Residual current circuit breakers (RCCBs) switch off the power supply when dangerously high residual currents occur. In this way, they protect people, animals and systems. Devices in the DFS 4 series are compact four-pole residual current circuit breakers for single- or three-phase networks. In the standard version, they only take up four division units. The universal current sensitive switches detect smooth DC residual currents as well as all other residual currents in accordance with DIN VDE 0664-400. The PV variant was specially developed for use in photovoltaic systems and offers the highest possible level of protection. With a PV-optimized short-time delay, the universal current sensitive residual current circuit breaker is resistant to surge currents. This means that it offers higher system availability through fewer false trips. 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: All-current sensitive for fault currents with frequencies and mixed frequencies from 0 Hz to 20 kHz, fire protection in accordance with VDE 0100-420, fully functional with mains voltages from at least 50 V AC on any two active conductors, high short-circuit strength, double-sided double-deck terminals for large conductor cross-sections and rail connection, switch position indicator, multi-function switch toggle with three positions: 'on', 'off', 'triggered', neutral conductor position as desired, mounting type: quick attachment to mounting rail, installation position as desired, feed-in preferably from above, areas of application: RCCBs of the PV variant are suitable for private, commercial and industrial installations with TN-S, TT and TN-CS systems in which photovoltaic systems are installed. Notes: suitable for use in 50 Hz alternating current networks, not suitable for use on the output side of controlled electrical equipment such as frequency converters.