Alternating current frequency sensing and indicating circuit

Claim 1

A FREQUENCY SENSING AND INDICATING CIRCUIT FOR AN ALTERNATING CURRENT SYSTEM COMPRISING A SATURABLE CORE, SENSING MEANS RESPONSIVE TO THE FREQUENCY OF SAID ALTERNATING CURRENT SYSTEM FOR CHANGING THE FLUX LEVEL IN SAID CORE IN ONE DIRECTION AN AMOUNT PROPORTIONAL TO THE FREQUENCY OF SAID SYSTEM, RESETTING MEANS FOR CHANGING THE FLUX LEVEL IN SAID CORE IN THE OTHER DIRECTION TO A PREDETERMINED LEVEL, SAID SENSING MEANS AND SAID RESETTING MEANS ALTERNATELY AND SUCCESSIVELY ACTING ON SAID CORE AND OUTPUT MEANS FOR PROVIDING A CHARACTERISTIC OUTPUT SIGNAL WHEN THE FLUX LEVEL OF SAID CORE IS CHANGED A PREDETERMINED AMOUNT FROM SAID PREDETERMINED RESET LEVEL BY SAID SENSING MEANS, IN COMBINATION WITH A MONOSTABLE PULSE AMPLIFIER AND RELAY CONTROL CIRCUIT COMPRISING AN OUTPUT RELAY ENERGIZABLE IN RESPONSE TO THE OCCURRENCE OF SAID CHARACTERISTIC OUTPUT SIGNAL AND MEANS RESPONSIVE TO SAID CHARACTERISTIC OUTPUT SIGNAL FOR MAINTAINING SAID RELAY ENERGIZED FOR A PREDETERMINED PERIOD OF TIME AFTER THE OCCURRENCE OF SAID CHARACTERISTIC OUTPUT SIGNAL.