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                             Issue #6 - Page 3 of 16 
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The History And Application Of TELETEXT

Written by GPC
On 14:54 21/04/02
heelflip_the_biscuit_tin@hotmail.com

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 You may ask yourself, why is GPC doing an article on TELETEXT and more
importantly, who is GPC? To answer the latter I am GPC (duh!) or Geldoff's
Poor Cousin. Anyway, I'm writing an article on TELETEXT because it was really 
the first time that technology and the media were fully integrated but also 
cos I happen to think that TELETEXT is quite dope :D.


Frequently asked TELETEXT (hense forth abbreviated to TT) questions:

1. What is TT?
Well if u live outside Europe, chances are you'll never have heard of TT.
This is cos for sum reason TT never really took off in America, and every1
else in the world does what America does (apart from Europe :P). But
politics aside, TT is a 'data carousel' (more about that later) text
information service that holds information in a linear ASCII format. It has 
info on things such as TV listings and sports news. Teletext also has 
subtitles (known as 'closed captions' in the US) and can display half on,
half off (its difficult to describe).

2. How does it work?
The actual teletext pages are broadcast in a hidden part of the television
signal (the Vertical Blanking Interval), and decoded by the television.
Teletext pages are accessed by a 3-figure number; on most channels, the
front page is on page 100.

3. Why isn't it instantaneous?
Many people ask this, as, after all, the information is just text and in
some cases it can take minutes to load. This is because when u select a
page, say 456, theres no way of telling the TT provider what page u have
asked for because analogue TV is only one way. So instead, the pages go
around on a 'data carousel' and this carousel will only stop at the page u
request. This way there is no user to provider link needed.

4. Isn't TT crap tho?
Well yes and no. Its not graphical apart from where ASCII is used to convey
images. It is, however, extremely helpful for txt services and it requires
no special equipment, technical knowledge or encur call costs. For these
reasons over 22 million people use teletext in one week.

5. Why cant the TV just cache the pages?
This is cos nearly all TVs dont have a cache, let alone the programming to
cache pages automatically. Plus there is a chance of blue screen moments of
death when the info in the cache clashes with ne updated info on the page.
But, if you have a TV card on ur box ur comp can cache it.


Digital TELETEXT

 Digital television has 'digital teletext'. Despite the name, the only 
thing common to 'analogue' teletext is the fact that the viewer looks at 
information on the TV screen. The methods used to broadcast and decode it, 
as well as the way it looks, are much removed.  Some channels on 
SkyDigital, the UK's digital satellite operator, carry analogue teletext 
despite the promise of digital teletext. Sky's own-brand channels carry an 
expanded version of SkyText, although it directs viewers to the Sky 
Electronic Programme Guide instead of carrying TV listings.  Channels on 
the UK's digital terrestrial channels don't carry analogue teletext. This 
was due to a decision by The Digital Television Group (DTG), who decided 
that such things were unnecessary. In the long term, this is probably 
true.  Teletext Ltd. will be provides a service on channel 9 of digital 
terrestrial television with the BBC Text on channel 10.  To complicate 
things for the providers of digital teletext, the systems opted for by Sky 
and DTG are different. Whilst DTG decided to use MHEG-5, which is an ISO 
standard, Sky decided on OpenTV. OpenTV is a proprietary 'solution for 
digital interactive receivers'. Teletext has a demo of Digital Teletext on 
their web site; the BBC also has some information on their digital site and 
in a paper (in PDF format).

Recoding TELETEXT

 Direct recording of TT is quite difficult but it is possible to decode the
old text pages from old S-VHS video tapes that also recorded the vertical
blanking interval.


Thats it every1, I hope this has opened ur eyes. Next time ur waiting for
the page u want to come round on the loop try to appreciate how amazing it
is :D

 - Geldoff's Poor Cousin
heelflip_the_biscuit_tin@hotmail.com

   (Stop laughing Timeless :P)
