Low pass supply filter for electronic ignition - has two series coils on one core followed by etched film comb capacitor

The low pass filter is for high frequency suppression of the power feed to a digitally operated electronic ignition circuit as used in internal combustion engines. The low pass filter comprises two induction coils (W1,W2) wound on a common core (K), with one coil in each leg (11,12) of the supply to the ignition circuit controlling microprocessor (P), and a low capacitance capacitor (C3) across the ends of both coils (W1,W2) on the microprocessor side. The capacitor (C3) is an etched, comb structure flat bed, thick film unit designed for minimum intrinsic inductance so that the low pass filter has a very high cut off frequency.