Auxiliary switch 1 NO + 1 NC. Small power for miniature circuit breakers 5SL, 5SY, 5SP, built-in switch 5TL1, FI/LS 5SU1, FI 5SV (5SU1 requires handle connector 5ST3805-1) Auxiliary switch SENTRON 5ST3 as an additional component for residual current 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. Optimum technology for your safety - only from Siemens.