US Patent 8094806 Input devices and their use

A touch-sensitive input device has an exposed, continuous surface defining a planar area, and a grid of sense elements coextensive with the area of the exposed surface and responsive to engagement of the exposed surface by an operator to establish a position of said engagement of the exposed surface. The exposed surface varies in elevation across its planar area to form a series of tactile features. The exposed, continuous surface is affixed to the grid of sense elements. An electronic circuit is configured to interpret large-scale capacitance variations of the grid as an intended input from the operator in a region identified by the capacitance variation, and to interpret small-scale capacitance variations of the grid as a position of engagement of the exposed surface by the operator.