Honeywell S688A1007 Sail Switch Simplified installations with multi-speed fans, in- accessible air handlers, fan motors with voltage or phase different from controlled equipment; eliminated wiring to system fan Polyester film sail mounted on a micro switch snap switch Removable spring counterbalances sail to allow mounting in either vertical (up or down) or horizontal air flow Low air velocity switch operation makes at 250 fpm and breaks at 75 fpm