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  • a-Si (Amorphous Silicon)

    Based upon the electronic properties of a glassy alloy of silicon 
    and hydrogen, this semiconductor film is used as the active layer 
    in most AMLCDs.

  • Absolute Phase

    Correct polarity - (direction of energy) over two stereo channels.

  • AC

    Alternating Current - An electrical current that periodically reverses 
    direction. 
    The rate of change is known as frequency and is measured in 
    Hertz (Hz) sometimes referred to as, CPS - Cycles Per Second. 
    Standard electrical power wall sockets supply alternating current. 
    The UK system is 50Hz.

  • ACC

    Automatic Colour Control - Maintains constant colour (chroma) signal levels. 
    The burst signal is used as the ACC reference.

  • Acoustics

    The science of sound and sonic transmission.

  • Active Lines

    Video or Horizontal scanning lines that carry visible picture information 
    only as opposed to the blanking lines and vertical sync lines.

  • ADC

    Analogue-to-Digital Converter - Circuit that converts an analogue 
    (varying amplitude) signal to a digital (pulse type) signal.

  • Additive Primaries

    Red, Green & Blue are the primary colours of light from which all other 
    colours can be created.

  • Aerial

    Device used to send or receive electromagnetic waves through the air. 
    Referred to as Antenna in many other parts of the world including 
    Japan & America. 
    Quality TV aerials are important to receive quality signals and as such 
    quality picture images. This is even more paramount with 
    Digital transmissions.

    There is truth in the fact that the better the aerial the better the signal. 
    It must also be remembered that quality is only reproduced as good 
    as the weekest link - there are still many who tend to neglect their 
    aerial quality. 

  • AFC

    Automatic Frequency Control - Circuit that locks TV or FM receiver to 
    chosen station frequency.

  • AFT

    Automatic Fine Tuning - A circuit that compensates for a change in 
    frequency due to tuner oscillator drift.

  • AGC

    Automatic Gain Control - This maintains a constant video luminance level 
    by boosting weak (low light) picture signals electronically. In television it 
    minimises picture difference with changes in strength of incoming signal.

  • ALC

    Automatic Level Control - A circuit similar to AGC. Originally applied to 
    Nicam VCR's with hi-fi sound during the 80's, the ALC action varies the 
    gain to maintain a relatively constant output signal over the normal 
    range of sound levels. A system that continues in current day products.

  • Aliasing

    Visibly jagged steps along angled or objects edges, due to sharp tonal 
    contrasts between pixels.

  • Ambience

    Acoustic qualities of a room including background noise, echoes, reflections 
    and reverberations. Different acoustic qualities of rooms create a mass 
    variety of quality differences to the experience of sound performance.

    Rooms with furnishings such as carpets, curtains and upholstered furniture 
    are more likely to create a more acceptable ambience than a room with 
    wood flooring, no curtains and lack of soft furnishings.  

  • Amplifier

    An electronic device used to increase the strength of the current fed into it.

    This type of device is used for amplification of sound in audio & hi-fi terms 
    or amplification of signal strength connected to an aerial / antennae for 
    boosting TV picture or radio quality. 
    Sometimes amplification of signal is refered to as Gain.

  • Amplitude

    The strength of an audio or video signal measured in volts or decibels.

  • Analogue

    Any types of information which the human senses are able to recieve and to 
    interpret. 
    The world is an analogue world. During our whole everyday experiences 
    we all communicate via sound, speech and pictures which transmit 
    continious waveforms for our senses to translate. 
    Analogue was also the TV transmission format prior to Digital Switchover.

  • ANSI

    American National Standards Institute - Organisation responsible for 
    approving U.S. standards in many categories, including computers, 
    communications and presentation equipment. Such an ANSI standard 
    is internationally recognised in the table to measure brightness [lumens] 
    levels of equipment in the Audio/ Visual sector.

  • APC

    Automatic Phase Control - For stable colour signals by phase locking the 
    chroma process circuits.

  • Application

    Software that lets users do relatively complex tasks as well as create and 
    modify images or documents. 
    Common application types include presentation graphics' programs and 
    word processors.

    Current TVs have APPS similar to mobile phones.

  • ASCII

    American Standard Code for Information Interchange - National and 
    International standard character-to-number encoding widely used in 
    the computer and associated industries.

  • Aspect Ratio

    Ratio of image width to height commonly expressed as two whole numbers 
    (4:3 or 4-by-3), or sometimes in fractional numbers i.e., 1.33:1 (same as 4:3).
    The common denominator of 1 may also be implied following the first reference 
    so 1.33 is exactly the same as 1.33:1.
    By using the common denominator, comparisons are made easier. 
    The world's most popular Aspect Ratio of LCD & Plasma Televisions & 
    Computer monitors is now Widescreen, 16:9 ratio.
    Prior to this all screens were expressed as 4:3 or 4-by-3 or 1.33:1 or 1.33.
    Regarding today's WideScreen standard, a mentioned,  this has an 
    Aspect Ratio of 16:9 or 16-by-9 or 1.78:1 or 1.78.
    Launched by Philips in 2009 / 2010, there was an introduction of 22:9 ratio 
    TV screens that exacly reproduce Movies as they are filmed and portrayed in Cinemas.
     
    Alas, whilst an ideal viewing experience, the 22:9 system has not been adopted by 
    any other manufacturer. 

  • Aspect Ratio Accommodation

    The use of techniques used to interchange material prepared with an 
    Aspect Ratio different to the one it is to be presented in. 
    Example: A CinemaScope film broadcast on a  widescreen 16:9 or 
    conventional 4:3 ratio TV, requires more height and less width to 
    accommodate viewing pleasure.

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