Teletext Revival, Part 1: What Is It? moonlit May 21, 2013 Tech Life 1 Comment Welcome to Teletext, an ITV Teletext splash screen/index page. If you’re British, or even European in general, and you’re an adult, you probably remember the 8bit broadcast glory that was teletext. If you aren’t or you don’t, here’s a little primer to give you a taste of what millions of people used to use for their up to the minute information fix before the internet was a thing. Primarily in Europe, amongst a few other places, there existed a service called teletext which was essentially a read-only BBS service transmitted over regular free analogue TV. It lived as a series of on/off binary pulses in the VBI, or vertical blanking interval. This was an unused area of the picture which served as a blank area during which the electron beam responsible for drawing the picture on the front of the tube in a CRT TV would return from the bottom right of the screen back to the top left in order to begin drawing the next frame. Example of binary teletext data located in the VBI of a TV signal. In practice how people experienced this service was via a “Text” button present on practically all modern TVs from perhaps the mid-1980s onwards, which displayed text data as an overlay over the TV picture. It provided TV and radio listings, news, weather, sports scores, primitive cartoon strips, music/game reviews, recipes and much more besides. It even offered downloadable software for a brief period, if you had a compatible home computer of the era which was capable of receiving the signal, similar to a modern day TV tuner card, but usually incapable of displaying the actual TV picture. BBC Ceefax’s Telesoftware magazine. Channel 4’s Oracle/4-Tel Telesoftware magazine. Users would navigate the service by punching in a 3 digit number on their remote control, or later on in its lifetime by pressing red, green, yellow and blue buttons which acted much like HTML hyperlinks, as shortcuts located along the bottom of the screen. Incidentally, the 3 numbers which made up a page number were not decimal, but were actually a combination of one decimal number between 1 and 8 which would denote the “magazine” (simply a collection of pages) number and a hexadecimal number which designated the page itself. With that said, almost all pages intended to be publicly accessible were numbered with what appeared to be decimal numbers, because consumer TV remote controls had no alphabetical buttons. One exception that springs to mind was a quiz game on UK Channel 4’s Teletext service, which used hex numbers as the landing pages for both correct and incorrect answer selections, presumably to either prevent the need for many otherwise useful page numbers being used up or to help prevent cheating, although there were methods of cheating regardless. Since I mention this method of cheating, it seems relevant to mention that teletext was a reasonably slow service, because all the pages had to be transmitted one after the other (though not necessarily in order), causing the TV to have to wait for the desired page to be re-transmitted again. This was remedied somewhat by having the TV cache pages in memory so that by the time you choose another page, it had already been received whilst you were reading another, or simply watching TV. The cheat, however, would have benefited from a TV which wasn’t very good at, or didn’t have, caching, because to find out the answer to a quiz question without hitting a “wrong answer” screen, you would press the red, green, yellow and blue answer buttons in quick succession, three of them would be identical and would lead to the failure screen and one would be unique and would lead to the next question. A Bamboozle quiz question page. Note the page number, 12B. Anyway, I’m rambling, what’s the point of all this? Well, analogue TV is dead, or very quickly dying where it’s not yet entirely gone, and in the UK at least it sadly took teletext with it. It’s possible to include this original “analogue” teletext in modern digital signals but for whatever reason it’s been decided that for UK television, it’s time to bury it and replace it with MHEG5 “digital teletext”, transmitted over DVB-T. But I don’t think that’s cool. I think that for a free digital data service that lasted 40 years, it deserves more than a memory. It was important to a lot of people, whether it be the old man listening to the radio with the instant football scores popping up on the TV screen or the hormonal teenager scrabbling to find anything remotely countercultural in Channel 4’s Digitiser teletext magazine, it was the go-to location for so much information, when people didn’t have computers and even if they did, it’s far quicker to click on the TV and punch in a 3 digit number than it is to wait 5 minutes for a creaky old machine to boot up, then dial up the ISP, so on, so forth. The final goodbye from BBC’s Ceefax teletext service, taken from Pages From Ceefax, a filler TV programme usually played in the early morning, consisting of pages from Ceefax rendered as a TV show with easy listening music. But there’s a problem. With, for example, a dialup BBS, or an old home computer architecture, we had easy access to these things, we can know how they work and we can replicate them, we still have BBS servers, we still have IRC, we have emulators of computers long, long forgotten. However, teletext was very much a server-side kind of deal. To produce a teletext signal, with few exceptions over the years, you generally needed obscure and expensive broadcasting equipment. Now granted, the BBC Micro came with its very own teletext mode, which some games and applications ran in, it could even receive the real deal if you had the appropriate beige wedge hooked up to give it access to the airwaves. What might have been useful is that the BBC Micro, having had such a mode generated by the very same chips used in TVs, can be used to design teletext pages exactly how they would appear on a TV set. But that’s a BBC Micro, itself 30 years old, so not altogether useful given that they’re getting rarer and more expensive all the time. I’ve attempted to capture the essence of teletext a number of times myself, I tried to write a custom client which would simulate teletext on a PC, and being unsatisfied with that I tried to simulate it via telnet with moderate but, in my opinion, insufficient success. I knew that to do it properly would take real hardware but, especially at the time, the options available were beyond my experience so I’d been unable to make use of the available resources. There have been PIC and FPGA based designs, such as several electronic magazine published designs along with R.T. Russell’s Test Card Generator, IMOGen, VBIT and even Alistair Buxton who did it in software and some poking around with video card timings. I also found a random schematic and a snippet of assembly code here, many months ago (the date keeps changing, for some reason), but try as I might I couldn’t make it work. But then I found something new, something I could work with. In the coming weeks, I’ll be documenting my current efforts to bring Teletext back to the masses, or at least those hobbyists, like me, who remember with great fondness this excellent technology, so join me next time to see how I began to bring this thing back to life. m4s0n501 One Response Teletext Revival, Part 2: Making It Work | The New Tech June 29, 2013 [...] This article is a continuation of my series on my attempts to bring teletext back to my TV, you can find the previous part here. [...] Log in to Reply Leave a Reply Cancel Reply You must be logged in to post a comment.