Residual current circuit breakers (RCCBs) disconnect the power supply when dangerously high fault currents occur, thereby protecting people, animals, and installations. DFS 4 are two- or four-pole residual current circuit breakers for single-phase or three-phase networks. In standard design, the compact devices are four division units wide. They are available with many different types of fault currents and designs with rated currents up to 125 A. The large double-decker terminals can accommodate large conductor cross-sections. The triggered position of the multifunction switch knob facilitates troubleshooting. The free labeling software assists with marking. Type F switches are sensitive to mixed frequencies. They provide protection against pulse and alternating fault currents, as well as fault currents with mixed frequencies deviating from 50 Hz, independent of mains voltage. They are also enhanced to be shock current and lightning resistant. Devices in standard design are suitable for monitoring circuits with a rated voltage of 230 V.