Systems and methods for determining the positions of the discs of a mechanical display by using the shadow cast on an optical array by a profiled cam arrangement. The slider according to the present invention has teeth 13 of a comb shaped like a narrow sheet being rectangular in cross section and making a contact at a tip of the teeth with a surface to be slid on. Specifically, a first semiconductor region forms a ground-potential-based circuit, and a high voltage junction terminating structure around a second semiconductor region forms a floating-potential-based circuit.