System reference signal insertion circuit - applies to video signal with active and flyback intervals and uses two non:additive signal mixers (NL 21.9.77)

摘要

The video signal reference insertion circuit includes a clamping circuit for clamping the video signal to a reference potential during the fly-back interval. It has also a unit (15) for reference signal generation, which appears during the fly-back interval, and a non-additive signal mixer (12-14, 16, 17) which responds to the clamped video signal and the reference signal, and delivers an output with the reference signal inserted into the video signal fly-back interval. A second non-additive mixer (20-24) responds to a second pick-up signal and has a polarity coding which determines the white field or black field response.