Abstract

In an ignition system for an internal combustion engine, positive half cycles of an output of the exciter coil are used as the ignition energy. A signal coil outputs a maximum advance angle side signal whose magnitude exceeds a threshold at the maximum advance angle position and a minimum advance angle side signal whose magnitude exceeds a threshold at the minimum advance angle position. An ignition timing control circuit is responsive to a maximum advance angle position indicating pulse derived from the maximum advance angle side signal and a minimum advance angle position indicating pulse derived from the minimum advance angle side signal for producing an ignition signal. The exciter coil and the signal coil have such a phase relation that the minimum advance angle side signals are produced during the negative half cycles of the exciter coil when the engine is rotating forward, and are produced during the positive half cycles of the when the engine is rotating backward. A bypassing switch bypasses the minimum advance angle position indicating pulse away from the ignition timing control circuit during the positive half cycles, so as to prevent production of the ignition signal when the engine is rotating backward.