Defined-Format Teletext Moves to Higher Levels of Display and Yet Fulfils ITS Promise of Compatibility with First Generation Decoders

This paper discusses how the World System Teletext specification is fully compatible with the higher levels of display defined in the new CEPT Videotex 'presentation layer' standard. Careful design of transmission coding results in a system that is both efficient and rugged and yet permits full downwards compatibility with the many first-generation World System Teletext decoders that are installed throughout the world.