Sirius Safety Relay Output Expansion 3RO Power, with relay release circuits, 3 normally closed contacts plus relay signaling circuit 1 normally open contact, Us = 115 V AC screw connection. The Sirius 3SK output expansion is designed to complement 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 feature 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 either screw or spring-loaded (Push-In) connections. The 3SK safety relays replace the proven 3TK28 series. Safety is a Sirius business.