Sound detector for color television

Claim 1

IN A COLOR TELEVISION RECEIVER HAVING COMMON INTERMEDIATE FREQUENCY AMPLIFIER STAGES FOR THE SOUND CARRIER AND THE PICTURE CARRIER OF A RECEIVED COLOR TELEVISION SIGNAL, A DETECTOR CIRCUIT FOR DERIVING SOUND INFORMATION FROM SAID RECEIVED TELEVISION SIGNAL INCLUDING IN COMBINATION, A VACUUM TUBE TRIODE, FIRST NETWORK MEANS COUPLED BETWEEN SAID INTERMEDIATE FREQUENCY AMPLIFIER STAGE AND THE CONTROL GRID OF SAID TRIODE, SAID FIRST NETWORK MEANS SIMULTANEOUSLY APPLYING A PORTION OF SAID SOUND CARRIER AND SAID PICTURE CARRIER TO THE CONTROL GRID OF SAID TRIODE, A FIRST LOW IMPEDANCE DIRECT CURRENT VOLTAGE SOURCE IN SAID RECEIVER, MEANS DIRECT CURRENT CONNECTED BETWEEN SAID FIRST DIRECT CURRENT VOLTAGE SOURCE AND THE ANODE OF SAID TRIODE, WITH THE ANODE VOLTAGE THEREBY APPLIED TO SAID TRIODE OF A LOW VALUE TO PROVIDE A NON-LINEAR TRANSFER CHARACTERISTIC OF SAID TRIODE OVER ITS ENTIRE OPERATING RANGE, A SECOND LOW IMPEDANCE DIRECT CURRENT VOLTAGE SOURCE IN SAID RECEIVER, MEANS DIRECT CURRENT CONNECTED BETWEEN SAID SECOND VOLTAGE SOURCE AND THE CATHODE OF SAID TRIODE, WITH SAID TRIODE BEING THEREBY BIASED NEAR CUTOFF, SECOND NETWORK MEANS COUPLED TO THE ANODE OF SAID TRIODE, SAID SECOND NETWORK MEANS TUNED TO THE DIFFERENCE FREQUENCY BETWEEN SAID SOUND CARRIER AND SAID PICTURE CARRIER TO PROVIDE AN INTERCARRIER SOUND SIGNAL FREQUENCY MODULATED WITH AUDIO INFORMATION, AND MEANS FOR DERIVING SAID AUDIO INFORMATION FROM SAID INTERCARRIER SOUND SIGNAL.