A computer input device includes a base, a movable member that is displaceable relative to the base, and a sensor that is operably coupled to the movable member. The sensor provides an output signal to circuitry indicative of position of the movable member relative to the base. The circuitry defines...http://www.google.de/patents/US7046229?utm_source=gb-gplus-sharePatent US7046229 - Computer input device providing absolute and relative positional information
