5SU1 RCBOs in 2-, 3-, and 4-pole versions combine residual current circuit breakers and miniature circuit breakers in one device. They protect people from fault currents and systems from short circuits and overloads. They ensure all-pole protection of final circuits with 2, 3 or 4 outer conductors as well as protection of the N conductor against overload due to harmonics in non-linear consumers such as PC power supplies, energy-saving lamps or consumer electronics.