Sirius Safety Switching Device Basic Unit Advanced Series Relay Release Circuits 3 Normally Open Contacts plus Relay Monitoring Circuit 1 Normally Closed Contact Us = 24 V DC Screw Connection. The Sirius 3SK1 safety switching device is designed for autonomous safety applications. The Advanced 3SK112 basic units offer universal applications thanks to their multifunctionality and flexible expansion options. They create an innovative system landscape that can implement complex safety functions with a variety of sensors and outputs. With device connectors, the number of inputs and safe outputs can be reliably and easily expanded without wiring effort between devices. Drives up to 3 kW can be directly integrated into the 3SK system with the fail-safe motor starters Sirius 3SK11 using device connectors. All components have worldwide approvals, making them well-suited for global use and export. The devices are available with relay or semiconductor outputs, either instantaneous or delayed, each with various time ranges, and consistently with screw or spring-loaded connections. Extensive accessories such as sealing covers, mounting brackets for wall installation, and coding pins facilitate handling. Input and output expansions as well as a separate power supply can be used via device connectors without additional wiring effort. The 3SK safety switching devices replace the proven 3TK28 series. Safety is a Sirius business.