Variable gain control

Claim 1

APPARATUS FOR REPRODUCING SIGNALS THAT HAVE BEEN RECORDED IN A PLURALITY OF RECORDING TRACKS OF DIFFERENT RADII UPON A DISCOID RECORD, COMPRISING MEANS FOR ROTATING SAID RECORD AT A FIXED ANGULAR VELOCITY, WHEREBY SAID TRACKS MOVE AT DIFFERENT LINEAR VELOCITIES PROPORTIONAL TO THEIR RESPECTIVE RADII, A TRANSDUCER FOR PRODUCING FROM SUCH RECORDING TRACKS ELECTRIC SIGNALS HAVING AN AMPLITUDE APPROXIMATELY PROPORTIONAL TO THE LINEAR VELOCITY OF THE RECORDING TRACK, MEANS FOR SELECTIVELY MOVING SAID TRANSDUCER RADIALLY INWARD AND OUTWARD RELATIVE TO SAID RECORD AND THUS INTO ALINEMENT WITH SAID TRACKS SELECTIVELY, A VARIABLE-GAIN AMPLIFIER CONNECTED TO RECEIVE AND TO TRANSMIT SAID SIGNALS, AN AUTOMATIC MEANS SEPARATE FROM SAID AMPLIFIER FOR PRODUCING A BIASING VOLTAGE PROPORTIONAL TO THE INWARD AND OUTWARD MOVEMENT OF SAID TRANSDUCER RELATIVE TO THE PERIPHERY OF SAID DISCOID RECORD, AND MEANS FOR APPLYING SAID BIASING VOLTAGE TO SAID AMPLIFIER FOR DECREASING THE AMPLIFIER GAIN IN PROPORTION TO OUTWARD MOVEMENTS OF THE TRANSDUCER TOWARD THE DISCOID RECORD PERIPHERY AND FOR INCREASING THE GAIN OF SAID AMPLIFIER IN PROPORTION TO THE INWARD MOVEMENTS OF SAID TRANSDUCER ON SAID DISCOID RECORD IN A DIRECTION INWARDLY FROM THE PERIPHERY, WHEREBY THE OUTPUT SIGNALS OF SAID AMPLIFIER ARE SUBSTANTIALLY THE SAME AMPLITUDE INDEPENDENTLY OF THE LINEAR VELOCITY OF MOVEMENT OF EACH OF SAID RECORDING TRACKS RELATIVE TO THE TRANSDUCER.