FI residual current circuit breaker, 4-pole, Type B, selective, In: 80 A, 500 mA, Un AC: 400 V. The residual current circuit breaker is the protective device for touch protection. Siemens' patented residual current protective devices are an essential component of the SENTRON protection devices for electrical installations, as they prevent life-threatening electrical accidents by safely disconnecting dangerous fault currents to ground. Electrically ignited fires can be prevented at their inception. Whether through direct contact with parts that are live during operation or through indirect contact with operating equipment, protection is primarily achieved through rapid disconnection. The residual current circuit breakers are characterized by: 1. Comprehensive protection for persons and property against electric shock 2. Whether sinusoidal alternating fault currents or smooth direct fault currents - Siemens offers the suitable type for all requirements as well as special versions. 3. Compliance with standards.