Sirius Safety Switch Device Basic Unit Standard Series. Relay release circuits: 3 normally closed contacts plus relay signaling circuit with 1 normally open contact. Us = 24 V AC/DC. Spring terminal connection (Push-In). Sirius 3SK1 safety switch device for standalone safety applications. The Standard 3SK111 basic units are characterized by simple and versatile 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 terminal 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.