Fault signal switch 1 NO + 1 NC for miniature circuit breakers 5SL, 5SY, 5SP FI/LS 5SU1, FI 5SV (5SU1 requires handle connector 5ST3805-1) Fault signal switch SENTRON 5ST3 as an additional component for residual current protective devices and miniature circuit breakers.These additional components can be mounted universally. They are easy and convenient to install and connect. Thanks to the standard touch protection, safety during installation is reliably guaranteed.Optimal technology for your safety - only from Siemens.