Compressed air is supplied from the main to port 1 and, in the position shown, is admitted by spool 6 into port 2, which is connected to the actuator (operating cylinder or device). Port 3 is connected to the internal chamber 4 of the valve, which is connected to the atmosphere through port 5. When compressed (pilot) air is admitted through port 7, piston 8 is shifted to the right and it shifts over spool 6. At this, port 3 is connected to port 1, and port 2 is connected to the atmosphere through chamber 4. To return the spool to its initial position, pilot air is admitted through port 9.
$3682$SHP,FC$