The FS401M-K series is a 1P+N pluggable residual current circuit breaker with overcurrent protection for the SMISSLINE TP system. It protects end-user single-phase circuits against overload and short-circuit currents, as well as the effects of sinusoidal alternating and direct pulsating earth fault currents. It also offers protection against indirect contacts and additional protection against direct contacts. The APR (K type) provides an optimal trade-off between safety and continuity of service, thanks to its resistance to unwanted tripping, offering good protection and isolation of resistive and inductive loads.