Residual current circuit breakers (RCCB) disconnect the power supply when dangerously high fault currents occur, thereby protecting people, animals, and equipment. 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 fault current types and designs with rated currents up to 125 A. The large double-deck terminals can also accommodate large conductor cross-sections. The tripped position of the multifunction switch knob facilitates troubleshooting. The free labeling software assists with marking. Type A switches are sensitive to pulsating and alternating currents. This function is independent of the mains voltage. Standard devices are designed for monitoring circuits with a rated voltage of 230 V/400 V and a rated frequency of 50 Hz, featuring a hermetically sealed tripping mechanism made of a special alloy.