THE QUICK RELEASE VALVE HAS 3 PORTS AS SHOWN IN THE ASSEMBLY VIEW.  AIR PRESSURE ENTERING THE IN PORT FORCES THE DIAPHRAGM TO SEAL THE EXHAUST PORT AND OPEN A DIRECT PASSAGE BETWEEN THE IN AND OUT CYLINDER PORT.  WHEN AIR PRESSURE AT THE OUT PORT IS REDUCED, AND THE PRESSURE IS SLIGHTLY GREATER AT THE OUT PORT, THE DIAPHRAGM IS FORCED AGAINST THE IN PORT.  WITH THE IN PORT SEALED OFF, A DIRECT PASSAGE IS OPENED BETWEEN THE OUT PORT AND THE EXHAUST PORT, ALLOWING THE OPERATED DEVICE TO VENT QUICKLY.