Ignition system for an internal combustion engine

Claim 1

An ignition system for an internal combustion engine which system includes a power supply and an ignition circuit including an ignition coil having a primary coil portion connected to said power supply and a secondary coil portion connected to at least one ignition plug, said ignition plug disposed within an operating chamber of an engine, a contact breaker to be operated at the ignition time intervals at which ignition is expected for normal operation of the engine, and said contact breaker is connected to said primary coil portion, said ignition system characterized by a triggering signal generator to generate a triggering signal each time said contact breaker is operated; a frequency divider to divide said triggering signal from said triggering signal generator so as to produce a divided signal with the frequency of 1-n times the frequency of said triggering signal wherein n is 2 or 4; an overriding means to periodically override said ignition circuit in response to said divided signal, so that ignition of the engine is caused to fail periodically; and means to allow the operation of said overriding means responsive to conditions requiring failure of ignition of the operating chamber, said overriding means comprising first semiconductor switching means connected in parallel to said primary coil portion of said ignition coil whereby the primary voltage across said primary coil portion is short-circuited when said semiconductor switching means is conductive, and second semiconductor switching means to prevent said first semiconductor switching means from being triggered when said second semiconductor switching means is conductive, said frequency divider arranged so that it permits said second semiconductor switching means to be conductive when it outputs said divided signal.