Siemens Configurable 24 V 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. Depth: 121.7mm. Configurable: Yes. Width: 22.5mm. Series: 3SK1. MPN: 3SK1121-1AB40