A contact-input circuit for a power system device is described for processing a higher voltage signal from power system equipment or another power system device for use by a lower voltage circuit. The contact-input circuit generally includes a voltage threshold detection device adapted to allow current to flow therefrom when it detects that the higher voltage signal reaches a select threshold. An opto-isolator device, which is coupled to the voltage threshold detection device, provides a voltage signal suitable for use by the lower voltage circuit when the threshold detection device allows the current-flow through the opto-isolator.