Automatic gain control circuit employing variable attenuation balanced diode bridge

Claim 1

AN AUTOMATIC GAIN CONTROL CIRCUIT COMPRISING: FIRST AND SECOND TRANSFORMERS EACH INCLUDING PRIMARY AND SECONDARY WINDINGS; MEANS FOR APPLYING AN INPUT SIGNAL TO THE PRIMARY WINDING OF SAID FIRST TRANSFORMER; A PAIR OF RESISTORS RESPECTIVELY COUPLING OPPOSITE ENDS OF SID SECONDARY WINDING OF SAID FIRST TRANSFORMER TO OPPOSITE ENDS OF SAID PRIMARY WINDING OF SAID SECOND TRANSFORMER; A VARIABLE ATTENTUATOR INCLUDING A BALANCED DIODE BRIDGE HAVING FIRST AND SECOND JUNCTION POINTS BETWEEN THE DIODES THEREOF AT OPPOSITE ENDS OF A FIRST DIAGONAL OF THE BRIDGE AND THIRD AND FOURTH JUNCTION POINTS BETWEEN THE DIODES THEREOF AT OPPOSITE ENDS OF A SECOND DIAGONAL OF THE BRIDGE, SAID FIRST AND SECOND JUNCTION POINTS RESPECTIVELY CONNECTED TO THE ENDS OF SAID PRIMARY WINDING OF SAID SECOND TRANSFORMER; HIGH GAIN AMPLIFYING MEANS COUPLED TO THE SECONDARY WINDING OF THE SECOND TRANSFORMER; A SWITCHING CONTROL TRANSISTOR COUPLED TO THE AMPLIFYING MEANS, HAVING EMITTER, BASE AND COLLECTOR ELECTRODES, SAID EMITTER AND COLLECTOR ELECTRODES BEING COUPLED TO VOLTAGE SOURCES; A VOLTAGE DIVIDER COUPLED TO THE VOLTAGE SOURCES, INCLUDING A VARIABLE RESISTANCE, FOR BIASING THE BASE ELECTRODE OF THE SWITCHING CONTROL TRANSISTOR; A SWITCHING DIODE HAVING AN ANODE AND A CATHODE, SAID CATHODE COUPLED TO THE COLLECTOR ELECTRODE OF THE SWITCHING CONTROL TRANSITOR; A CAPACITOR COUPLED TO THE ANODE OF THE SWITCHING DIODE TO PROVIDE A PEAK DETECTOR; A RESISTANCE CONNECTED IN PARALLEL WITH SAID CAPACITOR AND PROVIDING A TIME CONSTANT NETWORK THEREBY CONTROLLING THE DISCHARGE TIME OF SAID CAPACITOR; A BIAS CONTROL TRANSISTOR HAVING EMITTER, BASE AND COLLECTOR ELECTRODES, THE BASE ELECTRODE BEING COUPLED TO THE TIME CONSTANT NETWOEK, THE COLLECTOR ELECTRODE OF THE BIAS CONTROL TRANSISTOR BEING COUPLED TO SAID THIRD FUNCTION POINT BETWEEN THE DIODES OF THE DIODE BRIDGE; AND MEANS FOR PROVIDING A POTENTIAL TO SAID FOURTH JUNCTION POINT BETWEEN THE DIODES OF THE DIODE BRIDGE.