Residual current circuit breakers (RCCBs) switch off the power supply when dangerously high residual currents occur. They thus protect people, animals and systems. DFS 4 are two- or four-pole residual current circuit breakers for single- or three-phase networks. In the standard version, the compact devices are four modules wide. They are available with many different residual current types and versions with rated currents of up to 125 A. The large double-deck terminals can also accommodate large conductor cross-sections. The tripped position of the multi-function switch toggle makes troubleshooting easier. The free label software helps with labeling. Type A switches are sensitive to pulse and alternating current. This function is independent of the mains voltage. Devices in the standard version are designed for monitoring circuits with a rated voltage of 230 V, 400 V and a rated frequency of 50 Hz. Properties: tripping independent of mains and auxiliary voltage, sensitive for alternating and pulsating direct residual currents (type A), small size for all rated currents, high short-circuit strength, double-sided double-deck terminals for large conductor cross-sections and rail connection, switch position indicator, viewing window for labels, multi-function switch toggle with three positions: 'on', 'off', 'tripped', connection C1 neutral conductor position on the left, mounting type: quick fastening on mounting rail, installation position as desired, feed direction as desired, areas of application: power supplies for residential and commercial buildings as well as industrial plants with TN-S, TT and TN-CS networks. In IT networks, residual current circuit breakers from this series can be provided for shutdown in the event of a second fault. Use in TN-C networks and to protect systems in which electronic equipment can cause smooth direct residual currents or residual currents with frequencies other than 50 Hz is excluded. Comprehensive protection is not provided here. For such applications, we recommend our all-current sensitive residual current circuit breakers (type B or B+).