Siemens 3SK1112-1BB40 SIRIUS 3SK1 Standard basic units. Siemens 3SK1112-1BB40 is the exact printed commercial reference for a safety relay in the SIRIUS 3SK Safety Relays range. Siemens' official product description is: SIRIUS safety relay Basic unit Standard series electronic enabling circuits 2 enabling circuits plus 1 signaling circuit Us = 24 V DC screw terminal.