Sirius safety switching device output expansion 4RO with relay release circuits, 4 normally closed contacts plus relay signaling circuit with 1 normally open contact, Us = 24 V AC, screw connection. The output expansions 3SK serve to supplement a basic device with additional safe outputs with a switching capacity of up to 10 A. They can be connected to any 3SK basic device through wiring. All devices with a control supply voltage of DC 24 V can also be connected to the Advanced 3SK1 and 3SK2 basic devices using the device connector 3ZY12. The devices have four (AC-15 5 A) or three (AC-15 10 A) safe outputs. There is a choice between a control voltage of 24 V or wide voltage. Available with screw or spring-loaded connection (Push-In). The safety switching devices 3SK replace the proven series 3TK28. Safety is a Sirius business.