Hearing aid automatic gain control system

Claim 1

A HEARING AID OF THE TYPE WHICH OPERATES FROM A BATTERY POWER SUPPLY OF NOT OVER ONE AND ONE-HALF VOLTS COMPRISING: A TRANSISTORIZED AMPLIFYING SYSTEM FOR DEVELOPING, IN RESPONSE T RECEIVE ACOUSTIC ENERGY OF VARYING LOUDNESS, AN AMPLIFIED AUDIO SIGNAL REPRESENTATIVE OF SAID ACOUSTIC ENERGY AND HAVING SATURATION AND CUTOFF LEVELS DEFINING A PREDETERMINED OVERLOAD RANGE; AN OUTPUT TRANSFORMER, INCLUDED IN SAID TRANSISTORIZED AMPLIFYING SYSTE, HAVING ONE OUTPUT WINDING FOR CONNECTION TO AN OUTPUT TRANSDUCER AND HAVING A SECOND VOLTAGE STEP-UP OUTPUT WINDING; VOLTAGE DEVELOPING MEANS, INCLUDING A VOLTAGE DOUBLER HAVING A FULL WAVE RECTIFIER FOR PEAK RECTIFYING BOTH THE POSITIVE AND NEGATIVE HALF CYCLES OF SAID AMPLIFIED AUDIO SIGNAL AND ALSO HAVING AN INPUT COUPLED TO SAID SECOND OUTPUT WINDING AND HAVING AN OUTPUT, STORAGE CONDENSER MEANS, AND CHARGING CIRCUITRY FOR SAID STORAGE CONDENSER MEANS COUPLED TO THE OUTPUT OF SAID VOLTAGE DOUBLER FOR CHARGING SAID STORAGE CONDENSER MEANS IN RESPONSE TO AN INCREASE IN LOUDNESS OF SAID INCOMING RECEIVED ACOUSTIC ENERGY TO DEVELOP IN SAID STORAGE CONDENSER MEANS AN AUTOMATIC GAIN CONTROL VOLTAGE HAVING A MAGNITUDE PROPORTIONAL TO THE PEAK-TO-PEAK AUDIO AMPLITUDE AND DETERMINED BY THE INSTANTANEOUS LOUDNESS OF SAID RECEIVED ACOUSTIC ENERGY, SAID CHARGING CIRCUITRY AND STORAGE CONDENSER MEANS COLLECTIVELY ESTABLISHING AN ATTACK TIME OF PREDETERMINED MINIMUM DURATION; DISCHARGING CIRCUITRY FOR DISCHARGING SAID STORAGE CONDENSER MEANS IN RESPONSE TO A DECREASE IN LOUDNESS OF SAID RECEIVED ACOUSTIC ENERGY TO DECREASE THE MAGNITUDE OF SAID AUTOMATIC GAIN CONTROL VOLTAGE; AND MEANS FOR APPLYING SAID AUTOMATIC GAIN CONTROL VOLTAGE TO SAID TRANSISTORIZED AMPLIFYING SYSTEM TO VARY THE GAIN THEREOF IN A DIRECTION TENDING TO MAINTAIN THE OPERATION OF SAID AMPLIFYING SYSTEM WITHIN SAID OVERLOAD RANGE AND TO MAINTAIN THE OUTPUT OF SAID SYSTEM AT A CONSTANT AMPLITUDE IN SPITE OF VARIATIONS IN LOUDNESS OF SAID RECEIVED ACOUSTIC ENERGY, SAID STORAGE CONDENSER MEANS PRESENTING A SUBSTANTIAL LOAD ON SAID AMPLIFYING SYSTEM DURING SAID ATTACK TIME TO PREVENT OVERDRIVING OF SAID AMPLIFYING SYSTEM BEYOND SAID OVERLOAD RANGE UNITL SAID AUTOMATIC GAIN CONTROL VOLTAGE REDUCES THE GAIN OF SAID SYSTEM TO A POINT WITHIN SAID RANGE.