Colour carrier oscillator synchronisation system - has transit time demodulator with series-coupled sync. demodulator

摘要

The oscillator is intended for a decoder operated in the PAL standard system. The transit time demodulator is followed by a (B-Y) and (R-Y) synchronous demodulator. A non-demodulated colour synchronisation signal is applied to the signal input of an (R-Y) synchronous demodulator during the colour synchronisation signal interval, while during the rest of the line period a transit time demodulated chrominance signal, and the voltage level of the demodulated signal at the (R-Y) demodulator output are stored line-for-line. Preferably, the stored voltage levels are used after suitable filtering, for the colour carrier oscillator fine adjustment. A chrominance signal, delayed by a line period, may be once added to the non-delayed chrominance signal, and once subtracted. An electronic switch may be in series with the delay line. It is open during the colour synchronisation signal interval, and is placed in front or behind the delay line.