The Model AFS-442 is a general purpose proving switch designed for package burner, furnace, fuel-burning equipment, HVAC and other Energy Management applications. It may be used to sense positive, negative, or differential air pressure. The plated housing contains a diaphragm, a calibration spring and a snap-acting SPDT switch. The AFS-442 has a field adjustable set point range of 0.05″ wc to 2.0″ wc. The screw terminals are protected by an enclosure that accepts 1/2″ conduit. This switch has an SPDT contact arrangement. It is equipped with two ⅛” – 27 NPT female connectors that accept ¼” OD rigid or semi-rigid tubing.