No pilot signal. Inlet air is blocked by poppet C. Piston B slides on the valve stem and is pushed upward if there is any downstream pressure. This opens the exhaust and vents the downstream line.

Pilot signal applied. Pilot air forces piston B downward to close exhaust port. Pilot air also flows past the metering pin, opens the ball check, and slowly pressurizes the outlet line. Pressure is also building up on piston A.

When the pressure on piston A reaches 50% of inlet pressure, the piston is forced downward, opening inlet poppet C. Full inlet pressure now flows freely to the outlet port.

Pilot signal removed. Air above pistons A and B is exhausted through the exhaust port of the remote pilot valve. Air above poppet C forces sliding piston B up so that the main exhaust port is opened and pressurized air is exhausted.