Frequency modulation radio receiver with amplitude responsive squelch

Claim 1

A SUPERHETERODYNE FREQUENCY MODULATION RADIO RECEIVER HAVING PROVISIONS FOR CUTTING OFF THE AUDIO OUTPUT WHEN A VERY STRONG SIGNAL IS RECEIVED, SAID RECEIVER INCLUDING IN COMBINATION, AN INTERMEDIATE FREQUENCY AMPLIFIER CIRCUIT, A LIMITER CIRCUIT COUPLED TO SAID INTERMEDIATE FREQUENCY AMPLIFIER CIRCUIT, A DETECTOR CIRCUIT COUPLED TO SAID LIMITER CIRCUIT FOR DERIVING AUDIO FREQUENCY SIGNALS FROM THE LIMITED INTERMEDIATE FREQUENCY SIGNALS, AUDIO AMPLIFIER MEANS CONNECTED TO SAID DETECTOR CIRCUIT INCLUDING A FIRST TRANSISTOR FOR AMPLIFYING DETECTED AUDIO FREQUENCY SIGNALS, A SQUELCH CIRCUIT INCLUDING A SECOND TRANSISTOR COUPLED TO SAID FIRST TRANSISTOR, SAID SECOND TRANSISTOR BEING CONNECTED TO SAID FIRST TRANSISTOR TO BIAS THE SAME TO CUT OFF IN RESPONSE TO CONDUCTION OF SAID SECOND TRANSISTOR, SAID LIMITER CIRCUIT INCLUDING A PORTION PROVIDING DETECTED NOISE SIGNALS, SAID SQUELCH CIRCUIT INCLUDING FILTER MEANS CONNECTING SAID PORTION OF SAID LIMITER CIRCUIT TO SAID SECOND TRANSISTOR FOR APPLYING DETECTED NOISE SIGNALS ABOVE A PREDETERMINED FREQUENCY TO SAID SECOND TRANSISTOR TO RENDER THE SAME CONDUCTIVE, AND FREQUENCY SELECTIVE MEANS INCLUDING CAPACITOR MEANS CONNECTED BETWEEN THE OUTPUT OF SAID INTERMEDIATE FREQUENCY AMPLIFIER CIRCUIT AND SAID SECOND TRANSISTOR, SAID FREQUENCY SELECTIVE MEANS COUPLING SIGNALS FROM SAID INTERMEDIATE FREQUENCY AMPLIFIER CIRCUIT TO SAID SECOND TRANSISTOR TO RENDER THE SAME CONDUCTIVE IN RESPONSE TO SIGNALS IN SAID INTERMEDIATE FREQUENCY AMPLIFIER CIRCUIT WHICH REACH A PREDETERMINED LEVEL AND THEREBY CUT OFF SAID FIRST TRANSISTOR.