Series PQ switches are designed for use with air or non-corrosive gas applications which require extremely low actuation points. Large nylon reinforced Buna-N diaphragm combines consistent operation with broad application compatibility. Special magnetic mercury switches assure long term reliability on either AC or DC circuits. Two basic styles are available with single or two stage operation. Both versions have setpoints adjustable over the entire range. The two stage models add adjustable span between low and high switches. Numerous configurations allow you to open or close contacts on pressure or vacuum increase. Optional enclosures are offered for outdoor applications needing weather resistant construction (PQW) or where hazardous conditions demand the explosion-proof protection provided by the PQE series. The latter is rated for Class I, Groups C and D; Class II, Groups E, F and G.