Frequency modulated crystal oscillator

Claim 1

IN A SIGNAL GENERATING APPARATUS, AN OSCILLATOR COMPRISING A PAIR OF ELECTRON DISCHARGE DEVICES EACH HAVING AN ANODE, A GRID AND A CATHODE; POWER-SUPPLY MEANS PROVIDING A POTENTIAL DIFFERENCE BETWEEN EACH CATHODE AND ITS ASSOCIATED ANODE; TWO CATHODE-ANODE OSCILLATORY CIRCUITS CONNECTED RESPECTIVELY WITH SAID DEVICES; A COUPLING CIRCUIT BETWEEN THE ANODE OF ONE DISCHARGE DEVICE AND THE GRID OF THE OTHER DISCHARGE DEVICE; AN OUTPUT CIRCUIT CONNECTED TO THE ANODE OF THE SAID OTHER DISCHARGE DEVICE; A CATHODE COUPLING CIRCUIT HAVING IN SERIES A PIEZO-ELECTRIC CRYSTAL DIRECTLY COUPOED THEREIN, SAID COUPLING CIRCUIT BEING CONNECTED BETWEEN THE CATHODES OF SAID DEVICES; AN INPUT CIRCUIT CONNECTED TO THE SAID CATHODE COUPLING CIRCUIT; A CONDUCTIVE CRYSTAL DEVICE COMPRISING A PAIR OF TRANSISTORS SERIES CONNECTED BACK-TO-BACK, SAID DEVICES BEING CONNECTED IN THE SAID CATHODE COUPLING CIRCUIT AND CONSTITUTING A VARIABLE IMPEDANCE THEREIN, SAID INPUT CIRCUIT BEING CONNECTED TO FEED A SIGNAL TO THE SAID CONDUCTIVE CRYSTAL DEVICE WHEREBY THE OSCILLATOR PRODUCES A FREQUENCY-MODULATED SIGNAL WHEN A SUITABLE AUDIO SIGNAL IS APPLIED TO THE SAID INPUT CIRCUIT.