Automatic gain control circuit with fast change of time constant

Claim 1

IN AN AUTOMATIC-GAIN-CONTROL CIRCUIT HAVING A LONGTIME CONSTANT FILTER INCLUDING A FILTER CAPACITOR, A GAIN CONTROL CONDUCTOR CONNECTED TO SAID LONG-TIME CONSTANT FILTER, A RECTIFIER HAVING ITS OUTPUT CONNECTED TO SAID LONG-TIME CONSTANT FILTER, RADIO-FREQUENCY RECEIVING MEANS CONNECTED TO THE INPUT OF SAID RECTIFIER, THE GAIN OF SAID RADIO-FREQUENCY MEANS BEING CONTROLLED BY APPLICATION OF VOLTAGE FROM SAID FILTER TO SAID GAIN CONTROL CONDUCTOR; MEANS FOR MOMENTARILY DISCHARGING THE CONTROL VOLTAGE ON SAID FILTER CAPACITOR COMPRISING, DIFFERENTIATING MEANS, MEANS FOR APPLYING RECTIFIED UNFILTERED OUTPUT FROM SAID RADIOFREQUENCY RECEIVING MEANS TO SAID DIFFERENTIATING MEANS, SWITCHING MEANS HAVING A PAIR OF SWITCHING ELEMENTS NORMALLY PROVIDING AN OPEN CIRCUIT THEREBETWEEN AND A CONTROL ELEMENT FOR CONTROLLING THE CONDUCTIVITY BETWEEN SAID SWITCHING ELEMENTS, SAID SWITCHING ELEMENTS BEING CONNECTED IN PARALLEL WITH SAID FILTER CAPACITOR, IMPULSE MEANS HAVING AN OUTPUT CIRCUIT CONNECTED TO SAID CONTROL ELEMENT OF SAID SWITCHING MEANS AND AN INPUT CONNECTED TO SAID DIFFERENTIATING MEANS, AND SAID IMPULSE MEANS OPERATING IN RESPONSE TO THE SIGNAL LEVEL AT THE OUTPUT OF SAID RADIO-FREQUENCY RECEIVING MEANS DECREASING FASTER THAN A PREDETERMINED RATE FOR MOMENTARILY APPLYING AN OPERATING VOLTAGE TO SAID CONTROL ELEMENT OF SAID SWITCHING MEANS, SAID SWITCHING MEANS OPERATING IN RESPONSE TO THE APPLICATION OF SAID OPERATING VOLTAGE TO COMPLETE A LOW-RESISTANCE CIRCUIT BETWEEN SAID SWITCHING ELEMENTS FOR MOMENTARILY SHORT-CIRCUITING SAID FILTER CAPACITOR.