1. A MAGNETIC AMPLIFIER CIRCUIT COMPRISING A MAGNETIC AMPLIFIER STAGE, A CONTROL WINDING ASSOCIATED WITH SAID STAGE, AN OUTPUT WINDING ASSOCIATED WITH SAID STAGE, A UNIDIRECTIONAL CURRENT CONDUCTING DEVICE AND A CAPACITOR ELECTRICALLY CONNECTED IN PARALLEL WITH SAID DEVICE TO FORM A PARALLEL CIRCUIT ELECTRICALLY CONNECTED IN SERIES WITH SAID CONTROL WINDING AND OPERABLE TO BLOCK DIRECT CURRENT INPUT SIGNALS OF ONE POLARITY TO SAID CONTROL WINDING, PASS DIRECT CURRENT INPUT SIGNALS OF THE OPPOSITE POLARITY TO SAID CONTROL WINDING AND TO ALLOW SAID CONTROL WINDING TO RESPOND TO THE RATE OF CHANGE OF DIRECT CURRENT INPUT SIGNALS.

7. AN ENGINE CONTROL SYSTEM COMPRISING MEANS RESPONSIVE TO THE DEPARTURE OF ENGINE TEMPERATURE FROM A DATUM VALUE TO DERIVE AN ELECTRICAL SIGNAL HAVING POLARITY REPRESENTING THE SENSE OF SUCH DEPARTURE AND A MAGNITUDE REPRESENTING THE MAGNITUDE OF SUCH DEPARTURE, A MAGNETIC AMPLIFIER STAGE, A FIRST UNIDIRECTIONAL CURRENT CONDUCTING DEVICE, A CAPACITOR ELECTRICALLY CONNECTED IN PARALLEL ACROSS SAID DEVICE TO FORM A PARALLEL CIRCUIT, MEANS FOR APPLYING SAID ELECTRIC SIGNAL THROUGH SAID PARALLEL CIRCUIT TO THE INPUT OF SAID MAGNETIC AMPLIFIER STAGE WHEREBY ELECTRIC INPUT SIGNALS OF A SELECTED POLARITY ARE BLOCKED AND SAID STAGE RESPONDS TO THE RATE OF CHANGE OF SAID STAGE INPUT SIGNALS, MEANS RESPONSIVE TO THE OUTPUT OF SAID STAGE TO CONTROL THE FLOW OF FUEL TO THE ENGINE AND A SECOND UNIDIRECTIONAL CURRENT CONDUCTING DEVICE CONNECTED BETWEEN SAID OUTPUT RESPONSIVE MEANS AND THE OUTPUT OF SAID STAGE TO BLOCK OUTPUT SIGNALS CORRESPONDING TO RATE OF CHANGE OF A SELECTED SENSE OF SAID INPUT SIGNALS.