Edwin Thorne III, Mark T Hanson, John P Pennock, Luis A Reyes: Method and apparatus for generating directional and force vector in an input device. Microsoft Corporation, Seed and Berry, September 23, 1997: US05670955 (42 worldwide citation)

A thumbpad input device that enables a user to generate direction and speed by manipulating a round elastic pad. The underside of the pad is lined with a set of uniformly spaced contacts positioned in a circular pattern. Each contact is paired with a corresponding switch that is coupled to a circuit ...