Single Acting Air Lock Relay is used for locking air in chamber of Single Acting/Spring Loaded cylinders or Diaphragm Actuator in case of an air supply failure. Whenever the supply pressure falls below the set value thereby keeping the actuator instay-put condition. The supply pressure connected to the signal port is sensed by the spring loadeddiaphragm and the thrust developed enable the valves to open thereby air enteringthrough the IN port get connected to the output line of the cylinder chamber. The cut off setting is adjustable and can be done by adjusting the screwand locknut.