Noise cancellation for the agc or sync separator stages in a television receiver

Claim 1

IN A RECEIVER FOR TELEVISION SIGNALS INCLUDING A VIDEO SIGNAL COMPONENT AND A SYNCHRONIZING SIGNAL COMPONENT OF AN AMPLITUDE EXCEEDING THE PEAK AMPLITUDE OF THE VIDEO SIGNAL COMPONENT, WHICH VIDEO SIGNAL COMPONENT MAY INCLUDE NOISE IMPULSES OF AN AMPLITUDE EXCEEDING THE MAXIMUM AMPLITUDE OF THE SYNCHRONIZING PULSES CONTAINED THEREIN, THE COMBINATION INCLUDING: MEANS INCLUDING A VIDEO DETECTOR FOR DEMODULATING TELEVISION SIGNALS AND PROVIDING A COMPOSITE VIDEO SIGNAL, WHICH COMPOSITE VIDEO SIGNAL INCLUDES SYNCHRONIZING PULSES OF A GIVEN POLARITY AND WHICH PULSES MAY BE ACCOMPANIED BY NOISE IMPULSES OF THE SAME POLARITY; SIGNAL TRANSLATING MEANS FOR APPLYING SAID COMPOSITE VIDEO SIGNAL TO UTILIZATION MEANS; SYNCHRONIZING SIGNAL SEPARATOR CIRCUIT MEANS INCLUDING A FIRST TRANSISTOR HAVING INPUT AND OUTPUT ELECTRODES; TIME CONSTANT NETWORK MEANS INCLUDING SERIES CAPACITANCE MEANS COUPLING SAID INPUT ELECTRODE OF SAID FIRST TRANSISTOR TO SAID SIGNAL TRANSLATING MEANS TO SUPPLY SAID COMPOSITE VIDEO SIGNAL THERETO, WITH SAID TIME CONSTANT NETWORK MEANS BIASING SAID FIRST TRANSISTOR TO PERMIT CONDUCTION THEREOF ONLY BY SIGNASLS EXCEEDING THE MAXI MUM AMPLITUDE FO THE VIDEO COMPONENT OF SAID COMPOSITE VIDEO SIGNAL, AND WITH SAID TIME CONSTANT NETWORK MEANS RETAINING A CHARGE TO REVERSE BIAS SAID FIRST TRANSISTOR NONCONDUCTING FOR PORTIONS OF THE COMPOSITE VIDEO SIGNAL NOT EXCEEDING SAID MAXIMUM LEVEL OF THE VIDEO COMPONENT OF SAID COMPOSITE VIDEO SIGNAL; A SECOND TRANSISTOR HAVING INPUT, OUTPUT AND COMMON ELECTRODES; MEANS INCLUDING A POTENTIAL SUPPLY CONNECTED TO SAID COMMON ELECTRODE FOR BIASING SAID SECOND TRANSISTOR INTO SATURATED CONDUCTION; RESISTANCE MEANS COUPLING THE OUTPUT ELECTRODE OF SAID SECOND TRANSISTOR TO THE SERIES CAPACITANCE MEANS OF SAID TIME CONSTANT NETWORK MEANS; AND CIRCUIT MEANS COUPLING THE INPUT ELECTRODE OF SAID SECOND TRANSISTOR TO SAID SIGNAL TRANSLATING MEANS TO SUPPLY SAID COMPOSITE VIDEO SIGNAL THERETO, WITH NOISE IMPULSES OF SAID GIVEN POLARITY EXCEEDING THE MAXIMUM LEVEL OF SAID SYNCHRONIZING PULSES BY A PREDETERMINED AMOUNT CAUSING SAID SECOND TRANSISTOR TO BECOME NON-CONDUCTING, WHEREBY NOISE CANCELLING IMPULSES ARE COUPLED TO SAID CAPACITANCE MEANS OF SAID TIME CONSTANT NETWORK MEANS WITH A REVERSE POLARITY TO PREVENT NOISE CHARGE-UP THEREOF.