PresAirTrol Tinytrol DPDT miniature Alternate Latching Action air switch TVA211A with 1/2"" Threaded Mount and lock ring nut, and a Center Air Spout. Used on an air actuated spa control systems, controls two devices. Alternate Action is Push and the device remains ON, push again and it will Turn Off. Tinytrol air switches are recommended for air hose runs of less than 20 ft. 3 wire terminal connections on this general hot tub air switch - common (always used), NO normally open (usually used) and NC normally closed (not normally used). Connects with 1/8"" air hose, sold separately.