Title: Interference protected electronic ignition system for an internal combustion engine

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Abstract: To eliminate the effects of disturbances, noise and interference in the signal derived from a speed-dependent signal generator coupled to the engine on the threshold response level of a threshold switch which, upon sensing a leading flank of the signal, causes a controlled transistor switch to turn ON to pass current through an ignition coil and, upon sensing the trailing flank of the signal, turns the switch OFF to induce an ignition pulse, a supervisory circuit is connected to the threshold switch which provides a bias voltage thereto so that the threshold switch will accurately and reliably respond to the trailing flank of the signal from the signal generator even in the presence of noise and interference voltages at a predetermined angular position of the crankshaft of the engine--absent a shift in the relative angular position of the signal from the signal generator and the crankshaft of the engine--to prevent failure of generation of an ignition pulse, or untimely, uncontrolled generation thereof. The supervisory circuit may include a control charge capacitor providing a bias voltage or, for example, a Schmitt trigger set to respond at different threshold levels of the threshold switch and, upon such response, to provide a bias voltage thereto, thus causing the threshold switch to respond upon response of the Schmitt trigger even in the presence of signal disturbances.


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