Abstract: A photo-electronic internal combustion ignition system in which a shutter rotated by the distributor shaft of the engine alternately supplies and cuts light from a photodiode to a photo-electric pickup. The circuit is devised to produce an exceedingly rapid cut-off of current to the engine induction coil, and for this purpose an amplifier following the pickup has a connection to the photo-diode which as soon as the pickup receives a predetermined minimum amount of light via the shutter, momentarily pulses the photo-diode so that the latter produces a short flash of high intensity light. Induction coil cut-off occurs when the photo-diode receives this light flash.