Cleveland Controls RSS-495-011 Air Pressure Switch

img{max-width:100%}Cleveland Controls RSS-495-011 Air Pressure Sensing Switch
Series RSS-495-011 Air Sensing Switch Kits contain compact, economical Series RSS-495 switches designed for residential furnace and light commercial aftermarket applications. The RSS-495 switches have an adjustable set point range of 0.20''w.c. to 1.0''wc. (They have been factory set to actuate on a pressure rise of 0.20''w.c.) The field adjustability makes these switches ideal for numerous residential and light commercial HVAC applications. 
GENERAL DESCRIPTION AND OPERATION
The thermoplastic housing contains a diaphragm and snap-acting switch. Barbed sample line connectors on each side of the diaphragm accept flexible tubing. The electrical connection consists of male quick connect terminals. The snap action switch can be actuated by a positive or negative pressure, or by a pressure differential.
http://www.unicontrolinc.com/CC%20PDFs/LTRSS495011-07.pdf