> Videotext never really caught on in the US except on cable TV as a
> non-interactive display. I believe there are still a few videotext services
> piggybacking on satellite channels. They transmit on one of the unused scan
> lines at the top of the picture, similar to closed captioning for the deaf.
>
> To my knowledge the only truly successful videotext implementation
> was the french minitel telephone directory.
data piggy-backed on TV signals, using several lines in the blanking interval,
is called viewdata.
data presented in the same screen format as viewdata, but interactively, over a
phone line, is called videotext.
Collectively, videotex = videotext + viewdata.
The original standards were for 25 lines of 40 columns, in 8 colours.
Characters can have attributes like "flashing" or "hidden" (for quizzes), and
there are rudimentary graphics using a 2x6 mosaic pattern in each character
cell.
There are several not-quite-compatible viewdata standards, some of which offer
much higher resolution and colour range (the German Bilschirmtext system BTX
does this). AFAIK, all the videotext systesm, at least in Europe, are the
same, and the BBC and UK independent TV companies all use it for news,
programme listings, etc, as do a lot of the european satellite TV channels.
UK's PRESTEL, Germany's BTX, France's Minitel, all use slightly different
forms. Lots of UK travel agents use a private PRESTEL-compatible system, and at
least a couple of banks and building societies here use the same standard for
home banking. A few UK bulletin boards used to use the same format, and I
think one or two still do, for nostalgic reasons. You can get two or three
host systems to run on machines like BBC Micros. There's a web page somewhere
devoted to this old stuff, but I can't remember the URL (if anyone really wants
it, I'll look). There are BTX and Minitel emulators for X-windows, and I have
a PRESTEL terminal emulator package for X-windows (works well but still needs a
bit of tidying up) which AFAIK is the only free PRESTEL-compatible one for unix
systems.
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
Received on Fri Mar 20 1998 - 20:37:51 GMT