FIGS. 4-1, 4A-1, 3B-1, 4-2, 4A-2, and 3B-2 respectively show details of the arrangement of openings 18, 18A, and 18B on circuit board 7 for the two illustrated variations of the first preferred embodiment of the invention, and in particular the manner in which they are arranged in a matrix of rows and columns to permit display of a wide variety of different designs and messages depending on the po