Chopper demodulator system for direct-record tape recorders

Claim 1

A RECORD-PLAYBACK SYSTEM COMPRISING: (A) AN INFORMATION SIGNAL SOURCE, (B) A REFERENCE VOLTAGE SOURCE, (C) CHOPPER MEANS CONNECTED TO SAID REFERENCE AND SIGNAL SOURCES FOR SYNCHRONOUSLY REVERSEAL CHOPPING SIGNALS FROM THE REFERENCE VOLTAGE AND SIGNAL VOLTAGE SOURCES, (D) TAPE RECORDER MEANS COUPLED TO SAID REFERENCE AND SIGNAL SOURCES FOR RECORDING THE CHOPPED SIGNALS ON SEPARATE CHANNELS OF A MAGNETIC TAPE, (E) PLAYBACK MEANS FOR REPRODUCING SIGNALS RECORDED IN SAID SEPARATE CHANNELS, (F) MEANS FOR ALGEBRAICALLY ADDING THE CHOPPED SIGNALS IN EACH CHANNEL, (G) FIRST MEANS COUPLED TO THE ADDED SIGNALS FOR FULL WAVE RECTIFYING SAID ADDED SIGNALS IN A POSITIVE SENSE, AND (H) SECOND MEANS COUPLED TO THE REVERSAL CHOPPED REFERENCE VOLTAGE CHANNEL FOR FULL WAVE RECTIFYING THE REVERSAL CHOPPED REFERENCE VOLTAGE IN A POSITIVE SENSE, AND (I) MEANS FOR AMPLIFYING THE SEPARATELY RECTIFIED VOLTAGES IN A DIFFERENTIAL AMPLIFIER WHEREBY THE CHOPPED REFERENCE VOLTAGE IN EACH CHANNEL CANCELS AND LEAVES A REPRODUCTION OF THE INFORMATION SIGNAL FROM SAID SIGNAL SOURCE.