Model AFS-271 is a general purpose proving switch designed for HVAC and Energy Management 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-271 has a field adjustable set point range of 0.05″ wc to 2.0″ wc. The snap-acting switch has three ¼” 90°quick connect spade terminals. 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.