Siemens 3SK1121-1CB42 Industrial Safety Relay

Siemens 3SK1121-1CB42 is a SIRIUS safety relay Basic unit designed for industrial safety circuits, providing a compact, DIN-rail mounted interface between safety devices and machine controls. It offers four normally open contacts: two instantaneous NO outputs and two NO outputs with a time delay, all driven from a 24 V DC coil (Us = 24 V DC) via a screw-terminal connection. The unit supports a time-delay range of 0.5 to 30 seconds and is intended for panel installation where safeguarding devices such as interlocks or emergency-stop circuits must reliably interrupt the actuation path to stop machinery when safety conditions are breached.