Abstract: An internal combustion engine with M cylinders having an electronic ignition system, a pistons position sensor having a set of M+1 identical conductive members, which are synchronous with rotation of the engine's crankshaft. M of the conductive members are regularly spaced. Two fixed detectors adjacent the rotating members sense the members and supply identical electrical signals. The detectors are spaced to provide the signals out of phase by an amount that is substantially higher than the maximum ignition advance of the engine. Electronic circuits process the signals from the two detectors, include a first circuit that supplies a synchronization signal for the cycle igniting the engine, and a second circuit, which supplies two representative synchronization signals of the static advance and of the maximum dynamic advance during ignition.