Model AFS-477 is a general purpose proving switch with gold contacts suitable for HVAC, Energy Management and DDC (Direct Digital Control) applications. It can 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-477 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 compression ferrule and nut sample line connectors that accept ¼” OD rigid tubing.