the portion of the voltage voa that makes up the signal voc and thus change the afa that is applied to the firing of the spark plug for a given period of the mrs if the idl signal is at a logical value of 1 the output voc is a result of the described circuit configuration called continuous advance set circuit the described continuous advance set circuit changes the effective afa at which the spark plug is fired in a continuous function as opposed to a step function the voltage vod is buffered by operational amplifier ob by use of the potentiometer ri the voltage value of vod which causes the output of the voltage comparator oi to change state can be set the output of the d type flip flop fi is updated on the rising edge of the signal clk if the signal idl is of a logical value 1 then the period of the mrs is below that of the set value voltage comparator a2 and its function is called the spark plug firing time calculator spftc the output of spftc is called the afa signal afas the rising edge of the afas marks the point in time where the spark plug will be fired at if the signal idl is of a logical value of 1 the time difference between the rising edge of the afas and the rising edge of the mrs is the afa at which the spark plug is fired the afas.