its initial state after a timed interval which is dependent upon engine speed the length of the output pulse from circuit 42 will determine the number of sparks that will be produced for each opening of the points the output of processing circuit 42 is used to drive gated 34 sparking 34 oscillator 44 this oscillator sets the time spacing between subsequent sparks counter and drive logic 46 counts cycles of this oscillator and in turn is utilized to drive switch 38 in accordance with one optional aspect of the invention counter 46 is utilized to assure that an even number of sparks are provided for each point opening of the engine and thus that spark plug firing current polarity is of a like state in practical spark plugs the sparking voltage is found to be lower when the hotter central electrode of the plug is negative with respect to ground circuitry 46 ensures that the first spark of each group of sparks will have this negative polarity second and subsequent sparks of a series of sparks are easier to produce than the first because there are a large number of ions in the vicinity of the spark gap just after the first spark by counting the sparks produced for each point opening and making this an even number it is assured that the first spark produced is of the negative or preferred polarity in summary then it can be seen that the circuitry in fig4 produces.