Abstract: A main poppet body of a logic valve receives inlet pressure at first and second ends. A flow-restricting orifice between the first and second ends produces a differential pressure between the two ends when inlet fluid is permitted to flow from the second end. The main poppet body is normally resiliently seated against a seat. A pilot poppet body, movable in the main poppet body, seats against a seat in the main poppet body. The pilot poppet body, when sealed to its seat, seals the fluid at the second end of the main poppet body from flowing. Thus, equal pressures exist at opposed ends of the main poppet body, and the main poppet body remains in its sealing position. An external source of controllable pilot pressure acts on the pilot poppet body to unseal it from its seat. This permits a flow of inlet fluid from the second end of the main poppet body, and produces a pressure reduction at the second end.