Control apparatus for a television receiver comprising a back porch keyed agc system

Claim 1

IN A TELEVISION RECEIVER HAVING AN IMAGE-REPRODUCING APPARATUS INCLUDING A TELEVISION PICTURE SIGNAL-TRANSLATING CHANNEL AND AN IMAGE-REPRODUCING DEVICE, CONTROL APPARATUS COMPRISING: SIGNAL SUPPLYING MEANS FOR SUPPLYING AT LEAST THE HORIZONTAL BACK PORCH BLANKING LEVEL OF A TELEVISION PICTURE SIGNAL; FIRST PULSE GENERATING MEANS FOR SUPPLYING PULSES WHOSE PEAK PORTIONS ARE SUBSTANTIALLY IN OVERLAPPING TIME RELATIONSHIP WITH THE SYNCHRONIZING PULSES OF SAID TELEVISION PICTURE SIGNAL; SECOND PULSE GENERATING MEANS FOR SUPPLYING SYNCHRONIZING PULSE-CANCELLING PULSES AND OTHER PULSES WHOSE PEAK PORTIONS ARE IN OVERLAPPING TIME RELATIONSHIP WITH SAID BLANKING LEVEL; MEANS, RESPONSIVE TO SAID SUPPLY SIGNALS AND PULSES, INCLUDING SYNCHRONIZING PULSES APERTURE MEANS, FOR DERIVING A SIGNAL REPRESENTATIVE OF VARIATIONS IN THE AMPLITUDE OF SAID BLANKING LEVEL, SAID APERTURE MEANS FOR PREVENTING THE DERIVING OF SAID SIGNAL FROM SAID SYNCHRONIZING PULSES, SAID APERTURE MEANS RESPONSIVE TO SAID PULSES SUPPLIED FROM SAID SECOND PULSE GENERATING MEANS TO BE INOPERATIVE TO SAID BLANKING LEVEL; AND MEANS FOR UTILIZING SAID DERIVED SIGNAL TO STABILIZE A CHARACTERISTIC OF SAID IMAGE-REPRODUCING APPARATUS.