Sirius Safety Switch Device Basic Unit Standard Series. Relay release circuits: 3 normally open contacts plus relay signaling circuit with 1 normally closed contact. Us = 110 - 240 V AC/DC 50/60 Hz, screw connection. The Sirius 3SK1 safety switch device is designed for standalone safety applications. The Standard 3SK111 basic units are characterized by simple and variable functionality, providing an economical entry into the world of safety switch devices. They are ideally suited for safety functions with only a few sensors and release circuits. These devices have comprehensive global approvals, making them well-suited for international use and export. The devices are available in a 24 V variant or with a wide voltage range, relay or semiconductor outputs, and consistently with screw or spring-loaded connections (Push-In). Extensive accessories such as sealing covers, mounting brackets for wall installation, and coding pins facilitate handling. The 3SK safety switch devices replace the proven 3TK28 series. Safety is a Sirius business.