Residual current circuit breakers (RCCBs) are components for implementing the protective measure 'protection by automatic shutdown of the power supply' in accordance with the requirements of VDE 0100 Part 410 or corresponding international installation regulations. Devices in the DFS 4 series are compact two- or four-pole residual current circuit breakers. In the standard version, they only take up four division units. While the DFS 4 version for alternating and pulsating direct residual currents is designed for three-phase networks, but can also be used in single-phase networks, there are special versions for single- or three-phase operation in the universal current sensitive versions (type B, type B+). Despite the compact dimensions, a large number of different tripping currents and characteristics are available for rated currents - depending on the version - up to 125 A. All devices are available in the 'HD' version, which is particularly suitable for use in harsh environments (tunnels, swimming pools, etc.). They also have large double-deck terminals for accommodating large conductor cross-sections, a practical multi-function switch toggle and can be labelled with pre-made labels using free software. DFS 2 and DFS 4 with the B+ residual current characteristic detect smooth DC residual currents as well as all other type B+ residual currents in accordance with DIN VDE 0664-400. The operating voltage required for this is taken from the mains voltage. Correct voltage supply is guaranteed if the voltage between the mains conductors is ? 50 V. Type A residual currents are detected regardless of the mains voltage. Furthermore, these RCCBs detect residual currents of all frequencies up to 20 kHz with a maximum trigger threshold of 420 mA. Compared to devices with the B SK characteristic, devices with the B+ characteristic therefore offer a higher level of fire protection, i.e. fire protection even with residual currents with frequencies above the rated frequency. Fault protection in accordance with VDE 0100 Part 410 is provided with an appropriate earth resistance over the entire frequency range of residual current detection. The maximum permissible earth resistance is calculated as the quotient of the permissible touch voltage and the highest tripping residual current in the entire detected frequency range. Since the tripping current frequency response of RCCBs of type B+ is significantly below the characteristic curve of an RCCB with SK characteristics for the same rated residual current, their use requires lower leakage currents in the system to be monitored. In addition to the universal current sensitivity of types B or B+, the MI variant is equipped with a tripping threshold of 6 mA for direct residual currents. This prevents pre-magnetization of upstream RCCBs of types A or F, so that they can continue to fulfill their protective function. Devices in standard design are designed for monitoring circuits with a rated voltage of 230 V or 400 V.400 V and a rated frequency of 50 Hz. Properties: - tripping threshold of 6 mA for smooth DC residual currents, - available with rated currents of 16 A to 63 A and a rated residual current of 30 mA, - neutral conductor in standard design on the left, all RCCBs are also available with N conductor on the right at no extra cost, - universally sensitive for residual currents with frequencies and mixed frequencies from 0 Hz (smooth DC) to 20 kHz, - meets the requirements of the construction regulations VDE 0664-10, VDE 0664-400, ÖVE/ÖNORM E 8601, - high immunity to transient leakage and fault currents due to slow response of the tripping, - electromagnetic compatibility in accordance with VDE 0664-30 and VDE 08396-2 (interference immunity for industrial applications), - high availability of the voltage-dependent detection of smooth DC residual currents and AC residual currents with frequencies unequal to 50/60 Hz through full functionality with mains voltages from at least