The title page drawing is not necessarily the first of the numbered drawings. Rather, the drawing selected is that which, in the examiner's opinion, best represents the invention. In this case, Figure 3 was used, showing that an important component of the invention is an electrical circuit.

Patent drawings, in general, are not blueprints or exact schematics of a particular device to be manufactured. Rather they are illustrations of the concepts and principals taught in the patent text, and may include flow charts, block diagrams, tables, graphs, and other visually illustrative material. Describing the invention, the patent text will refer to these drawings, and each element referred to in each drawing will be numbered.