1. AN ELECTRICAL CIRCUIT ENERGIZED BY AN ALTERNATING VOLTAGE SOURCE COMPRISING A FIRST CIRCUIT PORTION INCLUDING A UNIDIRECTIONAL CONDUCTIVE DEVICE; A SECOND CIRCUIT PORTION INCLUDING A SATURABLE REACTOR CONNECTED IN SERIES WITH SAID FIRST CIRCUIT PORTION; A THIRD CIRCUIT PORTION, INCLUDING TWO SERIES CONNECTED IMPEDANCE ELEMENTS, AT LEAST ONE OF WHICH IS VARIABLE, CONNECTED IN PARALLEL WITH ONE OF SAID FIRST AND SECOND CIRCUIT PORTIONS; A TRANSISTOR HAVING A BASE, EMITTER, A COLLECTOR; MEANS CONNECTING SAID BASE TO A POINT INTERMEDIATE SAID SERIES CONNECTED IMPEDANCE ELEMENTS; MEANS CONNECTING SAID EMITTER TO ONE END OF SAID SERIES CONNECTED IMPEDANCE ELEMENTS; AND MEANS CONNECTING SAID COLLECTOR TO THE OTHER END OF SAID SERIES CONNECTED IMPEDANCE ELEMENTS, WHEREBY SAID TRANSISTOR CONTROLS THE CURRENT THROUGH SAID SECOND CIRCUIT PORTION IN RESPONSE TO THE IMMPEDANCE PRESENTED BY SAID IMPEDANCE ELEMENTS WHEN SAID UNIDIRECTIONAL CONDUCTIVE DEVICE IS PRESENTING A HIGH IMPEDANCE TO THE FLOW OF CURRENT.