In accordance with the present invention, an imaging apparatus is provided for forming images on an electrically conductive printing plate. The imaging apparatus has a mounting surface having at least three electrically isolated conductors arranged so that when the electrically conductive printing plate is in registration on the mounting surface, the electrically conductive printing plate defines an electrical connection between all of the electrical conductors; and, an electrical circuit adapted to sense an electrical connection between all of the conductors and to thereupon generate an output signal. In accordance with another embodiment of the present invention, a mounting surface for receiving electrically conductive printing plates is provided. The mounting surface has at least three electrically isolated conductors arranged so that when the electrically conductive printing plate is in registration on the mounting surface the electrically conductive printing plate defines an electrical connection between all of the electrical conductors and an electrical circuit adapted to sense an electrical connection between all of the conductors and to thereupon generate an output signal.