Siemens SIRIUS 3SK1 Equipment Manual page 223

* If there is a common reference potential for the two inputs, it suffices to establish a ground connec‐
tion.
If there are separate potentials or controls, both connections must be assigned.
SIRIUS 3SK1 Safety Relays and 3RQ1 Positively-Driven Coupling Relays
Equipment Manual, 05/2021, A5E02526190021A/RS-AE/005
14.4 Typical circuits of 3SK1 safety relays with 3RM1 Failsafe motor starters
Circuit diagrams
223