Teletext Technology

 

Teletext Technology

Teletext is an early form of digital information broadcast that delivers text and simple graphics via television signals. Introduced in the 1970s, it was mainly used to provide news, weather, subtitles, sports scores, TV schedules, and other information to viewers without needing the internet.

 How Teletext Works

1. Signal Embedding:

   • Teletext data is transmitted in the vertical blanking interval (VBI) of an analog TV signal.

   • This is the unused portion of the TV broadcast signal between frames.

2. Decoding:

   • A teletext decoder inside the TV extracts and interprets the data.

   • Early TVs needed external adapters; later, decoders were built in.

3. Display:

   • Information is displayed as pages of text and block graphics.

   • Viewers select pages by entering a three-digit code (e.g., 100 for the index).

 Features of Teletext Technology

• Information Pages: Hundreds of pages updated regularly.

• Subtitling (Closed Captioning): A major accessibility feature for the hearing-impaired.

• Navigation Codes: Page numbers allowed simple browsing.

• Low Bandwidth: Efficiently fit text into the broadcast signal.

• Universal Access: No subscription required, only a compatible TV.

Applications

• News and Weather Updates

• Sports Results and Live Scores

• Flight/Travel Information

• Subtitles for TV Programs

• Emergency Alerts

 Decline of Teletext

• With the rise of the internet, mobile apps, and digital TV services, teletext usage declined.

• Many European broadcasters (BBC Ceefax, ORF Teletext, etc.) discontinued teletext in the 2000s–2010s.

• Some countries still maintain digital teletext services integrated into DVB (Digital Video Broadcasting).

 Modern Successors

• Digital Teletext / MHEG-5 (interactive text services in DVB).

• Red Button Services on digital TV.

• Internet-based news and EPGs (Electronic Program Guides).