Teletext

Television broadcast signals carried more than just pictures. Between the visible scan lines, there was room for additional data—the vertical blanking interval, a gap originally designed to let cathode ray tubes reset between frames. In the early 1970s, engineers at the BBC and IBA (Independent Broadcasting Authority) in the UK realized this unused bandwidth could carry text and simple graphics to any television with the right decoder chip.

Ceefax launched on BBC television on September 23, 1974, the world's first teletext service. The name combined 'see' and 'facts.' Oracle, the IBA's competing service, followed weeks later on ITV. Users pressed a button on their remote control, entered a three-digit page number, and waited—sometimes several seconds—for the rotating carousel of pages to cycle to their selection. News headlines, weather forecasts, sports scores, TV schedules, and lottery results appeared as blocky text and crude graphics on screens designed for moving images.

The adjacent possible assembled from broadcast engineering and semiconductor advances. Television signals already used the vertical blanking interval for test patterns and synchronization. Encoding text as digital data within this gap required no additional spectrum—the information piggybacked on existing transmissions. Decoder chips, increasingly affordable as integrated circuit costs fell, could be built into televisions or set-top boxes. The BBC's engineering department, with decades of broadcast innovation behind it, possessed the expertise to design the system.

The British context mattered. The BBC and IBA operated as public service broadcasters with mandates to inform, not just entertain. Commercial pressures were muted compared to American networks. The organizations could invest in experimental services that might not generate immediate revenue. Government spectrum allocation gave them control over transmission infrastructure. When Ceefax and Oracle launched, they represented public investment in information access—precursors to the web's democratization of knowledge.

Teletext spread across Europe during the late 1970s and 1980s. Germany's Videotext (1980), France's Antiope (1977), and similar systems appeared in Scandinavia, the Netherlands, and beyond. The World System Teletext standard emerged in 1976, enabling interoperability. By the mid-1980s, teletext-equipped televisions were common in European households, offering a crude but functional information service that predated the internet for ordinary consumers.

The limitations were fundamental. Teletext was one-way—users could only receive, not send. The carousel architecture meant waiting for pages to cycle around, with popular pages repeated more frequently. Resolution was low: 40 columns by 24 rows of blocky characters. Graphics used a 6-block mosaic system that could produce only primitive shapes. Yet within these constraints, teletext served real needs: checking news without waiting for broadcasts, looking up train schedules, following election results in real-time.

Teletext enabled videotex, its two-way descendant that added telephone-line interactivity. The French Minitel system, though technically distinct, built on teletext's demonstration that ordinary people could interact with text-based electronic information services. When the web arrived in the 1990s, it offered everything teletext could do and infinitely more. BBC Ceefax continued until October 2012, finally shut down as digital television eliminated the analog vertical blanking interval that had made it possible. A technology born from unused bandwidth in television signals had given millions their first taste of on-demand electronic information.