Generator for amplitude and frequency modulated low-frequency alternating voltages

Claim 1

A VARIABLE LOW-FREQUENCY SINE WAVE GENERATOR COMPRISING IN COMBINATION: (A) FIRST MEANS FOR GENERATING A SINUSOIDAL VOLTAGE OF RELATIVELY FIXED HIGH FREQUENCY AND VARIABLE AMPLITUDE; (B) SECOND MEANS FOR PROVIDING A TRAIN OF INTERMITTENT TRIGGER SIGNALS OF VARIABLE FREQUENCY; (C) THIRD MEANS ADAPTED TO BE ENERGIZED BY A VARIABLE MAGNITUDE D-C CONTROL SIGNAL FOR VARYING THE AMPLITUDE OF SAID SINUSOIDAL VOLTAGE AS A FUNCTION OF THE CONTROL SIGNAL MAGNITUDE; (D) AN OUTPUT TERMINAL; AND (E) FOURTH MEANS CONNECTED TO SAID OUTPUT TERMINAL FOR SUPPLYING THERETO AN ALTERNATING OUTPUT VOLTAGE SAID FOURTH MEANS INCLUDING PERIODICALLY OPERATIVE SAMPLING MEANS CONNECTED TO SAID FIRST MEANS AND CONTROLLED BY SAID SECOND MEANS FOR PROGRESSIVELY ADJUSTING THE VALUE OF SAID OUTPUT VOLTAGE TO REFLECT THE INSTANTANEOUS MAGNITUDE AND THE POLARITY OF SAID SINUSOIDAL VOLTAGE ON THE INCIDENCE OF SUCCESSIVE TRIGGER SIGNALS, WHEREBY SAID OUTPUT VOLTAGE APPROXIMATES A SINE WAVE THE FREQUENCY OF WHICH IS EQUAL TO THE DIFFERNCE BETWEEN SAID FIXED FREQUENCY AND SAID VARIABLE FREQUENCY AND THE AMPLITUDE OF WHICH DEPENDS ON SAID SINUSOIDAL VOLTAGE AMPLITUDE.