be more than one document window in an application window.

Documentation (computer)

Detailed written description of the programming cycle and specific facts about the program. The term is also used to describe the instruction manual for packaged software.

DOD Protocol Architecture (communications)
Communications protocol architecture that has evolved from the Department of Defence (U.S.A.) ARPANET project and DOD standardisation activities.



Dolby and Dolby Surround Sound (A/V)
Audio noise reduction system used to reduce noise on stereo linear-track audio. Surround Sound takes rear-channel information from signals, video tapes, and laser discs with Dolby encoded soundtracks (32 channel). At least 3 speakers are required.

Dolly (A/V)
Camera support that enables the camera to move in all directions. Also, to actually move the camera toward (dolly-in) or away from (dolly out or dolly back) the object.

Domain (communications, computer/Windows)

In Local Area Networks, a jurisdiction of servers and clients controlled and managed by a single server. In personal computing, system and peripherals the computer controls. In Windows Networking Advanced Server, a collection of computers that share a common domain database and security policy. Each domain has a unique name: Domain Name.

Domain Controller (computer/Windows)
For a Windows Networking Advanced Server domain, the server that authenticates domain logons and maintains the security policy and the master database for a domain.

Donor Atom (computer, electronics)
Impurity atom in a semiconductor which can donate one or more conduction electrons to the crystal by becoming ionized and positively charged. The ionization energy of a donor atom is the energy required to dis-associate the electron from the atom and put it in the conduction band of a crystal.

Donut (A/V)
Music, usually for a television commercial, beginning and ending with a vocal and having an instrumental underscore for narration in the middle.

Dopants (computer/microelectronics)
Selected impurities introduced into semiconductor substrates in controlled amounts, the atomic structure of which form negative (n-type) and positive (p-type) conductive regions. Phosphorus, arsenic, and antimony are n-type dopants for silicon: boron, aluminium, gallium, and indium are p-type dopants for silicon.

Doping (computer/microelectronics)
Addition of controlled impurities to a non-conductive material to achieve the desired semiconductor characteristic, accomplished through thermal diffusion or ion implantation.

DOS: Disk Operating System (computer/DOS)

Single user operating system developed by Microsoft Corporation, for personal computers.

DOS Command, in DOS, selects where DOS is loaded and whether the link to reserved memory is preserved after the booting (starting up the computer) process so that the user can use the available reserved memory for other applications and device drivers.




DOS=HIGH,UMB (computer/DOS)
This command loads DOS in reserved memory and retains the link to reserved memory so that the user can load other device drivers using DEVICEHIGH, or other programs using LOADHIGH. This command would be placed in the CONFIG.SYS file after the DEVICE=HIMEM.SYS and DEVICE=EMM386.EXE commands. As shown in the term, two parameters can be combined by separating them with a comma.

DOSKEY (computer/DOS)
DOSKEY command in DOS remembers executed DOS commands that the user can repeat, edit and use to create macros (memorised key stroke sequences). While DOSKEY is loaded, the user can use several keys to switch to a different command that DOSKEY remembers, or use several keys to alter the command displayed on the command prompt.

DOS Prompt (computer)
Prompt on a computer screen indicating the system is ready to accept commands from the user. Also, in DOS, the letter designation for the active disk drive. The prompt appears at the left side of the computer screen and is followed by a colon (example C:).

DOS Shell (computer)
Menu driven program in DOS (4, 5) for a menu of commands and functions activated by the keyboard or a mouse, rather than typing a command's character string each time.

Dot Area (computer/printing)
Proportion of a given area covered by halftone dots, usually expressed as a percentage.

Dot Etching (computer/printing)
Chemically changing dot size on halftone films, for localised or general colour correction.

Dot Gain (computer/printing)
Change in size of a printing dot from the film to the printed sheet, expressed as a percentage; an increase in dot size from 50% to 60% is called a 10% gain.

Dot Matrix (computer/printing)
Pattern of tiny dots that form character and graphic images on video screens and printers. Display screens use a matrix (set of rows and columns) of dots just like television sets. Impact printers use one or two columns of dot hammers that are moved across the paper. Laser printers "paint" dots of light a line at a time onto a photographic drum. The more dots per square inch, the higher the resolution.

Dots Per Inch: DPI (computer/printing)
Measure of the resolution or addressability of a display or output device.

Dot Pitch (computer/printing)
Resolution of a dot matrix. For display screens, it is expressed as the width of an individual dot; for example, newer multi-media screens have a .28 dot pitch which refers to a dot that is 28/100th of a millimeter in diameter. The smaller the number, the higher the resolution. For printers, it is expressed as the number of dots per linear inch; for example, a desktop laser printer prints at least 300 dpi or 600 dpi. The larger the number, the higher the resolution. In printing, it is the distance between adjacent dots in a halftone screen.


Double-Ganger (A/V, colloquial, CBC Broadcasting Corporation)
Term colloquially used to describe a specific, simply fabricated device used to interface an audio control unit from a microphone (speaker at a podium, for example) into an audio converter and balancer, so that the output sound can be heard through an acoustic coupler device to a telephone handset and the sound (event, speaker) can then be heard, without distortion, through the telephone system. The reverse capability, of hearing the telephone caller on the telephone line, through the acoustic coupler, then to the audio mixer, and then to a set of speakers, allows an audience to hear the telephone caller through the local speaker system. This process allows for interactive audio between a speaker/audience in one location with a person/audience at the other end of a telephone connection.

Double Click (computer/mouse)
Press a mouse button twice in quick succession (not moving the mouse between clicks).

Double Click Speed (computer/mouse)
Time interval within which two mouse clicks have to occur to be registered by the system as a double-click. A mouse "Control Panel" can be used to set the double-click speed.

Double Density Disk (computer)
Disk or Diskette with double the storage capacity of older, same size disks/diskettes.

Double Headset (A/V)
Telephone headset (earphones) that carries program sound in one earphone and the production control direction information in the other: also called split intercom.

Double-Muff Headset (A/V)
Special earphones used when working close to a high-volume sound source, such as a rock band, or crowd noises, to keep out the surrounding environmental sounds.

Double Reentry (A/V)
Complex switcher through which an effect can be fed back into the audio/video mix section, or the mix output into the effects section, for further effects manipulation.

Double Sided Disk (computer)
Disk or Diskette that can be recorded and read by the read/write head on both sides.

Double System (A/V)
Simultaneous recording of pictures and sound on two separate recording devices: the pictures on film or videotape and the sound on audiotape.

Downloadable Font (computer/printer)
Printer Font downloaded to printer memory from disk provided by a font manufacturer.

Down Link (communications)
Communications channel from a satellite to an earth station: also used to describe the actual antenna (dish) that receives the signals coming from the satellite in space.

D316. Download (communications, computer)
To transfer data from a central computer to a remote computer - or from a file server on a local area network to a workstation. It implies transmitting an entire file, rather than interacting back and forth in a conversational mode.

Downsizing (computer)
Recent term used to describe the conversion from mainframe and minicomputer centralised resources to distributed information systems utilising powerful personal computers and powerful Local Area Networks with File, Database, and Communications Servers at the central hub of a LAN acting as the coordination point for information storage access, retrieval and communications. Downsizing also includes the capability for individual users to access all system resources and to process information at the end-user workstations independent of any mainframe or minicomputer control.

Downstream Keyer (A/V)
Audio/Visual Switcher control that permits the technical director to key a title or other graphics over the signal at the line-out, as the signal leaves the switcher.

Downtime (A/V)
Period of time when equipment is not in use, usually meant to refer to broken or malfunctioning equipment on the "to be repaired" list. Downtime can also be used to describe planned equipment maintenance and service periods.

Downward Compatible (computer)
Older systems that can still operate the same software as newer computer systems, however, this rarely occurs since the strategy is to encourage new acquisitions (see upward compatible).

DPCM (communications, computer)
Differential Pulse Code Modulation - DPCM is the process used by 1-bit converters to encode and decode digital sound or video data based on the difference between successive samples rather than the actual value of the sample. DPCM has better sound quality for the same number of bits per sample, or enables digitised sound or video information to be stored in smaller files by compression techniques.

DPSK (communications)
Differential Phase Shift Keying is the common form of phase modulation used in modems. It does not require complex demodulation circuitry, and it is not susceptible to random phase changes in the transmitted waveform.

Drag (A/V, computer)
Move an object on screen where complete movement is visible from its starting location to its destination. The movement may be activated with stylus, mouse or keyboard. In Audio/Visual terminology, the friction needed in the camera mounting to allow smooth panning and tilting.

Drag-And-Drop (computer)
Windows process whereby an icon representing an object, such as a file, can be moved (dragged) by the mouse to another location, such as a different directory, and placed (dropped) in that location. Visual Basic provides Drag-and-drop for control objects.

DRAM (computer)
Dynamic Random Access Memory - integrated circuit devices that store data as the charge in a capacitor. DRAM must be continuously refreshed to restore the charge that would otherwise decay with time: commonly supplied in the form of multiple chips mounted on a small, printed circuit board in banks of 1, 2, 4, 8 Megabyte capacity (i.e. 1M x 8, 2M x8, 4M x8, etc).


DriveBar (computer/Windows)
Allows a user to change drives by selecting one of the drive icons.

Drive Icon (computer/Windows)
Icon in a directory window in File Manager that represents a disk drive on a computer system. Different icons depict floppy disk, hard disk, network, RAM, CD-ROM drives.

Drive List Box (computer/Windows)
Element of a file selection dialog box (usually a drop-down list box) that selects the logical drive for subsequent display of directory and file lists.

Driver (communications, computer/microelectronics)
Layer of software, conforming to an API (Applications Program Interface) that interfaces between LAN software and the hardware on the network card. Also, a Program with control instructions for devices such as printers, plotters, graphics programs, typestyles, etc. In microelectronic fabrication, an element coupled to the output stage of a circuit in order to increase its power or current handling capability or fanout; for example, a clock driver - to supply the current necessary for a clock line.

Drop (A/V)
Large, painted piece of canvas used for scenery backing.

Drop Down List Box (computer/Windows)
Single-line dialog box that opens to display a list of choices.

Drop Down Menu (computer/Windows)
Set of commands that drops down from a menu bar.

Drop Frame (A/V)
Form of SMPTE time code (Society of Motion Picture and Television Engineers) created to match clock time precisely. Two frames of code are dropped every minute on the minute, except the tenth minute, to correct for the fact that colour frames occur at a rate of 29.97 per second rather than an exact 30 frames per second.

Drop Lines/Cable (communications/cable TV)
Portion of a cable television distribution system that connects individual homes. Also used for telephone "drops", and cable "drops" on a Local Area Network (drops to the actual outlets).

Dropout (A/V)
Loss of part of the video signal, which shows up on the screen as white glitches: caused by uneven videotape iron-oxide coating (bad tape quality, or over-use, or dirt).

Dropout Compensator: DOC (A/V)
Term used to describe a circuit used in most video cassette recorders (VCRs) to hide dropouts. It operates by substituting a scan-line or segment of a previous frame for a missing scan-line or segment. It detects dropout (partial loss of video signal) and substitutes for missing information the information from the preceding scan line and is a feature offered on more sophisticated videotape recorders.

Drum Machine (A/V, computer, M/M)
Synonym for a percussion synthesiser. Drum machines have special features for percussionists, including small, rubber-covered pads that play drum sounds and an internal sequencer to store patterns and songs. Drum machines can be used as a source of MIDI synchronisation. They cause the melodic tracks of a composition to be played back at a rate established by the drum machine's tempo.

Drum Plotter (computer/plotter)
Graphics output device in which paper is rolled on a drum with a computer-controlled pen poised over the paper as it is rolling by the pen.

Drum Printer (computer/printer)
Printer consisting of a cylinder with embossed rows of characters on its surface. Each print position has a complete set of characters around the circumference of the drum.

Drum Scanner (computer/printing)
Colour scanner where the original hard copy is wrapped around a rotary scanning drum.

Drum Servo (A/V)
Mechanism of a video-recorder that automatically controls the speed of rotation of the head drums.

DRW (computer, Windows)
File extension for files created with Micrografx Designer, Draw Plus, and Windows Draw applications. DRW files are vector-based rather than bit-mapped images.

Dry (A/V)
Term used by audio engineers to describe sound freed from added effects, such as reverberation, and equalisation. The opposite of dry sound is wet sound.

Dry Plasma Etching (computer/microelectronics)
Burning a matrix onto a thin wafer with hot ion generation through a mask that is used to evaporate the wafer's silicon dioxide insulation layer; it substitutes for wet processing that uses acids and film (etching) for the same pattern carving.

DS/DD (computer)
Double Sided, Double Density diskettes (3.5 inch in size).

DS/HD (computer)
Double Sided, High Density diskettes (mini-floppy disks 3.5" size).

DSP (A/V, communications, computer)
Digital Signal Processing - this term is usually applied to the creation of electronic, acoustic effects such as reverberation, chorusing, flanging, and panning. The term is also used for specialized communications chips that process digitized voice and data.

DSR: Data Set Ready (communications, computer)
RS-232 signal sent from a modem to a terminal stating that it is able to accept data.

DSU/CSU (communications, computer)
Data Service Unit/Channel Service Unit is a device that connects an in-house line to an external digital circuit (T1, T3, etc.). The DSU converts data into the required format, while the CSU terminates the line, provides signal regeneration and remote testing.


DTE (communications, computer)
Data Terminating Equipment: communications devices that are the source or destination of signals on a network; typically a terminal or computer.

DTL: Diode-Transistor Logic (computer/microelectronics)
Logic employing diodes with transistors used only as inverting amplifiers.

DTP (computer)
Desktop Publishing - the process of creating material by combining word processing and graphic manipulation. It produces a file consisting of digital representations of images required to make lithographic plates. DTP implies the use of a page-oriented, graphic-manipulation application, but many word processing applications also provide DTP.

DTR: Data Terminal Ready (communications, computer)
RS-232 signal sent from a terminal to a modem stating it is able to accept data.

DTV (A/V, computer)
Desktop Video - the term describing the production of videotape presentations using the multimedia capabilities of personal computers. DTV implies the capability to edit video tapes by using the playback and record function of VCRs that can be computer controlled.

Dual In-Line Package: DIP (communications, computer)
Spider-like housing for chips with legs of pins on each side that are then inserted into sockets onto the computer printed circuit board. The Carrier or casing within which the integrated circuit is assembled or sealed, consists of a plastic or ceramic body with two rows of vertical leads which are inserted into a circuit board and secured by soldering.

Dual Redundancy (A/V)
Use of two identical microphones for the pickup of a sound source, whereby only one of them is turned on at any given time.

Dub (A/V)
Process of adding new sounds to an existing audio or videotape track from another sound source without erasing the existing track. Dubs can be made from tape to tape, or from record to tape: always one generation away from the recording used for dubbing.

Dubbing (A/V)
Copying of a tape or the adding of new information to a tape.

D359. Dubbing Down (A/V)
Dubbing (transfer) of picture and/or sound information from a larger videotape format to a smaller videotape format.

Dubbing Up (A/V)
Dubbing (transfer) of picture and/or sound information from a smaller videotape format to a larger videotape format.

Dumb Terminal (computer)
Display terminal without processing capability; dependent on the main computer for processing. A dumb terminal does not process data.

Dump (computer)
Printed representation of the raw content of a computer storage device, usually main memory, at a specified instant. By raw content it is meant that little or no interpretation is performed on the content; it is taken simply as a number of bit strings and presented to the reader, or end-user as such. Dumps may generally be classified as post-mortem dumps or snapshot dumps. The post-mortem dump, which occurs only when a program terminates (usually abnormally or prematurely), is the most primitive of debugging devices. Snapshot dumps are generally used for on-line debugging sessions that do not involve extensive dumps, nor are the snapshot dumps that are involved so bit-oriented, but the representations of memory contents that are produced share the snapshot dump's essential characteristic of being instantaneous descriptions of a dynamic environment.

Duplex Channel (communications)
Transmission of signals, simultaneously, in both directions at the same time.

Duplexed Drives (computer)
System fault tolerant technique in which virtually all hardware is duplicated, including disk controller, interface, and power supply.

DVI - Digital Video Interactive (computer)
Technology from Intel for compressing and decompressing data, audio, and full-motion video. On a CD ROM, it provides up to 72 minutes of full-screen video, 2.5 hours of half-screen video, 40,000 medium-resolution or 7,000 high-resolution images. It compresses full-motion video at ratios greater than 100 to 1 and still images at 10 to 1. DVI uses standard storage devices, but requires a DVI controller board in the personal computer. Developed by RCA's Sarnoff Research Labs, Intel acquired it in 1988. The compression rates now being experienced with new and more powerful Pentium-based computers is about 160 to 1. Microsoft adds DVI through its DVMCI extensions.

Dye (computer/printing)
Soluble colouring material, such as those used as colorants in colour photographs; as opposed to pigments, which are insoluble.

Dye Polymer Recording (computer, recording)
Optical recording using dyed plastic layers as the medium. A single dye polymer layer is used in WORM devices (Write Once, Read Many Times). Erasable optical disks, use a recording surface of two dyed plastic layers. The top layer is called the retention layer and the bottom layer is the expansion layer. A 1 bit (positive) is created (written) by shining a laser beam through the top retention layer and into the bottom expansion layer, which heats the area and causes it to expand into the retention layer to form a bump. The bumps in the retention layer are actual bits read by the unit (a cavity or "no bump", may generally be a zero or "negative"). To erase a bit, a laser with a different wavelength (frequency) is used to strike the retention layer; the bump then subsides or "smoothes out".

Dye Transfer (computer/printing)

Method of producing colour prints by making separation negatives, then transferring cyan, magenta, and yellow images from dyed matrices.

Dynamic Data Exchange (computer/Windows)
DDE is an Interprocess Communication (IPC) method used by Windows and OS/2 to transfer data between different applications.

Dynamic Link Library (computer/Windows)
DLL is a file containing a collection of Windows functions to perform a specific class of operations. Functions within DLLs are invoked as necessary by applications to perform the desired operations.

Dynamic Memory (computer)
Memory device which stores data as a charge on a capacity component and therefore needs refreshing (reading-out and reading-in) repetitively in order to preserve its contents.

Dynamic Microphone (A/V)
Microphone whose sound pickup device consists of a diaphragm that is attached to a movable coil. As the diaphragm vibrates with the air pressure from the sound, the coil moves within a magnetic field, generating an electrical current.

Dynamic RAM (computer)
Most common type of computer or chip memory. Dynamic RAM (DRAM) architecture usually uses one transistor and a capacitor to represent a bit. The capacitors must be energized hundreds of times per second in order to maintain the correct charges. Contrast with Static RAM, which is usually faster and does not require refresh circuitry. Unlike firmware chips (ROMs and PROMS, etc.) both varieties of RAM loose their content when the power is turned off. Static RAM is much faster than DRAM but it may be less efficient in terms of power consumption (power hungry).

Dynamic Range (computer/photonics)
Term used in optical computing to define the ratio of the highest usable intensity to the lowest usable intensity in an analog optical system. Higher intensities cause nonlinearity problems, while lower intensities become indistinguishable from noise.

D2 (A/V, computer)
Technology utilising electronic computing devices that can grab a minimum of six (6) frames either side of a master tape or from any video source and store, edit, retrieve, cut, colour control, all in digital format (digitized video). The results, for now, are re-processed and stored on 19mm (millimeter) digital video tape format, but other formats are being developed for future use (example, 8mm).