VCR adapted for either PAL or SECAM transmissions - has separate chrominance circuits, and switchable frequency converter with bistable for interconnecting appropriate circuits

摘要

The appts. comprises chrominance circuits (3,13, 15-18,20,23,2-12), for the two systems, PAL and SECAM colour suppression circuits (26,25), and a frequency converter circuit (6) which is switchable between the two systems. A bistable switch (30) has a control input connected to a low frequency generator (31) and two other inputs, a set 1 (28) and set 0 (29), connected respectively to the SECAM and PAL colour suppression circuit outputs. The output of the bistable controls a number of invertors (4,21,24) which switch the PAL or SECAM circuits into the signal path, as required. Normally the bistable switches between the circuits at the generator frequency, but an incoming signal is identified by the corresponding colour suppression circuit which holds the bistable in the correct switched mode.