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james-20014,113 posts since 13 Sep 2015
Central (East) East Midlands Today
I think its only been relatively recently it became possible to record teletext from Standard Play VHS recordings. Previously it was only the preserve of recordings made on SVHS and possibly Betamax (maybe even Video 2000?) where it was possible with enough time and effort.


I think I was able to record a pretty decent teletext picture using a four head VCR.


Part of the key to success was where the head switching point was. Obviously it had to be in the VBI, but in some cases it wasn’t on the teletext data lines


Not always in the VBI, on some recordings you still get a lot of head switching noise at the bottom of the frame.
Markymark6,153 posts since 13 Dec 2004
Meridian (North) South Today

I think I was able to record a pretty decent teletext picture using a four head VCR.


Part of the key to success was where the head switching point was. Obviously it had to be in the VBI, but in some cases it wasn’t on the teletext data lines


Not always in the VBI, on some recordings you still get a lot of head switching noise at the bottom of the frame.


Yes, during the last few lines of active picture, and the equalising pulses. It's amazing what crap of mangled up signals and noise you can throw at most tellies, and they still produce a watchable picture
Riaz558 posts since 6 Jan 2016
That was probably far less of a problem in the 90s, than it is now


?????????????

Remember the Computer Misuse Act 1990.

The fact is, if confidential information is transmitted over the airwaves with no or weak encryption that any Tom, Dick, or Harry can receive whilst also being impossible for anybody to detect then surely somebody will start to eavesdrop then misuse or disseminate this information.

Even businesses could use information intended for their competitors (like price updates on products) for an unfair commercial advantage.
Markymark6,153 posts since 13 Dec 2004
Meridian (North) South Today
That was probably far less of a problem in the 90s, than it is now


?????????????

Remember the Computer Misuse Act 1990.

The fact is, if confidential information is transmitted over the airwaves with no or weak encryption that any Tom, Dick, or Harry can receive whilst also being impossible for anybody to detect then surely somebody will start to eavesdrop then misuse or disseminate this information.


The point I was making was back in the 80s and 90s you had an order of magnitude fewer people trying
to hack into systems and data, therefore 'less of a problem'
1
bilky asko gave kudos
Riaz558 posts since 6 Jan 2016
The point I was making was back in the 80s and 90s you had an order of magnitude fewer people trying to hack into systems and data, therefore 'less of a problem'


The exact numbers remain unknown and figures only exist for instances of hacking or eavesdropping that were reported or otherwise made public knowledge. Many cases were never reported, out of fear of embarassment or because it could further compromise security, or were even detected in the first place.

Incorporating confidential information on the VBI of a TV broadcast will undeniably attract eavesdroppers like kids to sweets because it can so easily be received.
Technologist9 posts since 10 Oct 2018
London London
Thanks @riaz for your long account of the USA story ....
my point was in cross ownership of media outlets print and electronic in a market...

But in the UK there were a number of reasons to have Teletext....
And still some but fewer in Europe
But the USA did not grasp the multiple possible uses
And they had the diversion of choosing standards .....
And the Japanese not yet putting teletext in NTSC TV sets ...

On security of Databroadcasting ....
The users had a multilevel view ...
It needed some skill to make and operate something to decode the VBI ...
Then the data was encrypted in any case over the modems to the origination equipment.
And some did more/different techniques for the transmitted signal ..
And there was also often additional false data.
But how much you put on depended on application ...
from very little for say the milk tanker or the stop betting command.
To a lot more for the stock exchange real time data ...

On the Ceefax front there was one company who made a stock exchange systems that used the
Slightly delayed prices in breach of the T&C of Ceefax
And obviously if the BBC did nothing the feed would have been removed ..
So using the pages themselves the BBC crashed the "illegal " stock exchange system
Very effectively whilst still,giving the tv viewer perfect pages ...
Ceefax and the techies did not tell anyone how it was done ..
But the company providing the information was very very impressed ...
They had a few sets of "illegal" kit ..... all of which stopped working
Despite the BBC not having a system to play with ...
( but some very annoyed customers of the "illegal" system phoning up ..
to complian )

But Peter Weitzel's mention of blowing up,a decoder is the ultimate security...

Incidentally on satelite broadcasting where the picture and audio was scrambled
it was rare that the VBI was scrambled
so you could watch subtitles over scrambled picture ..
Or receive the databroadcasting feed easily !
Riaz558 posts since 6 Jan 2016
There is the ultra cynical theory as to why teletext never caught on (with broadcasters rather than the public) in the US. It is because around 20% of the adult population (higher in certain localities) in the 1980s were functionally illiterate or cannot read anything other than short words or phrases - such as road signs. The American TV companies held the view that TV was invented as a means of obtaining information without having to be able to read, so implementing teletext services would defeat the objective of TV as they could only be used by people with the ability to read. In western European countries where adult literacy was around 99% in the 1980s then there was a case for offering teletext services but in the US there was something unAmerican about teletext.

Teletext was deployed in Europe as an information system but closed captioning was deployed in the US as a disability aid that was not meant to be used by people unless they were hard of hearing. Although they both used the same underlying principle they were developed in parallel for different purposes and different audiences.

The US had thousands of dial-up BBS systems during the 1980s offering a diverse range of information and services. They were not mainstream technology for the masses but overall they were more successful than BBS services were in Britain. Ceefax and Oracle were mainstream and successful but Prestel was a complete failure. Some Americans claimed that BBS systems were superior to teletext services because they (collectively) could offer a much more diverse range of information and they were interactive whereas teletext was monodirectional.

There have been arguments that the BBS in the US vs teletext in western Europe contributed to a higher percentage of internet users in the 1990s and early 2000s in the US than in western Europe but there were several other factors at play.
WW Update4,441 posts since 6 Feb 2007
In Europe, teletext was spearheaded by well-funded public service broadcasters, who could afford to invest in a non-profitable (or at best marginally profitable) technology. In the U.S., with its commercial set-up, broadcasters quickly realized that there wasn't enough money in teletext, so there was no incentive for anyone to develop it.

Besides, the United States wasn't the odd man out when it comes to teletext -- it was Europe. The medium remained marginal in Asia and Australia (with only a single broadcaster adopting in in the latter case), and all but non-existent in Africa and Latin America.

Therefore, rather than wondering why teletext never caught on in the U.S., we should probably be asking ourselves why it caught on in Europe.
Last edited by WW Update on 6 February 2019 5:05pm - 4 times in total
Riaz558 posts since 6 Jan 2016
Besides, the United States wasn't the odd man out when it comes to teletext -- it was Europe. The medium remained marginal in Asia and Australia (with only a single broadcaster adopting in in the latter case), and all but non-existent in Africa and Latin America.


Take into account that many countries in Asia and the Middle East use languages with different alphabets. Pakistan used to (and might still) operate an English language teletext service.

I'm not sure if teletext was ever adapted to work with the SECAM used in the Middle East, Russia and former communist countries, or French speaking Africa which were different from the SECAM used in France. If it wasn't then that will explain why these countries did not have teletext although some of these countries later switched to PAL.

Was the lack of teletext in Latin American countries that used NTSC a result of them having the same models of TV that were sold in the US that didn't include teletext decoders? Argentina, Uruguay, and Chile used PAL but did they ever have any teletext services? Brazil had a unique PAL-M standard which was the same as NTSC but with PAL colour encoding.

Quote:
Therefore, rather than wondering why teletext never caught on in the U.S., we should probably be asking ourselves why it caught on in Europe.


It might have been a combination of factors.
Neil Jones4,795 posts since 23 Dec 2001
Central (West) Midlands Today
Wiki suggests Secam was teletext capable (or had been adapted or whatever, since it originally had 819 lines as opposed to the later European standard of 625 lines) and anywhere that took the NTSC format was virtually doomed to failure. Argentina used 625 PAL as well but it appears to have been "butchered" for want of a better word for Closed Captioning support.
WW Update4,441 posts since 6 Feb 2007
Most Latin American countries had weak or non-existent public service television, so there was no real incentive to introduce teletext technology, regardless of whether they used PAL, PAL-M, or NTSC. There were (and are) few BBC- or even ITV-style broadcasters in Latin America. For the most part, they are privately owned, fully commercial, and with few public service obligations.
noggin14,037 posts since 26 Jun 2001
Wiki suggests Secam was teletext capable (or had been adapted or whatever, since it originally had 819 lines as opposed to the later European standard of 625 lines)

France and a few Francophone bordering countries ran 819 monochrome services, but these weren't SECAM services, they were B&W. You can't have B&W SECAM - as SECAM is specifically used to define the colour system only (The letters actually stand for "Séquentiel couleur à mémoire" or "Sequential colour with memory")


Whilst there may have been some 819 SECAM tests (just as the UK tested PAL, SECAM and NTSC 405) - it was never a formal system, and the days of 819 were (like 405 in the UK) numbered by the mid-60s. (Long before teletext)

France only had one 819 channel (what is now TF1) - the second channel (now France 2, previously Antenne 2 etc. ) which launched later was, like BBC Two in the UK, 625 B&W from launch, and then the 625 channel was upgraded to SECAM colour, whilst the 819 channel simulcast in 625 (and SECAM colour)

France's 625 SECAM services had Antiope (an incompatible French teletext standard) for quite a few years, until they switched to WST Teletext. (Incidentally France also modified their SECAM system to use a different chroma reference system - from 'bottles' in vertical blanking to horizontal idents, which freed up space in the vertical blanking period)

Quote:

and anywhere that took the NTSC format was virtually doomed to failure. Argentina used 625 PAL as well but it appears to have been "butchered" for want of a better word for Closed Captioning support.


Argentina used 625 PAL but the PAL-N variant designed to fit into 6MHz channels, and as such used a 3.58ish rather than 4.43MHz subcarrier for colour (4.43MHz wouldn't have fitted in a 6MHz channel), and had reduced luminance bandwidth. Conventional 625 VBI teletext may not have worked that well there with the reduced bandwidth...

Brazil used 525 PAL M - which used a PAL colour encoding system at 525 lines with a 3.58ishMHz subcarrier - but would have had to have used a similar teletext system to NTSC M for bandwidth/line standard reasons I suspect.
Last edited by noggin on 7 February 2019 1:15am - 2 times in total