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 RadioShack Consumer Electronics Glossary: D

d-: see deci- (d-).
 
da-: see deka- (da-).
 
DA: see Distribution Amplifier
 
DAC
Acronym: Digital To Analog Converter
DIY: A circuit that takes digital input and converts it into analog output.
 
DAM
Acronym: Digital Automatic Music
Audio: Refers to compact discs containing songs in both MP3 and standard CD audio format.
 
D-AMPS
Acronym: Digital Advanced Mobile Phone Service
Telephony: A term used for digital cellular radio in North America.
 
DAO
Acronym: Disc At Once
Audio: A method of recording to CD in which the disc is written all at once without interruption and without the recording laser turning off. It is generally considered the best method for recording a CD. DAO also allows you to record separate tracks onto CD without the 2 second gap between each track (compare to TAO).
 
Dark Current or Dark Noise
Digital Video: The charge accumulated by pixels while not exposed to light. Normally, this charge is reduced or eliminated prior to capturing a picture.
 
Darlington Pair
Electronics: An amplifier consisting of two bipolar junction transistors with their collectors connected together and the emitter of one connected to the base of the other. A darlington pair circuit is characterized by both high current gain and high input impedance.
 
DAT
Acronym: Digital Audio Tape
Audio: An digital recording media format designed to allow music to be digitally stored onto magnetic cassette tape.
 
dB: see Decibel.
 
DBS
Acronym: Digital Broadcast System
Satellite: A digitally-transmitted direct satellite television broadcast.
 
DB-25
Computers: A 25-pin D-shell connector. This is the standard connector used for serial connections.
 
DB-9
Computers: A 9-pin D-shell connector. This is a smaller version of the DB-25 connector and is also used for serial connections.
 
DC
Acronym: Direct Current
DIY, Electronics: An electrical current that flows in one direction only, as opposed to alternating current (AC), in which the current flow alternates direction in a regular manner.
 
DCC
Acronym: Digital Compact Cassette
Audio: A digital recording media format developed by Philips and Matsushita in the 1990's. It has been replaced in the home market by CD-R and CD-RW.
 
DCS
Acronym: Digital Cordless Standard
Telephony: A cellular telephone system used in Europe.
 
DCS-1800
Telephony: A low-power variant of GSM with a 1.8 GHz carrier wave, used in Europe.
 
DCS-1900
Telephony: A proposed usage for GSM with a 1.9 MHz carrier wave, for PCS applications.
 
deci- (d-)
Measurement: SI / Metric unit of decimal measurement, equal to 10-1 or 0.1.
 
Decibel (dB)
Measurement: One tenth of a bel, a unit used to compare the ratio of two quantities (such as sound pressure, power, or intensity), or to express the ratio of one such quantity to an appropriate reference. The chart below shows decibel ratings along with common examples of sounds of that level.
Decibel Level Sound
0 dB Threshold of hearing
10 dB Breathing
Hearing testing booth
20 dB Isolated broadcast studio
Rustling leaves
25 dB Whispering
30 dB Library
Soft whisper
Quiet rural area at night
40 dB Quiet suburban area at night
Refrigerator  
50 dB Average home
Light traffic
Normal conversation  
55 dB Quiet suburban area in daytime
60 dB Clothes dryer,
Conversation in restaurant
Busy office
Background music
Typical urban area
65 dB Dishwasher
Washing Machine
70 dB Car
Electric sewing machine
Mixer
Noisy restaurant
On sidewalk by passing automobiles
Vacuum cleaner
75 dB Busy traffic
80 dB Alarm clock
Blow dryer
Garbage disposal
Freight train
Mini-bike
Office Tabulator
Outboard motor
Passing Snowmobile
Decibel Level Sound
85 dB Average Factory
Electric razor
90 dB Busy urban street
Diesel truck
Food blender
Lawn mower
On sidewalk by passing heavy truck or bus
Passing motorcycle
Roar of crowd at sporting event
Screaming child
Convertible ride on freeway
100 dB Boiler shop
Diesel truck
Garbage truck
Jackhammer
Jet takeoff (300 Meters)
Outboard motor
Farm tractor
On platform by passing subway train
Power tools
Woodworking shop
102 dB Leaf blower 
105 dB Helicopter
110 dB Inboard motorboat
Sandblasting
Snowmobile drvrs seat
Steel mill
Riveting
Auto horn
Stereo headset
115 dB Subway train screech
120 dB Auto horn
Propeller aircraft
Rock concert
Thunderclap
Chain Saw
 
Decoder
Video: A device that is connected between a video source (satellite receiver or cable TV line) and the television, enabling the user to decode scrambled signals. The decoder is built into DTH satellite antennas.
Audio: A decoder converts an MP3 file into audio or another format (such as WAV) before playing as audio.
 
Decompression
Computers: The process of restoring the contents of a compressed file.
 
DECT
Acronym: Digital European Cordless Telephone
Telephony: A digital cordless telephone standard used in Europe that incorporates some of the features of the cellular telephone systems. DECT telephones use picocells, and calls can be handed off from one cell to the next.
 
Deep Discharge
Batteries: Discharging a battery to a specific cut-off voltage at a low current rate. Discharge cut-off voltage is generally considered to be 0.5 volts.
 
DEH-15
Computers: The connector type for VGA monitor connections.
 
deka- (da-)
Measurement: SI / Metric unit of decimal measurement, equal to 10.
 
Demodulation
Communications: The process of recovering a signal from a modulated carrier so that it has substantially the same characteristics as the original signal.
 
Depth of Field
Digital Video: The distance between the nearest and farthest points that appear in acceptably sharp focus in a photograph (digital or analog). Depth of field varies with lens aperture, focal length, and camera-to-subject distance.
 
Depth Penetration
Metal Detectors: The greatest measure of a metal detector's ability to transmit an electromagnetic field into the soil matrix and produce a target signal.
 
Detection Pattern
Metal Detectors: The densest or strongest region of the search coil's electromagnetic field where detection occurs. It is balloon-shaped and changes in size in direct proportion to the target surface area.
 
Detuning
Metal Detectors: Adjusting the audio threshold into the null or less-sensitive tuning zone. It is also a method of narrowing a target's signal width manually for precise pinpointing. This is accomplished by returning to audio threshold over the target response area.
 
Device
Plug 'n Power: Appliances that can be plugged into modules that control the appliance when an X-10 signal is received from a controller.
Dew
Weather: condensation in the form of small water drops that forms on grass and other small objects near the ground when the temperature has fallen to the dew point, generally during the nighttime hours.
 
Dew Point
Weather: The temperature to which air must be cooled at a constant pressure to become saturated.
 
Diac
Electronics: A bidirectional thyristor that has two terminals and uses a symmetrical switching mode.
 
Dielectric
DIY, Electronics: The insulating material between the conductive plates of a capacitor.
 
Dielectric Constant
Electronics: The property of a material that determines how much electrostatic energy can be stored per a given volume when a given voltage is applied.
 
Dielectric Strength
Electronics: The maximum voltage an insulating material can withstand without breaking down.
 
Dighole
Metal Detectors: An indention left by previous hunters.
 
Digital
A system that uses bits to represent variables and store information, as compared to analog, which uses physical change to represent variables.
Audio: Digital recordings represent sounds that have been converted into groups of electronic bits, or zeroes and ones, and stored on a magnetic medium; those groups of bits are then read electronically. In the case of a CD player, the bits are read by a laser beam. Conversely, with analog technology, the grooves on a vinyl record are read physically by a needle. Because digital data are represented numerically, they can be copied repeatedly and each succeeding generation of copies is identical to the original. See Analog.
 
Digital Advanced Mobile Telephone Service: see D-AMPS.
 
Digital Modulation: see Modulation, Digital.
 
Diaphragm
Digital Video: The adjustable aperture that controls the amount of light passing into the camera. The diaphragm may be in front of, within or behind the lens.
 
Digital Audio
Audio: An audio signal from a digital source (DTV broadcast, DVD, CD Player, Satellite Receiver) that is carried by either a digital coax cable or an optical cable.
 
Digital Coax
Audio: A coaxial cable specifically designed to carry a digital audio signal.
 
Digital Video
Video: A video signal in a digital format (DTV, SDTV or HDTV), that is normally carried on component video cables for the highest video quality, although other outputs (such as for analog video) may be available.
 
Digital Zoom: see Zoom, Digital.
 
Digitization
Electronics, Computers: The process of converting analog information into a digital format.
 
Dimmer
Plug 'n Power: A type of module used for incandescent lighting appliances only. They respond to the commands Dim and Bright as well as ON and OFF. 
 
DIN Connector
Analog: Deutsches Insitut für Normung eV (German)
Electronics: A round, multi-pin connector that conforms to the standards set by Deutsches Insitut für Normung eV, a German organization responsible for setting standards. See the DIN Connector FAQ.
 
Diode
DIY, Electronics: A polarized semiconductor component (having a negative and positive electrode) that is designed to conduct electricity in only one direction.
 
Diode Logic: see DL.
 
Diode, Schottky
Electronics: A high-speed diode that has very little junction capacitance. Also known as a Hot-carrier Diode or Surface-barrier Diode.
 
Diode, Surface-barrier: see Diode, Schottky.
 
Diode-Transistor Logic: see DTL.
 
Diode, Zener
Electronics: A semiconductor diode in which the reverse breakdown voltage current causes the diode to develop a constant voltage. Used as a clamp for voltage regulation.
 
Diopter Correction
Digital Video: An adjustment on the viewfinder of a camera, allowing the user to adjust the viewfinder for near-sighted or far-sighted vision so that he or she does not need to wear glasses to use the camera.
 
DIP
Acronym: Dual In-line Package
Electronics: An integrated circuit package that has two rows of connecting pins.
 
Dipole
Audio, Video, Communications: A dual-rod antenna, usually found as a back-of-set or on-set antenna.
 
Diplexer
Video, Communications: A device used to combine two different signals (such as from a broadcast antenna and from a satellite system or cable television service) onto a single cable so that they can be split back into the individual signals for connection at the video equipment.
 
Direct Current: see DC.
 
Directional
Operating in a particular direction.
Audio, Video, Communications: Refers to antennas that are designed to receive signals along a line forward from the antenna. Also called Unidirectional. Compare to Bidirectional and Omnidirectional.
 
Direct Vision
Digital Video: Refers to cameras that use an optical viewfinder.
 
Discharge Curve
Batteries: A plot of voltage against time, at a given current drain and temperature. Generally speaking, primary batteries have sloping discharge curves and secondary batteries have flat curves.
 
Discharge Rate
Batteries: The current at which a battery is discharged.
 
Discone
Communications: An antenna that has the horizontal elements connected to the shield and the cone connected to the coax cable's center conductor, so that the actual configuration is an upside-down half-bow-tie
 
Discrimination
Metal Detectors: Adjustable circuitry which ignores or nulls audio responses from a specific conductivity range allowing positive responses to be heard from metals higher in conductivity above the discriminate control setting. Designed primarily to eliminate audio response from unwanted metals.
 
Discriminator, Mineral Free
Metal Detectors: A detector that can reject or ignore trash metals while simultaneously eliminating or balancing the effect of mineralized ground.
 
Discriminator, Motion
Metal Detectors: A detector type that requires search coil motion to activate its simultaneous ground balance and discriminate functions. See also Mineral-Free Discriminator and VLF/TR.
 
Dish
Satellite: The flat part of the satellite antenna that reflects the signal to the LNB.
 
Dish Network®
Satellite: A DTH (Direct-To-Home) satellite system service provider. The "Dish" in "Dish Network" is an acronym for "Digital Sky Highway".
 
Dispatch Calls
Communications: Standard mobile-to-mobile or mobile-to-base calls that do not use the Public Switch Telephone Network (PSTN).
 
Distortion
Audio: Unwanted audio signals that alter an input signal. Distortion is caused by a variety of factors.
Digital Video: A defect in an digital image, such as barreling and pincushioning, caused by a flaw in the lens.
 
(diT/dt)cr
Measurement: Critical rate of rise of on-state current.
 
DL
Acronym: Diode Logic
Electronics: A logic gate that uses diodes to perform AND and OR logic functions.
 
DMCA
Acronym: Digital Millennium Copyright Act
An act signed in 1998 for the purpose of updating the copyright laws of the United States.
 
DMM
Acronym: Digital MultiMeter
DIY: A multimeter with a digital display.
DNS
Acronym: Distant Network Service
Satellite: A service that allows the user to use a DTH (Direct-To-Home) satellite system in either a recreational vehicle or a commercial truck.
Dolby® Digital
Audio: A digital coding method using AC-3® coding to convey one or more audio channels, generally at a bit rate of 384 kbps.
 
Dolby® Stereo
Audio: An audio coding method used to convey surround sound over three speakers. Called Dolby® Surround in the consumer market.
 
Dolby® Surround: see Dolby Stereo®.
 
Dolby® Pro Logic®
Audio: A type of improved decoder used to decode Dolby Surround® content, using four speakers.
 
Dome
Audio: A dome-shaped cone.
 
Doppler Shift
GPS: A change in the wavelength (frequency) of energy in the form of waves.
 
Double Blip
Metal Detectors: A signal characteristic common to elongated ferrous targets such as nails or coins lying close to the surface detected in the All Metal no-motion mode.
 
Double D: see Scan, Wide.
 
Downlink
Satellite: Data being sent from a satellite down to an earth station.
 
Download
Computers: 1) To transfer data from a device to a computer using a direct connection.
 
DPDT
Acronym: Double Pole Double Throw
Electronics: A six-terminal switch or relay that can handle two separate circuits. Essentially, two SPDT switches or relays combined into a single component.
 
DPI
Acronym: Dots Per Inch
Computers, Digital Video: A measurement value used to describe the resolution of a display screen or the output resolution of a printer.
 
DPOF
Acronym: Digital Print Order Format
Digital Video: A format that allows you to embed printing information on a memory card.
 
DPST
Acronym: Double Pole Single Throw
Electronics: A four-terminal switch or relay that can open or close two separate circuits. Essentially, two SPST switches or relays combined into a single component.
 
Drain
The element in a field-effect transistor that is comparable to the collector in a bipolar transistor.
 
DRAM
Acronym: Dynamic Random Access Memory
Computers: Temporary memory that is lost when the power is turned off.
 
DRAM Buffer
Acronym: Dynamic Random Access Memory Buffer
Digital Video: Fixed memory used for image processing before the image is stored. Cameras with a burst mode have much larger DRAM buffers.
 
Drift
Metal Detectors: A loss of threshold tuning stability caused by temperature change, battery condition, mineral content, and/or detector design.
 
Driver
Audio: see Speaker Driver.
Computers: The program that allows a piece of hardware to work with a particular computer or operating system.
 
Drizzle
Weather: A very light, misting precipitation.
 
Drizzle, Freezing
Weather: drizzle, falling as a liquid, but freezing on impact with the colder ground or other exposed surfaces. It is reported as "fzdz" in an observation and on the metar.
 
DRM
Acronym: Digital Rights Management
Audio: The term for the various methods of tracking the sale and distribution of digital music.
 
Dry Bulb Thermometer: see Thermometer, Dry Bulb.
 
Dry Cell: see Cell, Dry.
 
D-Shell Connector
Electronics, Computers: A connector type primarily used in computers. The most common types are the DA-15, DB-25, DC-37, DD-50, DE-9, and DEH-15 connectors. The "D" refers to the shape of the connector, the following letter or letters refer to the connector size, and the number refers to the number of pins.
 
DSD
Acronym: Direct Stream Digital
Audio: The recording technology used in SACD. DSD promises better sonic performance as the encoded bitstream somewhat resembles the analog characteristics of the original analog signal.
  DSD PCM
Used in standard CDs Super Audio CDs (SACD)
Sampling 44.1 kHz / 16-bit 1-bit
Samples per second 44,100 2.82 million
 
DSL
Acronym: Digital Subscriber Line
Internet: A technology that allows high-speed Internet connections on standard telephone lines (POTS). The primary types of DSL are ADSL (Asymmetric Digital Subscriber Line) and SDSL (Symmetric Digital Subscriber Line).
 
DSP
Acronym: Digital Signal Processing or Digital Signal Processor
Audio: The method of manipulating analog information that has been converted into a digital form, or a component that is used for this purpose.
 
DTH
Acronym: Direct To Home
Satellite: Refers to home-based satellite systems.
 
DTL
Acronym: Diode-Transistor Logic
Electronics: A logic gate that uses diodes to perform AND and OR logic functions and then uses a transistor as an amplifier on the resulting signal.
 
DTMF
Acronym: Dual Tone Multi-Frequency
Telephony: The signal encoding used for dialed numbers, using two tones out of a group of eight. DTMF is the method used by touch-tone telephones, as opposed to the original pulse method, used by rotary telephones.
 
DTS™ Digital Surround
Acronym: Digital Theater Systems
Audio: A digital coding method used to convey one or more audio channels.
 
DTV
Acronym: Digital TeleVision
Video: A television standard that consists of High-definition Digital Television (HDTV) and Standard-definition Digital Television (SDTV).
 
Dual-conversion
Communications: A scanner reception method that uses a circuit with two stages and two intermediate frequencies to extract the data signal from the carrier.
 
Dual In-line Package: see DIP.
 
DV
Acronym: Digital Video
Digital Photography: Used to describe digital camcorders and digital camcorder tapes.
 
DVD
Acronym: Currently, DVD is not considered to be an acronym. Previously, it was an acronym for "Digital Versatile Disc"; and originally, it was an acronym for "Digital Video Disc".
Video: A video format that uses optical discs to store audio and video information. The parameters for DVD video are given below:
Parameter NTSC PAL
Frame Size: 720 x 480 720 x 576
Frame Rate: 29.97 frames/second 25 frames/second
Video Data Rate: 4~8 Mbps CBR or VBR (Constant/Variable Bit Rate)
Audio Settings: Stereo, 48 kHz and 192~384 kbps MPEG audio
 
DVD-Audio
Audio, Video: A format for high-resolution audio and multi-channel music. It is based on the DVD format, but contains only audio information.
 
(dvD/dt)cr
Measurement: Critical rate of rise of off-state voltage.
 
DX
Acronym: Distant X (transmitter or transmission)
Communications: Used to describe a long-distance transmission, generally from a foreign country. "DXing" is the hobby of seeking out and listening to these transmissions.
 
Dye Sub
Acronym: Thermal Dye Sublimation
Computers: A printing process where the ink is thermally transferred to printing media. Dye sub is generally more expensive than other methods; however, it provides extremely high quality. Additional cost is incurred because dye sub printers require special paper.
 
Dynamic Range
Digital Video: The measurement (in bits) of the accuracy of an image in color or gray level. A higher dynamic range results in finer gradations being preserved.
 
Dyne
Measurement: Cgs unit for force; equal to (g * cm * sec-2).

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