Teletext is hardly
comparable to the
internet for one simple reason: it's a one-way
medium (although with some very
complex page programming and a bit of
social engineering to persuade the
viewer to pick up their
telephone it can be
made
interactive in a very
crude way).
That having been said, if a technology which was invented in the early 1980s is still
in widespread and general usage today it must be doing something right.
Teletext works by inserting data into the unused scan lines which appear above and
below the broadcast picture on any TV set. In other words, your TV can display 625
lines of image, but the TV companies actually broadcast 640. Some of these "unused"
lines carry control signals to help the TV keep its picture tuned-in and
synchronised, but there are some spare lines.
Teletext is based around a 40x25 text-only display (although it has some
block graphics similar to those from ANSI DOS), and each of these 1000-byte
pages (actually a full kilobyte due to transmission of parity check bytes and
other control information)
is numbered between 100 and 799. Using special remote control handsets
viewers can select these pages, either by keying in the correct number or by
following a series of coloured menus.
Common applications include: news, TV guide and subtitles on programmes
for the hard-of-hearing. In the UK at least all of the terrestrial television channels
carry very comprehensive pages covering all of the above and much more,
as well as most of the larger satellite and cable channels. Many
of the pages carry local content which is inserted by the particular regional TV station
making the actual transmission. This means you could be watching a programme on
BBC1, for example, while still reading the news local to your region on teletext.
Despite being potentially threatened by the arrival and popular uptake of
Digital Television and the internet, both of which allow
full interactivity at greater graphics resolutions,
teletext is such a simple and well-known system that it's unlikely to vanish any
time soon. I for one am glad of that: despite having access to all sorts of
information resources I still find it easier to turn on my TV, pick up the remote and
press <Text><Yellow> to get up-to-date news headlines than anything
else.