Siemens 24 V ac/dc Safety Relay Single Channel with 4 Safety Contacts. Number of Channels: 1. SIL IEC 61508: 3. Range: SIRIUS. Reset Method: Automatic, Monitored. Terminal Type: Screw. Length: 100mm. Series: 3SK1. Width: 22.5mm. Depth: 121.7mm. MPN: 3SK1111-1AB30