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AAC (Advanced Audio Coding)

AAC is at the core of the MPEG-4 specifications and is the new audio codec of choice for internet, wireless and digital broadcast arenas. AAC provides a higher standard of audio quality then the older MP3 format.

ADSL (Asymmetric Digital Subscriber Line)

A way of receiving television, video and/or a broadband internet connection over a phone line. As well as broadband internet connections, it is increasingly being used as a platform for digital broadcast and other entertainment services such as "Video On Demand" all over an ordinary telephone line. This is sometimes called IPTV (internet protocol TV).

Aerial distribution amplifier

This allows you to divert your TV aerial signal to several rooms. You connect the aerial lead to the input socket and then run extension leads from the output. Because the signal is amplified it can be split without becoming weaker. If you want to split it just two ways, and have a strong signal from your rooftop aerial, you may not need to go to the expense of one of these. You could use a much cheaper Y splitter.

AFD (Active Format Descriptor)

Signal transmitted in UK Digital Terrestrial TV to ensure various types of letterbox picture are displayed to best effect on both 4x3 and 16x9 television sets.

AGARAS (Anti-Glare, Anti-Reflection, Anti-Static

glosAGARASA coating which actively suppresses reflected light.

Analogue

Analogue is the way our television is transmitted and recorded now. It is called analogue because the electrical signal voltages "represent" the picture and sound signals rather than being coded into a series of "l"s and "D"s, which is the way digital TV works.

Analogue signal

The broadcast signal which delivers just five TV channels* to your set via the aerial.*Not including other services and regional variations. Analogue TV channels broadcast in the UK and received via an aerial are BBC One, BBC Two, ITV1, Channel 4 and Five.

Aspect ratio

This defines the shape of a TV screen and is the relationship between the width and height of the screen. A traditional TV set has an aspect ratio of 4:3. A widescreen set has an aspect ratio of 16:9, giving a 'letterbox' shape like that of a cinema screen. The programmes on most of the major TV channels are now broadcast in 16:9 format.

Astra

The main satellites for UK and European reception. Astra 1A-1K orbit the Earth at 19.2 degrees East, and supply hundreds of foreign digital channels. Astra 2A- 2D orbit at 28.2 degrees East providing Sky Digital signals.

ATM (Asynchronous Transfer Mode)

ATM is a method for splitting digital audio, video or data signals into little data packets, which can all be fed together into large bitstreams, and with luck, reach their right addresses and can be put back together in the right order.

Attenuator

A passive device that weakens a signal that passes through it. The amount by which the signal power is reduced is usually expressed in decibels.

Audio description

Audio description is an additional narration that fits between dialogue in TV programmes and describes what is happening on-screen for those who have difficulty seeing. For example, it covers action sequences, body language, facial expression, costume and scenery.

Audio Picture Size Adjustment

TV automatically adjusts to the proportions of the broadcast image signal to fit your screen size.

Auto Install

Automatically tunes your TV and sets up the channels at the touch of a button.

Auto-Seeking RF Output

Automatically finds a free channel for the RF signal that has no interference, ensuring the best available reception.

AV (Audio-Visual)

Button on remote controls that switches the TV's input to the SCART socket.

AVL (Automatic Volume Leveller)

Minimises sudden changes in TV volume when commercials are transmitted.

Azimuth

The horizontal angle between an antenna's reception path and a compass direction. Usually expressed as a compass bearing or degrees East or West of South.