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Teletext

Posted by Big Boo on March 3rd, 2009

teletext

I still remember my first exposure to teletext.  It would have been the early eighties when I went to visit one of my uncles.  He had just got a new TV (which he rented from Radio Rentals) and it made our TV at home look old fashioned.  Whereas our TV had big push buttons to change channels and was encased in wood, my uncles new telly was made of plastic and came with a remote control.

This was the first time I had ever seen a remote control, and I was initially fascinated how this little box, with no wire connecting it to the TV, could switch the channels.  Impressed, my jaw hit the ground when my uncle pressed one of the other buttons and BBC1 was replaced by a page of text with the magical sounding word CEEFAX written in big yellow letters across the top.

Ten minutes later I had learned how this amazing new feature worked, and I spent the rest of that evening glued to the TV exploring all the various pages available.  My excitement grew when I realised that flicking the TV over to ITV gave me a whole new set of pages called ORACLE to explore.  When it became time to go home, I didn’t want to leave, and spent most of the journey home asking Mum and Dad if we could get a TV with teletext.

Teletext services were originally invented back in the early 1970’s though, when the TV companies were looking to find a way to provide written captions for the hard of hearing.  The BBC were first to the market with the CEEFAX service (see facts – geddit) but ITV followed soon after with their ORACLE offering (which was an acronym for the rather long winded and technical sounding name Optional Reception of Announcements by Coded Line Electronics).  It wasn’t until the 1980’s though that enough people had TV sets capable of displaying the teletext pages that things really took off.

So how does teletext work then?  Well, in those days the teletext information was sent as part of the TV signal during the space between frames.  Between each frame of a television picture there is a period called the vertical blanking period.  This time is needed for the TV set to return the electron beam gun inside it back to the top left of the screen.  During this time a page of information could be encoded and sent, and the TV set could decode and display it.

Since only a small amount of data could be sent in the vertical blanking period this was why you had to sit and wait for your chosen page to appear, as all pages were sent in a repeating loop one after another, which could be seen by the page number display at the top of the screen that kept incrementing and then starting again.

When Channel 4 started broadcasting they launched their own service called 4-Tel, and this quickly became a favourite with kids.  CEEFAX always had a few kids pages but 4-Tel had loads more, with puzzles, games, news and best of all a cartoon strip.  It may have been crudely drawn given the graphical capabilities of teletext, but the adventures of 4-T the dog became compulsive viewing.  4-Tel also had a rather good videogames magazine called Digitiser, which was written in quite an entertaining style, and wasn’t afraid to tell you when a new game was rubbish!