Valve control for a combustion engine

The valve control uses camshafts (11,12) for operation of the i.c. engine gas changing valves (7,8), with one or more valves having a stroke which is altered via a switch element (15) having a switching time which is dependent on the engine revs and detected from the rotary oscillation of the camshaft, which is processed to provide a function signal for controlling the hydraulic system of the switch element.