Abstract: A housing is constructed to define individual areas for depression to identify individual indicia such as numbers or the letters of the alphabet. A hard, electrically insulating material is attached to the housing to transmit strains produced in the housing by the depression of the individual areas on the housing. A plurality of thin sheets of an electrically insulating material are provided, each being attached to the insulating material at positions corresponding to the individual areas in the housing. A plurality of thin sheets of an electrically conductive material are also provided, each attached to an associated one of the thin sheets of insulating material. A plurality of ceramic crystals are also included, each attached to an individual one of the electrically conductive sheets. The electrically conductive sheets may be attached to the housing, which is preferably made from an electrically conductive material. This causes one surface of each ceramic crystal to be common to the adjacent area.

Abstract: A housing, preferably electrically conductive, defines individual areas for depression to identify individual indicia, e.g., number, alphabetical letters. A hard, electrically insulating material attached to the housing transmits strains produced by the depression of the individual areas on the housing. A plurality of thin electrically insulating sheets are attached to the hard insulating material at the individual areas in the housing. A plurality of thin electrically conductive sheets attached to the thin insulating sheets. The insulating sheets and the conductive sheets may constitute printed circuit segments. A plurality of ceramic crystals are attached to individual ones of the conductive sheets. The electrically conductive sheets are preferably coupled electrically to the housing. This causes one surface of each crystal to be common to the adjacent area.