Abstract: A valve control having a piston movable within a body, inlet outlet and bleed ports in said body, said piston having an opening therethrough with an orifice containing check valve positioned within said opening for permitting fluid to bleed from said outlet to said inlet.

Abstract: A fluid valve operative based on a pressure differential through the utilization of different size pressure receiving piston faces. A first fluid, through pressure on an enlarged piston face, maintains a valve spool so shifted as to allow for a through passage of a second fluid. Upon a blocking of the first fluid, the second fluid, acting on a relatively smaller valve surface, actuates the valve and blocks through passage of the second fluid. The shifting of the valve presents yet a smaller pressure receiving face to the first fluid which, in conjunction with an exhaust port, provides a fail safe lock out requiring manual resetting of the relay.