HOW TELETEXT WORKED
Teletext was a marvel of engineering. It used spare capacity in television broadcasts to transmit data - a solution so elegant it worked for nearly 40 years.
THE VERTICAL BLANKING INTERVAL
Television pictures are made of horizontal lines. Between each frame, there's a brief pause called the vertical blanking interval (VBI). Engineers realised this "empty" time could carry data. Teletext packets were inserted into lines 7-22 and 320-335.
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.
THE WAITING GAME
Because pages cycled in sequence, you had to wait for your page to come around. This explained the "Please wait" messages. A typical cycle took 25 seconds for 100 pages. PAGE 100 (news) was broadcast more frequently for faster access.
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). Characters were rendered using the MODE7 character set, giving teletext its distinctive blocky look.
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. The limitations bred creativity.
RELIVE THE NOSTALGIA
QFAX brings back the teletext experience for modern football fans. Live scores on PAGE 316, Vidiprinter on PAGE 350, and the daily Badger game on PAGE 393. Download now and step back in time.
