EMERGENCY-SYSTEM-CONTROLLED AIR SHUTOFF VALVE MECHANISM

When the emergency system is switched in, air under pressure is delivered through connection 1, pushing valve spool 2 to the right, overcoming the resistance of helical spring 4 and shutting off inlet port 5 of the main pneumatic system. This air flows through slots in spool 2 and out through port 3.
$3612$SHP,Va$