A hydraulic or pneumatic actuator wherein {HEAD ~ the movement} of {TAIL ~ the power transfer shaft} is controlled by a movable vent 
A hydraulic or pneumatic actuator wherein { HEAD ~ the movement } of { TAIL ~ the power transfer shaft } is controlled by a movable vent
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH