In the disclosed teletext system, the transmitter station broadcasts data cks data from several channels, the data packs being time multiplexed. Each data pack comprises a prefix signal for causing a teletext receiver either to accept the data packs of a selected channel or to reject data packs from...http://www.google.de/patents/US4213124?utm_source=gb-gplus-sharePatent US4213124 - System for digitally transmitting and displaying texts on television screen
