HOW TELETEXT WORKED
Teletext was a marvel of engineering, it really was. It used spare capacity in television broadcasts to transmit data: a solution so elegant it worked for nearly 40 years. I think people underestimate how clever this was.
THE VERTICAL BLANKING INTERVAL
So television pictures are made of horizontal lines, right? Between each frame, there's a brief pause called the vertical blanking interval, the VBI. Engineers realised this "empty" time could carry data. Teletext packets were inserted into lines 7-22 and 320-335. Genius, really.
DATA PACKETS
Each teletext page was divided into packets of 45 bytes. A complete page required 24 packets: one per row. The system continuously cycled through all pages, broadcasting each one in turn. Your TV's decoder would capture and store the page you requested. All happening in the background, obviously.
THE WAITING GAME
Because pages cycled in sequence, you had to wait for your page to come around. This explained those "Please wait" messages we all remember. A typical cycle took 25 seconds for 100 pages. PAGE 100, the news, was broadcast more frequently for faster access. Smart thinking, that.
THE 40x25 GRID
Each page consisted of a 40-column, 25-row grid. Only 7 colours were available: white, red, green, yellow, blue, magenta, and cyan, plus black, obviously. Characters were rendered using the MODE7 character set, giving teletext its distinctive blocky look. Iconic, really.
THE GRAPHICS
Teletext graphics used block characters: each character cell could be divided into a 2x3 grid of "sixels." Clever designers created surprisingly detailed images within these constraints. For me, that's the thing: the limitations bred creativity. People did amazing things with so little to work with.
RELIVE THE NOSTALGIA
QFAX brings back the teletext experience for modern football fans. Live scores on PAGE 316, Vidiprinter on PAGE 350, and On This Day on PAGE 381. Download now and step back in time.
