|An aerial collects a terrestrial television signal to feed a TV set or Freeview set-top box. Click for more.
|Another name for a booster.
|Until the invention of digital computers, all technology was analogue. In an analogue system the sound and light that is detected by the camera and microphones in the TV studio is converted to waveforms that directly represent sound and light levels, and then converted directly to a picture and sound on the TV set.
|Antenna is the American name for an aerial.
|Astra is the name of the company that provides the satellite that Sky Digital uses. They have a number of satellites which are said to be at 23.2 East, called the Astra 2 satellites. The Astra 1 satellites are at 19.2 Eat and were used for the old Sky analogue satellite system.
|Watch live BBC TV channels, catch up on TV programmes you missed and view exclusive content on BBC iPlayer. Click for more.
|A booster is a device that attempts to increase the signal strength of the terrestrial television signals to provide better pictures and sound. Whilst useful with analogue television, they are most useful for digital television when an adequate signal need to be sent to several sets or set-top boxes. Often a booster can degrade digital television. When a booster is attached directly to the TV aerial, this is called a masthead amplifier. Click for more.
|A cable is one or more metal wires which are covered with a plastic coating usually with a plug (or socket) at each end. These can be used to carry power or signals between devices. Different types of cable are used for different tasks, such as co-axial cable for signals from aerials and dishes, SCART cables for set-top box to TV connections or mains cables to supply power.
|The subscription digital services, Sky Digital by satellite and NTL:Telewest via cable, and the Sky Freesat service require a special computer chip that identifies the subscriber to their digital TV box. This chip is mounted in a credit-card sized viewing card.
|Channel has two related meanings. It can refer to a single, branded scheduled station of programs, such as BBC one. It can also refer to a transmission frequency that is used to broadcast a single TV station on analogue television OR a multiplex of several TV stations on digital television.
|The name for a Sky digital satellite decoder box is a Digibox.
|Computer systems use basic units that are built round digital values, which can be either 0 or 1. The simplicity of binary values allows fast microprocessors to be built efficiently. By applying digital technology to television it has been possible to provide more choice or higher quality to the viewer which was simply impossible using analogue systems.
|Due to the shape of a satellite reception device, it is usually referred to as a dish. However, not all are dish shaped. Click for more.
|electronic program guide
|Most digital television systems allow you to use the remote control to view the programs that will be on all the channels over the next week or fortnight. This is called an electronic program guide or EPG.
|Repair work to transmitters is usually called engineering.
|Freesat is a satellite TV service with no subscriptions, offering HD digital television through a digital box, with over 200 TV, radio, interactive channels, on demand and more. Switch today and save
|Freeview is the name of the terrestrial digital television service in the UK. It provides around 30 television channels and 30 radio stations and a number of text and interactive services that require no subscription. It can be received using a normal roof-mounted TV aerial, but currently broadcasts to only 73% of the population from 80 transmitters.
|The frequency is usually refers to the number which is used for transmission of a TV or radio signal, usually measured in megahertz or gigahertz. Because of the nature of the system, there are a limited number of these frequencies that can be used.
|The gain is the measure of signal increase provided by a booster or amplifier.
|Because there are a limited number of transmission frequencies, they have to be used on more than one transmitter. If you can receive a undesired signal which causes the picture to be degraded (on analogue TV) or prevents proper digital reception, this is called interference.
|With analogue terrestrial television is has, in places with strong signals, been possible to receive a acceptable signal by mounting an aerial in the loft space. However, this is not recommended for Freeview reception. In some areas, such as New Towns, National Parks and Conservation Areas rooftop aerial have been banned, and loft installations were the only option possible.
|Power that is supplied by the wall sockets in your home is often called the mains, to distinguish it from power supplied by batteries.
|Terrestrial television transmitters are often found at the top of tall metal structures called masts.
|A signal booster located on the rooftop aerial, rather than by the TV set, is called a masthead amplifier.
|The CODFM system that is used to transmit Freeview can be configured in a number of different ways. Two are used in the UK at the moment, and these are called 64QAM mode and 16QAM mode. The former is slightly harder to receive than the latter, but provides more bandwidth which is used to increase the number of channels.
|When digital television was implemented, it became possible â€“ by using digital technologies â€“ to transmit several TV channels using the same amount of frequency that one analogue channel used. The technique is called multiplexing. Freeview provides up to six multiplexes (1, 2, A, B, C and D) each with between four and eight TV channels multiplexed onto each transmission frequency.
|On television and radio the word network refers to the group of channels provided by a single broadcasting company or corporation. The ITV network refers to the historic regional companies coming together, the BBC radio network is all the BBC's national and local radio stations. However, a computer network is term used for any system that connects computers together, usually a Local Area Network (LAN) or a Wide Area Network (WAN).
|Ofcom is the organization that regulates companies that provide television, radio and internet services in the UK.
|In any television or radio system the source of the programmes will be in a single studio and the programme will be watched or listened to in many homes. Any device that transfers the signal in the studio to home direction is an output. So with a Sky system, the dish has an output on the LNB, the Digibox has a SCART output, the TV may have a speaker output too. Normally each output connects directly to a single input on another device.
|A personal planner is a feature of some electronic program guides, which allows you to set reminders to watch particular programmes. Click for more.
|personal video recorder
|A personal video recorder, or PVR is a device that can record digital television onto a built-in computer hard drive. Examples of these are Sky+ and Freeview Playback. A PVR can usually provide an electronic program guide, record two TV channels whilst you watch a recording and provide instant access and allow you to pause live television. Click for more.
|In television, the word picture refers to one of the two components of a TV channel, the other being sound. The moving video image you see when watching TV is actually 25 static pictures each second. Poor digital reception sometimes results in the picture not changing, and the picture is said to freeze.
|The word power has two uses. It can either refer to the mains electricity that has to be supplied to a TV set or set-top box. It can also be used to refer to the signal strength of a transmitter, or the strength of that signal at the receiving end.
|meaning signal quality
|The term used for a TV set, Digibox, Freeview box or radio that plug into an aerial or dish and outputs pictures or sound is a receiver.
|The places that TV or radio can be received from a transmitter is called the reception area, and reception itself refers to the process of receiving a signal from a transmitter.
|To provide more localized TV and radio services, historically ITV1 and BBC one have been divided into regions. These regions represent those areas covered by a main transmitter and its relay transmitters. The regions have more to do with the location of the transmitters and the terrain than the political boundaries or county borders. Click for more.
|There are over 1000 TV transmitters in the UK. Around 80 of these are main transmitters which provide TV for 90% of the population, and the rest are used to fill-in for the remaining 8.5%. Whereas the main transmitters have their signals provided to them by underground optical fibre networks, the relay transmitters receive their signals from the main transmitters and simply retransmit them.
|For optimal Freeview reception is necessary to mount your TV aerial outside positioned as high as possible with a line-of-sight to the transmitter, this is called 'on the roof' but often means it is actually mounted on a pole attached to a chimney stack.
|A satellite is a transmitter that has been launched by a rocket to orbit the earth. Most communications satellites orbit at the same speed that the Earth turns, and so appear be in the sky in stationary position.
|When you first plug in a receiver, it must first determine which frequencies it can receive channels on. It does this by testing all the possible frequencies it can use, and this is called a scan. Click for more.
|A SCART cable has a large rectangular plug at each end is used to connect television, DVDs, set-top boxes to each other. Unless you have a HDTV system, a SCART cable is the best option to connect these devices together. Click for more.
|Digital television provides TV channels, radio stations, interactive text services, electronic program guides and interactive TV channels. These are collectively called services.
|The signal is the radio wave that carries an analogue TV station over the airwaves, or a multiplex of stations for digital television. The power of a signal decreases exponentially from the transmitter. A weak signal will result in degraded analogue television pictures. The signals from satellites are very weak indeed and require a dish to obtain a stronger signal.
|To allow many different manufacturers to make equipment that operates with that provided by others, they are said to use a standard. These standards have abbreviations such as DVB, DVB-S, DVB-T, DTT, DVB-CS, HDTV, HDMI, COFDM, DVB-H, DAB, MPEG, DVD and so on.
|A television or radio channel which supplies scheduled programs is sometimes called a station.
|Any television service that you pay for (and is not free TV) requires regular payments, and you usually have to have a subscription for at least 12 months.
|Currently in the UK, terrestrial television is transmitted as using both analogue and digital techniques. This has been very useful for those who either did not wish to upgrade to Freeview, and for the 73% of the population that have been able to pick up Freeview signals. However, the system is very wasteful in the long term, and does not allow the remaining 25% to watch Freeview. Between 2007 and 2013, region by region, the analogue system will be closed down and replaced with Freeview signals to cover the entire UK. This will require anyone using analogue TV to upgrade all their TVs, VCRs and â€“ for many people â€“ their TV aerials. Click for more.
|Broadcasts that use transmitters on the ground, rather than satellites or underground cables are called terrestrial.
|A transmitter is usually a large, tall tower built as high up (on a hill or skyscraper) that emits the signals that provide analogue television, radio or Freeview. For reception the receiving aerial has to be directed to the transmitter and should have a line of sight to it.
|When analogue satellite television was started each TV station had its own frequency, and these ware called transponders. With digital satellite several TV channels are carried (using multiplexing) on each transmission frequency, but the name transponder is still used. There are over a hundred transponders on the Astra 2 satellites.
|Television and radio is regulated and you require (in the UK) a licence to transmit or receive. Broadcasters need various licence from Ofcom, and any home or business with a television set must have a TV licence. The official TV Licensing website contains a wealth of information about the TV licence, who needs to pay it and how to pay. Click for more.
|As digital television boxes are small computers, their software can be improved and enhanced and delivered to homes via Freeview, cable or satellite systems. When new software is installed it is called an upgrade.
|The word video can refer to video cassette recorder, the tapes you put in a video cassette recorder, a short film accompanying a music track or the moving pictures you see on a TV screen.
|To prevent, mainly with analogue television, visible interference from transmitters other than the desired one many TV aerials are said to belong to a group. Freeview and analogue channel five has, at many transmitters, used transmission frequencies that are in a different group to the original one. An aerial that can receive on all frequencies is called a wideband aerial. Click for more.