Abstract: A control system for a cyclic process includes a pulse generator incorporating three rotatable gears for generating pulses. A first gear having n ferromagnetic teeth is mounted on a main generator shaft for generating a train of pulses in a magnetic perception head upon rotation of the main generator shaft, and also mounted on the main generator shaft is a second gear wheel having n + 1 teeth. The second gear wheel drivingly engages with a third gear wheel having n teeth which is mounted for rotation on another shaft, and the second and third gear wheels each carry a ferromagnetic element movement of which past respective further magnetic perception heads causes the generation of a single pulse during each rotation of the second and third gear wheels.