Utilising unused TV picture frame lines - using supplementary audio transmission and code-responsive interrupt switch

摘要: Unused picture frame lines are exploited for the compressed digital transmission of supplementary audio information in teletext services. The system comprises a data store (UT) and (bt) associated information. former supplies re-coding circuit buffer (VTCO) to be able transmit single burst responsive t.v. line counter (ZZ) causing change-over switch (TtU) connect sender (S) with that (VTCO). Groups frames thus sent out at intervals, there often also empty lines. This unused capacity may utilised transmitting digitised signals bit rate 36 Kbit per second. At subscriber station (T1n) receiver (E) normally feeds into (P) which gives slower d-a converter loudspeaker. input is interrupted when new selected via code (UTt) receive video recirculating (VT Dec).