chamber passage 132 is in communication with the diffuser 93 with the valve piston 104 positioned toward the large end the air chamber passage 128 is in communication with the diffuser 92 thus with the valve piston 104 positioned toward the small end pressurized air is provided to the air chamber 38 and the air chamber 40 is opened to exhaust the reverse is true with the valve piston 104 at the other end by reciprocating the valve piston 104 the pump is driven to reciprocate as well to reciprocate the valve piston 104 the differential areas of the two ends of the valve piston 104 are employed with reference to fig7 the inlet passage 124 communicates with a passageway 140 which as seen in fig8 communicates with a passage 142 extending through the valve cylinder 78 to the small end of the valve piston 104 this communication between the small piston 120 and the inlet 122 is always open also associated with the inlet passage 124 is a passageway 144 as best seen in fig7 this passageway 144 extends to a passage 146 extending through the actuator housing 42 to the second guideway 60 as best seen in fig1 the passage 146 is controlled by the seal 72 as the pilot shifting shaft 62 moves from one extreme position to the other the seal 72 crosses the passage 146 to provide communication to the axial passage 75 between the seals 70 and 72 this axial passageway communicates the.