Auxiliary switch 1 changeover contact for LS switch 5SL, 5SY, 5SP Built-in switch 5TL1 FI/LS 5SU1, FI 5SV Auxiliary switch SENTRON 5ST3 as an additional component for residual current protective devices and circuit breakers. These additional components can be mounted universally. They can be installed and connected easily and conveniently. Thanks to the standard touch protection, safety during installation is reliably guaranteed. Optimum technology for your safety - only from Siemens.