In the accompanying diagrams, you'll notice that the line from the sails wraps around a fairlead at the top of the Power Assist Winch. This fairlead isolates the tension of the sheet to an angle relatively perpendicular to the user's input force. With this force isolated in one direction, a minimal input force is needed to pull the bottom of the winch assembly a tenth of a millimeter onto a small waterproof switch embedded in the housing. This switch, in turn, activates the winch.