Electrically variable resonant circuit controlled by the frequency of a separate pilot input signal

Claim 1

AN ELECTRICALLY TUNABLE FILTER ARRANGEMENT COMPRISING: (A) AN ELECTRICALLY VARIABLE RESONANT CIRCUIT; (D) MEANS FOR PRODUCING AND SUPPLYING TO SAID RESONANT CIRCUIT A TUNING SIGNAL WHICH VARIES IN DISCRETE STEPS FOR THE PURPOSE OF TUNING SAID RESONANT CIRCUIT; (C) MEANS FOR APPLYING A PILOT SIGNAL TO SAID RESONANT CIRCUIT, THE FREQUENCY SPECTRUM OF SAID PILOT SIGNAL BEARING A PREDETERMINED RELATIONSHIP TO THE FREQUENCY TO WHICH THE RESONANT CIRCUIT IS TO BE TUNED; (D) MEANS FOR COMPARING THE OUTPUT OF SAID RESONANT CIRCUIT WITH SAID PILOT SIGNAL AND GENERATING A SIGNAL PROPORTIONAL TO THE RELATIONSHIP BETWEEN THEM; AND (E) MEANS RESPONSIVE TO THE SIGNAL GENERATED BY SAID COMPARING MEANS FOR CONDITIONING SAID TUNING SIGNAL PRODUCING MEANS FOR STEPWISE VARIATION WHEN THE RESONANT FREQUENCY OF RESONANT CIRCUIT IS OUTSIDE A PREDETERMINED VALUE FROM THE DESIRED FREQUENCY, AND FOR MAINTAINING SAID TUNING SIGNAL AT ONE OF THE DISCRETE OUTPUT VALUES OF SAID TUNING SIGNAL PRODUCING MEANS WHEN THE RESONANT FREQUENCY OF SAID RESONANT CIRCUIT IS WITHIN SAID PREDETERMINED VALUE FROM THE DESIRED FREQUENCY.