What’s interactive TV?

Digital TV receivers give access to different levels of interactive TV, depending on whether they are designed for satellite (Sky Digital), cable, or over-the-air terrestrial (Freeview) reception.

Each platform uses a different type of system to do this. In terms of sophistication, that used by the UK's two cable companies, Telewest and NTL (soon to merge), ranks highest, followed by BSkyB's and Freeview's. Freeview's is the most primitive because it is the only one of the three platforms that does not have a so-called 'return-path' - i.e. the viewer can not send messages back to the interactive service provider.

Interactive TV enhances the TV viewing experience in two ways. The first of these involves calling up extra information in the form of text and/or still images which is either independent of what you happen to be viewing at the time (a sort of souped-up version of Teletext) or which is tightly related to it (for instance, background information amplifying the documentary you happen to be watching).

The second involves the ability to access one of several different programming ‘streams’ transmitted in parallel. The best example of this is the BBC’s interactive coverage of Wimbledon, which allows viewers to choose which court they wanted to watch. BBC news also offers a sophisticated interactive service which allows you to choose, within certain limits, which news items you want to watch.

These types of interactivity do not actually involve the viewer sending information back to the service-provider to elicit a response: they simply extract an additional layer or layers of information that are being broadcast alongside the digital TV programme. These types of interactivity are the only ones that Freeview is capable of offering, because - as mentioned above - it has no return-path. 

Cable and satellite receivers, however, have a modem integrated into them, which means that they can offer ‘genuine’, two-way interactivity in addition to the modes described above. This makes it possible to vote, send emails, play games, even buy goods via the TV screen. On cable, there is also the possibility of surfing the Web.

While Freeview doesn't currently have access to a return-path, future versions of the interactive software it uses will be capable of dealing with two-way interactivity, and some Freeview receivers (set-top boxes as well as an increasing number of IDTVs), already have either integrated modems or the right connections to hook one up. And next year (2006), BT will be launching a Freeview set-top box that includes a broadband connection.

If you are interested in this type of facility, then you should consider whether such a feature needs to be on your shopping-list to ensure your receiver is future-proof.