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  • Definition

    A reference made to the degree or sharpness of a video signal.

  • DisplayPort?

    DisplayPort™1.1

  • Dolby Pro-Logic

    Most suitable for movie viewing in the home, this is a variation of Dolby 
    surround utilising a greater configuration of sound channels to increase 
    depth. Usual configuration of speakers is three at the front 
    (left, centre and right) plus two or more at the rear [left and right with 
    inclusion of sub-woofer].

  • Dark Clip

    An adjustable circuit that limits the overshoots created by signal 
    re-emphasis. If uncorrected, they cause excessive frequency 
    swings of the FM luminance record signal.

  • DAT

    Digital Audio Tape - Used for professional, broadcast quality recording 
    and also the most common type of tape back-up for computers.

  • DBS

    Direct Broadcast Satellite - A system of transmitting TV or radio 
    programming from satellite to an end users' / viewer's receiving 
    dish which has is an LNB (Low Noise Block) to convert the 
    captured signal into picture and/or sound.

  • DC

    Direct Current - Electrical current that flows in one direction, including 
    battery power. Electrical AC (Alternating Current) transformers are used 
    in many devices to convert AC to DC.

  • DC Restoration

    The percentage measurement that refers to a plasma screen's or 
    television's ability to reach 0 volts DC level of blanking during the 
    transmission of a video signal. The higher the percentage of DC 
    Restoration, the better the plasma screen or TV at producing 
    dark scenes [black] with detail in most ambient light levels.

  • Deflection Yoke

    An electromagnetic device inside a CRT of a conventional television. 
    Made of copper wire it directs or aims the electron beam as it passes 
    through the picture tube.

  • Degausser

    Device that demagnetises the CRT [Cathode Ray Tube] colour 
    picture-tube for purity. Magnetism of the tube (a distortion or 
    merge of colours) can occur when electrical appliances with 
    motors are switched on and off in very close proximity to the 
    CRT screen, i.e., vacuum cleaners.

  • Deviation

    A term used to describe the amount of FM carrier swing caused by 
    luminance modulation.

  • Dichroic Lens

    Although the word 'Dichroic' means having two colours, this refers to a 
    special coating to the lens of the green gun of a large screen 
    conventional TV to filter to filter out unwanted colours in the 
    green spectrum.

  • Digital

    Data or voltages consisting of discrete steps or levels as opposed to 
    continuously variable analogue data.

  • Digital Memory

    Electronic trick circuit that allows a plasma screen or TV to recall a 
    stored still picture and display it simultaneously with one or more 
    additional pictures.

  • Diode

    A two-electrode semiconductor device used in circuits for converting 
    AC to DC.

  • Dipole

    Simple antennae / aerial consisting of just two straight rods separated 
    by a small distance.

  • Directional Antennae

    A TV or FM antennae / aerial that picks up signals better from one 
    focused direction more effectively than in others. Usually has two 
    or more sections or elements for increasing directivity and sensitivity.

  • Direct View

    Plasma screen or conventional type of TV set as opposed to projection 
    TV or DLP projected image.

  • Display Modes

    Varying display systems capable of producing different levels of 
    screen quality. This also refers to Resolution

    • CGA (Colour Graphics Adapter)
    • EGA (Enhanced Graphics Adapter)
    • VGA (Video Graphics Array)
    • XGA (Extra Graphics Array)

  • DLP*

    Digital Light Processing is a system used by many major manufacturers 
    of commercial and home cinema projectors. Producing a high quality 
    image in both domestic and commercial products this type of media 
    allows a much larger image projection.

    *DLP is a Trade Mark of Texas Instruments

  • Dot Crawl

    Caused by the interaction between chrominance (colour) and luminance 
    (brightness) portions of signals, this is a basic form of distortion seen on 
    PAL transmissions. Most noticeable in areas of high contrast 
    (usually Black & white borders), the effect is usually visible as crawling 
    dots on vertical boundaries between areas of colour.
    The use of comb filters or by using S-Video can reduce the effect.

  • DPI

    Dots Per Inch - Refers to the number of dots in a one inch line to measure 
    the resolution of a plasma screen or TV. The more dots per inch the 
    higher the resolution.

  • DV

    Digital Video Format that produces versatility and enhanced picture quality 
    utilised in commercial and home camcorders / recorders.

  • DTV

    Digital Television - Format that produces enhanced picture quality and 
    sound, replacing analogue television broadcasts.
    Final 'switchover' completed fully in the UK during 2013.

    Format allows the transmission of HDTV and 3DTV. 

  • DVD

    Digital Versatile Disc - Originally launched in Europe during the summer of 
    1997, this high capacity audio and video medium is capable of storing a 
    massive 4.7Mb of digital data. 
    Designed as a playback format for home cinema and commercial 
    presentations, recording can also be possible.

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