Abstract: A fluid pressure servo detent mechanism for controlling movement of a piston within a cylinder including one-way inlet and outlet valves for controlling the fluid pressure within the cylinder with linkage means interconnecting the inlet and outlet valves and the moveable piston for simultaneously actuation thereof. A control or sensing rod is carried by the piston for movement therewith to provide a control element for articles to be controlled or to sense the position of the piston and the flow of fluid or receipt of pressure to the outlet may be utilized to determine the position of the piston and as a signal to additional equipment.