Liquid level gauge

Claim 1

AN ELECTRONICALLY OPERATED GAUGE FOR AUTOMATICALLY INDICATING THE LEVEL OF LIQUID IN A CONTAINER, SAID GAUGE COMPRISING: (A) OSCILLATOR MEANS INCLUDING A TUNED RESONANT CIRCUIT FOR PRODUCING A VARIABLE FREQUENCY OUTPUT SIGNAL, (B) PROBE MEANS ADAPTED TO MOUNT IN SAID CONTAINER AND PROVIDED TO VARY THE OPERATING FREQUENCY OF SAID OSCILLATOR IN RESPONSE TO CHANGES IN CONTAINER LIQUID LEVEL, SAID PROBE INCLUDING A VARIABLE CAPACITOR COMPRISING SAID CONTAINER, SAID LIQUID AND AN INSULATED SENSING ELEMENT, (C) FIRST CIRCUIT MEANS FOR OPERATIVELY CONNECTING SAID PROBE TO SAID RESONANT CIRCUIT, (D) SECOND CIRCUIT MEANS FOR TRANSLATING THE FREQUENCY OF SAID OSCILLATOR OUTPUT SIGNAL TO A SUBSTANTIALLY LOWER FREQUENCY SIGNAL, (E) FILTER MEANS FOR TRANSLATING FREQUENCY VARIATIONS IN SAID LOWER FREQUENCY SIGNAL TO AN INDICATOR CONTROL SIGNAL HAVING CORRESPONDING AMPLITUDE VARIATIONS, (F) AND MEANS RESPONSIVE TO SAID CONTROL SIGNAL FOR INDICATING THE AMPLITUDE THEREOF.