Phase shifting circuit for fm stereo receiver

Claim 1

IN A FREQUENCY-MODULATION STEREO MULTIPLEX RECEIVER WHEREIN STEREOPHONIC SOUND IS REPRODUCED IN RESPONSE TO RECEIVED COMPOSITE STEREO MULTIPLEX SIGNAL INCLUDING A MODULATED SUBCARRIER CONVEYING AUDIO INFORMATION AND A PILOT SIGNAL CONVEYING PHASING INFORMATION, THE COMBINATION COMPRISING: MEANS FOR RECEIVING THE COMPOSITE STEREO MULTIPLEX SIGNAL; MEANS COUPLED TO THE RECEIVING MEANS FOR GENERATING REFERENCE OSCILLATIONS HAVING A FREQUENCY SUBSTANTIALLY EQUAL TO THE CENTER FREQUENCY OF THE SUBCARRIER; DEMODULATING MEANS COUPLED TO THE RECEIVING MEANS FOR RECOVERING THE AUDIO INFORMATION FROM THE MODULATED SUBCARRIER IN RESPONSE TO THE APPLICATION THERETO OF THE REFERENCE OSCILLATIONS; THE REFERENCE OSCILLATION GENERATING MEANS INCLUDING A PARALLEL RESONANT INDUCTOR-CAPACITOR TANK CIRCUIT RESPONSIVE TO A SIGNAL DERIVED FROM THE PILOT SIGNAL AND TUNED TO A FREQUENCY OF N TIMES F, WHERE N IS AN INTEGER AND F IS THE PILOT SIGNAL FREQUENCY, A RESISTOR AND A SECOND CAPACITOR CONNECTED IN SERIES WITH ONE ANOTHER, THIS SERIES COMBINATIOIN BEING CONNECTED BETWEEN FIRST AND SECOND SPACED APART POINTS ON THE TANK CIRCUIT INDUCTOR, CIRCUIT MEANS RESPONSIVE TO THE SIGNAL APPEARING BETWEEN THE JUNCTION OF THE RESISTOR AND THE SECOND CAPACITOR AND A POINT ON THE TANK CIRCUIT INDUCTOR INTERMEDIATE THE FIRST AND SECOND POINTS FOR DEVELOPING THE REFERENCE OSCILLATIONS SUPPLIED TO THE DEMODULATING MEANS, AND MEANS FOR VARYING THE IMPEDANCE VALUE OF ONE OF THE RESISTOR AND THE SECOND CAPACITOR FOR SHIFTING THE PHASE OF THE REFERENCE OSCILLATIONS.