Abstract: In a pressurized operated actuator (1) for stepwise regulation of valves between at least three distinct positions, one end-wall has been removed and replaced with an auxiliary actuator (19) having a piston (21) whose piston area exceeds the sum of the areas of the conventional pistons (5 and 6) of the firstmentioned actuator. The piston (21) of the auxiliary actuator has a piston rod (22) which extends into the cylinder chamber (2a) of the actuator. Its stroke equals half the length of the stroke of the rods (7 and 8) of two conventional pistons (5 and 6). The firstmentioned piston rod (22) limits the movement of the pistons (5 and 6) of the actuator in a direction away from one another. In this way, there can be obtained a distinct intermediate position for the rotary settings of the actuator.