Electric pulse generating apparatus is provided for the ignition system of an internal combustion engine. Apparatus comprises essentially means for delivering a voltage which is substantially-inversely proportional to the rotating speed of the engine, means for delivering a sawtooth voltage whose leading edge slope is proportional to the rotating speed of the engine, means for comparing these two voltages and delivering - when the voltage substantially-inversely proportional to the speed is lower than at least one value of the sawtooth voltage - pulses for controlling the ignition system of the engine.