Residual current circuit breakers (RCCB) switch off the power supply when dangerously high residual currents occur. In this way, they protect people, animals and systems. Devices in the DRCCB 5 series are compact two-pole or four-pole residual current circuit breakers with a self-test function. Type A switches are sensitive to pulse and alternating current. This function is independent of the mains voltage. Self-test (ST) switches regularly and automatically carry out a function test of the residual current circuit breaker. This takes place for the system without interruption and without additional wiring effort, as the required power supply is integrated. Properties: monthly self-test, signaling of the operating status by LEDs, configurable auxiliary contact, type of installation: quick attachment to a mounting rail, installation position as desired, feed from above, areas of application: the devices are used wherever electrical systems must not be switched off or are difficult to access. These can be, for example, IT systems or telecommunications systems, agricultural operations. Small wind turbines or sewage treatment plants. Using an optional Modbus interface module, the switching state of the RCCB can be transmitted for remote monitoring.