comprised of an inductor 101 and a resistor 102 which removes noise spikes and harmonics from the monitor input signal the output of the filter 10 having a period t1 waveform a of fig3 is coupled to a comparator 110 of the gate generator 11 the gate generator 11 is comprised of the comparator 110 which is coupled to a j k flip flop 111 the output q of the j k flip flop 111 is coupled to a first d type flip flop 112 which in turn is coupled to a second d type flip flop 113 both of which are clocked by clock signals from oscillator 22 the output q of the first d type flip flop 112 and the output q of the second d type flip flop are coupled to a nand gate 114 the output of the nand gate 114 yielding the gating signal comparator 110 converts the sine wave signal to a square wave waveform b of fig3 which also has a period of t1 j k flip flop 111 which performs a divide by two operation is triggered by each successive negative edge of waveform b and outputs a signal having a period t2 which is twice the period of the input waveform waveform c of fig3 therefore the period of the waveform c of fig3 corresponds to two complete cycles of the monitor input or generator power the effect of a one cycle disturbance or a single distorted waveform from the generator is thus somewhat diminished if a compensating distortion occurs during the next half cycle the output of j k flip flop 111 is coupled to the first d type flip flop 112 which is set by the.