Residual current circuit-breakers (RCCBs) are components for implementing protective measure "Automatic switch-off of power supply" as per VDE 0100 part 410 or corresponding international installation regulations. Series DFS 2 devices are compact two-pole residual current circuit-breakers for single-phase networks. In the standard design, they only take up two module width units of space. In spite of the compact dimensions, a number of different tripping currents and characteristics are available at rated currents, depending on the design, up to 125 A. All devices are available in the "HD" design, which is especially suitable for use in extreme environments (tunnels, swimming pools, etc.) They also have large two-tier terminals for large conductor cross-sections, a practical multifunctional switch toggle and can be provided with pre-prepared labels using free-of-charge software. Series DFS 4 devices are compact two or four-pole residual current circuit-breakers. In the standard design, they only take up four module width units of space. While DFS 4 devices are designed for AC and pulsating DC residual currents for three-phase networks but can also be used in single-phase networks, there are also special variants in the AC/DC sensitive designs (type B, type B+) for single or three-phase operation. In spite of the compact dimensions, a number of different tripping currents and characteristics are available at rated currents, depending on the design, up to 125 A. All devices are available in the "HD" design, which is especially suitable for use in extreme environments (tunnels, swimming pools, etc.) They also have large two-tier terminals for large conductor cross-sections, a practical multifunctional switch toggle and can be provided with pre-prepared labels using free-of-charge software.