Derivation of sub-carrier oscillator control voltage from synchronous detectors

Claim 1

IN A SYNCHRONIZING SYSTEM FOR COLOR TELEVISION RECEIVERS UTILIZING COLOR SIGNALS: A FIRST AND SECOND DEMODULATOR STAGE SELECTIVELY RESPONSIVE TO TWO DIFFERENT RECEIVED COLOR SIGNALS, A LOCAL OSCILLATOR PROPORTIONED TO GENERATE SIGNALS AT A SYNCHRONOUS SUBCARRIER FREQUENCY, MEANS INCLUDING CIRCUIT CONNECTIONS FROM SAID OSCILLATOR TO SAID FIRST AND SECOND DEMODULATOR STAGES TO PROVIDE SUBCARRIER FREQUENCY SIGNALS THERETO TO EFFECT THE DEMODULATION OF RECEIVED COLOR SIGNALS, AN ADDER CIRCUIT COUPLED TO SAID FIRST AND SECOND DEMODULATION STAGES INCLUDING MODIFYING MEANS PROPORTIONED TO MODIFY THE AMPLITUDE OF THE DEMODULATED COLOR SIGNALS BY RESPECTIVE PREDETERMINED RATIOS SUBSTANTIALLY EQUAL TO THE COSINE OF THEIR PREDETERMINED PHASE ANGLE TO THE PHASE OF THE SYCHRONIZING SUBCARRIER, MEANS FOR DETECTING THE ADDER-MODIFIED SIGNALS FOR AN UNBALANCED SIGNAL DETERMINING A CORRESPONDING PHASE ERROR IN THE LOCALLY-GENERATED SUBCARRIER SIGNALS RELATIVE TO REQUISITE SYNCHRONOUS DEMODULATION OPERATION OF SAID DEMODULATOR STAGES, AND REACTANCE MEANS IN CIRCUIT WITH SAID OSCILLATOR RESPONSIVE TO THE DETECTED UNBALANCED SIGNALS FOR DIRECTLY CHANGING THE PHASE OF THE LOCALLY-GENERATED SUBCARRIER SIGNALS AND ELIMINATE ITS SAID PHASE ERROR; SAID ADDER CIRCUIT HAVING FIRST AND SECOND RESISTIVE BRANCHES; A FIRST TERMINAL OF EACH OF SAID BRANCHES BEING CONNECTED IN COMMON; THE REMAINING TERMINALS OF SAID RESISTIVE BRANCHES BEING CONNECTED RESPECTIVELY, TO THE OUTPUTS OF SAID FIRST AND SECOND DEMODULATOR STAGES; THE COMMON TERMINAL BETWEEN SAID RESISTIVE BRANCHES BEING CONNECTED TO SAID REACTANCE MEANS.