Abstract: A system for supplying pressurized fluid from a pressure source to a fluid-operated power device comprises an actuator, a sole first pressure conduit leading from the source to the actuator and at least two second pressure conduits leading from the actuator to the power device. The actuator comprises a cylinder and a piston arranged for simultaneous reciprocation and rotation in the cylinder. The reciprocation of the piston is effected by the fluid pressure introduced periodically into the cylinder through the first pressure conduit. The rotation of the piston is effected by the cooperation of a pin affixed to the cylinder wall with a helically extending groove in the cylindrical piston face.