Abstract: A control apparatus which includes apparatus for storing a first digital code, apparatus for storing a second digital code, and apparatus for comparing the first and second digital codes, the apparatus for comparing including first and second generally dish shaped members that are dimensioned and configured for nesting relationship. In some forms of the invention the dish shaped members are each rotationally symmetrical. The first and second dish shaped members may each include a plurality of steps on the face thereof. At least one of the first and second dish shaped members includes a plurality of steps on the face thereof. The other of said first and second dish shaped members may includes a plurality of steps on the face thereof. The apparatus will often include means for conducting disposed respectively in contact with the conductive generally planar members. Some of the generally planar members may have tab portions for connection thereto.

Abstract: A control apparatus which includes apparatus for storing a first digital code, apparatus for storing a second digital code, and apparatus for comparing the first and second digital codes, the apparatus for comparing including first and second generally dish shaped members that are dimensioned and configured for nesting relationship. In some forms of the invention the dish shaped members are each rotationally symmetrical. The first and second dish shaped members may each include a plurality of steps on the face thereof. At least one of the first and second dish shaped members includes a plurality of steps on the face thereof. The other of said first and second dish shaped members may includes a plurality of steps on the face thereof.