Digital data links are suitable for remote switch monitoring applications. It provides point-to-point contact closure information over a single fiber optic cable. These are deigned to transmit contact closure data over long distances. The FOT-CC transmitter provides a closed contact signal to the FOR-CC receiver, which activates a single pole double throw relay. It provides ground loop isolation and can be used with 50/125 to 200/230 µm fiber optic cable.