Analogue
The traditional way of broadcasting television and radio. An analogue signal directly represents the pictures and sound, whereas a digital signal codes the pictures and sound into 'computerised' data.

Analogue radio
FM and AM (medium, long and short wave) radio.

Analogue TV
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.

Attenuator
An electronic device that reduces the power of a signal.

Audio description
A spoken commentary on TV that describes what is happening on screen, particularly useful for visually impaired viewers. The commentary fits in between dialogue and describes action sequences, facial expressions, costume, scenery and so on.

Bandwidth
The range of frequencies used for transmitting a signal (think of it as the amount of space on the airwaves required to carry programmes). Digital broadcasting makes much better use of the bandwidth than analogue.

Broadband
Refers to a system or circuit that can carry signals over a wide range of frequencies or bandwidth. The wider the bandwidth, the more information that can be carried. A broadband internet connection gives you high-speed downloading of video and audio, etc.

CA
Conditional access: refers to channels that you need a viewing card to be able to watch.

CRT
Cathode ray tube, as in the traditional type of large-bodied TV set.

DAB
Digital Audio Broadcasting: the transmission system used for digital radio.

DCab, D-CAB
Digital cable: digital TV received via a cable connection.

Decoder
A device that unscrambles digital signals and turns them back into sound and pictures. It may come in a set-top box, or be built into a TV set or PVR.

Digibox
Informal way of referring to a digital set-top box.

Digital
The new way of broadcasting television and radio. A digital signal codes the pictures and sounds into 'computerised' data. The signal then has to be turned back into pictures and sounds by a decoder.

Digital can also refer to the way radio station frequencies are displayed as numbers on an FM/AM radio. This is not the same as DAB digital radio.

Digital switchover
The process of switching from analogue to digital broadcasting. In the UK this is happening in television between 2008 and 2012.

Digital terrestrial television (DTT)
Digital TV that is received via a standard aerial, e.g. as provided in the UK mainly by Freeview.

DLP
Digital light processing: a technology used in rear-projection flat-panel TV screens.

DOG
Digital on-screen graphic: a channel identification logo, usually seen in the top left-hand corner of the TV screen.

Downlink
A signal sent down from a satellite to the ground.

DSat, D-SAT
Digital satellite: digital TV received via a satellite dish.

DTT
Digital terrestrial television: digital TV that is received via a standard aerial, e.g. as provided in the UK mainly by Freeview.

DTV
Digital television.

DVB
Digital Video Broadcasting, a worldwide standard for digital TV technology.

DVD
Digital versatile disc (originally digital video disc): DVDs give far better picture and sound quality than a video cassette, and can store more than CDs. They can be used in DVD players and recorders and also in computers, though there are different, often incompatible formats.

DVI
Digital visual interface: a digital connection for high-quality video, suitable for high-definition TV.

DVR
Digital video recorder: more often known as a PVR (personal video recorder), this records TV programmes digitally on to a hard disk (like saving information on a computer).

Encrypted
Scrambled, as in programmes or channels that you need a viewing card to be able to watch.

Ensemble
A digital radio term for a single frequency that contains a number of radio channels. See also Multiplex.

EPG
Electronic programme guide: software built into a set-top box that gives on-screen listings of what's on TV now and for a number of days or weeks ahead. You can use the EPG to go straight to a programme you want to watch or to select something to record.

Freesat
Free satellite TV: programmes or services that you don't need to pay a subscription to receive.

Free to air (FTA)
A programme or service that you don't need to pay a subscription to receive.

Free to view
A programme or service that you don't need to pay a subscription to receive, though you may need a viewing card.

Freeview
The main UK digital terrestrial television service, which you receive via an aerial. No subscription is required.

Hard disk (or hard drive)
An electronic storage device used to store large amounts of digital information. Computers have a hard disk inside, and so do personal/digital video recorders (PVRs or DVRs). You can store many hours of TV programmes on a PVR's hard disk.

HD
High definition: HD TV has up to four times as many pixels (dots on the screen) as standard-definition TV. The pixels make up the lines on a screen - standard screens have 625 lines, HD screens have 720 or 1080 lines. This gives a clearer, sharper picture with much more detail. HD TV also has better quality sound.

HDMI
High-definition multimedia interface: a digital connection using a single cable for high-quality video and audio.

IDTV (or iDTV)
Integrated digital television: a TV set with a built-in digital TV receiver that can get digital terrestrial TV without a separate set-top box.

Interactive TV
Extra services that let you get extra information about programmes, watch alternative news stories and sports coverage, and join in quizzes and voting. You access interactive features via the red button on the remote control.

LCD
Liquid crystal display: a technology that displays a picture on a flat-panel screen. It is particularly suitable for large-size TV screens.

LNB
Low noise block downconvertor: the device mounted on the arm attached to a satellite dish that receives the signal, converts it and sends it to your set-top box.

Letterbox
The way that a widescreen picture (16:9 ratio) can be displayed on a standard TV screen (4:3 ratio) with black bands at the top and bottom.

Multiplex (abbreviated to MUX)
A single broadcast frequency that contains a number of different digital TV or radio channels. In the UK, six multiplexes carry all the digital terrestrial TV channels and radio networks available on Freeview and Top Up TV. For DAB digital radio, there are two national radio multiplexes (also called ensembles) and a number of local ones.

Nicam
Stands for Near Instantaneously Companded Audio Multiplex: a stereo system developed in the 1980s by the BBC for analogue TV.

PDC
Programme delivery control:

Pixel
Picture element: a single dot on a TV screen (or computer screen or digital photograph). Thousands of pixels make up the picture, and the more pixels the better the picture. High-definition TV has up to four times as many pixels as standard-definition TV.

Plasma
A technology that displays a TV picture on a flat-panel screen by using gases behind the glass. It is particularly suitable for large-size screens.

Platform
In broadcasting, a system for delivering TV and radio services. For example, digital TV is delivered mainly on terrestrial, satellite, cable and broadband platforms.

PPV
Pay-per-view: an individual programme or series that you pay to receive.

PVR
Personal video recorder; also known as a DVR (digital video recorder). It records TV programmes digitally on to a hard disk (like saving information on a computer), instead of on video tape or DVD. It has an electronic programme guide built in, and allows you to pause and 'rewind' a programme while you are watching it.

RDS
Radio Data System: found in many car radios, RDS automatically selects the strongest FM signal available for the station you want to receive, so that you don't need to retune when you are moving around. It can also detect and switch to travel bulletins broadcast by BBC local radio stations.

Receiver
Equipment that receives and decodes signals from a transmitter so that you can see and/or hear TV or radio broadcasts. TV sets (both analogue and digital), digital TV set-top boxes, and radio sets are all examples of receivers.

Relay
A low-power transmitter that receives signals from a main transmitter and retransmits them to a localised area.

RF
Radio frequency: an RF connector is used to feed a TV signal from an aerial to a TV, set-top box, video recorder, etc.

RF loop
Where RF connectors are used to feed a TV signal from an aerial to a set-top box, then out again to a TV and/or a video or DVD recorder.

Scan
When you first plug in a TV set-top box or a DAB digital radio, it does a scan (either automatically or at the press of a button) to find all the available channels.

Scart
A Scart lead has a large, rectangular, 21-pin plug at each end. It is the best way to connect equipment such as TVs, video recorders, DVD players and set-top boxes.

Smart card
Also called a viewing card: a plastic card inserted into a slot in a set-top box or TV that decodes signals and allows you to receive digital services.

STB
Set-top box.

Terrestrial TV
Television that is broadcast from transmitters on the ground and received via an aerial. See also DTT.

Uplink
A signal sent up to a satellite from the ground.

Viewing card
A plastic card inserted into a slot in a set-top box or TV that decodes signals and allows you to receive digital services.

VOD
Video on demand.

Webcasting
Broadcasting via the internet.

Widescreen
TV pictures with an aspect ratio of 16:9 that gives shape like that of a cinema screen. The programmes on most of the major TV channels are now in widescreen format.

Wi-fi
Short for 'wireless fidelity', wi-fi is a technology that lets you connect to the internet and share computer files without cables.