Communication Methods : Digital Television

Digital television was introduced in the UK in 1999. Eventually the digital television system will replace the current analogue system. Digital television has a number of advantages over analogue television. In particular :

  1. Many more channels can be broadcast at the same time using digital television than using analogue television.
  2. Digital pictures suffer less from interferance that analogue pictures.
  3. Digital pictures can be transmitted in a range of formats such as widescreen.

To receive digital television you must either purchase a special decoder or a new television with a decoder built into it. Digital television can be received by satellite, radio waves or fibre-optic cable. Most digital television decoders also include a modem which can be used to connect the decoder to the telephone network so that data can be sent from the viewer back to the television channel. This enables the provision of interactive television where the user can influence what is transmitted.

The companies that run digital television channels have used the capabilities of digital television to provide a range of new services such as :

Television
Internet 		Television Internet is a limited Internet service which can be viewed on a television. A computer is not required to access television Internet. Some World Wide Web pages can be viewed and email can be sent and receieved. The data is transmitted over a telephone line using the modem in the decoder.
Pay-per-View A pay-per-view system can be used to make viewers pay for particular programmes that they choose to watch. Pay-per-view is often used for popular events such as boxing matches or film premieres. To watch a pay-per-view program you must use your decoder to pay for the programme before it is transmitted. The decoder sends payment details to the television channel using its modem.
Pseudo
Video On
Demand 		A video-on-demand service lets the viewer watch a television programme when he wants to. The user chooses the programme from a menu and it is transmitted to his television when he wants to see it. Such systems are very expensive to set up and use but a simpler system called pseudo video-on-demand can be used with digital television. The viewer can choose the programme he wants to view from a short list of programmes. Each programme is transmitted every 15 minutes on a different channel. Once a viewer chooses a program he has to wait no more than 15 minutes before it starts. This system works because a lot of channels can be broadcast at the same time on a digital system.

Digital televisions integrate a number of different functions from broadcasting and telecommunications into one product. It is likely that further integration of different communications technologies will take place in the future.

GCSE ICT Companion 04 - (C) P Meakin 2004