{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3SK1121-2CB42","brand":"Siemens","brandSlug":"siemens","productSlug":"3SK1121-2CB42","canonicalUrl":"https://aoctrl.com/siemens/3SK1121-2CB42","factsUrl":"https://aoctrl.com/api/mcp/products/3SK1121-2CB42","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SIRIUS 3SK1121-2CB42 safety relay, 24 V DC, SIL 3 / PL e, 22.5 mm width, screw and snap-on mounting.","salesMarkdown":"## Safety relay for guarding circuits The Siemens 3SK1121-2CB42 is a SIRIUS safety relay for enabling circuits, with a Safe Failure Fraction of 99%. The 22.5 mm wide housing mounts via screw or snap-on on a DIN rail, fitting into standard control panels with a depth of 121.6 mm and height of 100 mm. ## SIL 3 / PL e — what it means for guarding SIL 3 (IEC 61508) and PL e (ISO 13849-1) are the highest single-device safety integrity levels, meaning this relay is suited for guarding hazardous machinery where a failure could cause serious injury — e.g., press brakes, robotic cells, or conveyor interlocks. The 99% Safe Failure Fraction (SFF) indicates that 99% of dangerous failures are detected by the internal diagnostics, which drives the high SIL claim without requiring a redundant channel in many architectures. It includes start input, feedback input, and cascading capability, so it can be wired into multi-zone safety circuits or reset loops typical in Category 3/4 structures. Rated for operation from -25°C to +60°C, storage from -40°C to +80°C, with shock resistance of 10g / 11 ms and overvoltage category III / pollution degree 3 — suitable for industrial control cabinets without climate control. EMC emission meets IEC 60947-5-1 Class A, so it is intended for industrial environments; verify compatibility in residential or light-commercial panels. Maximum switching frequency of 360 operations per hour and a minimum sensor input pulse of 75 ms define the safe response timing for monitoring guard-door switches or light curtains.","metaTitle":"Siemens 3SK1121-2CB42 SIRIUS Safety Relay, SIL 3 / PL e","metaDescription":"Siemens 3SK1121-2CB42 SIRIUS safety relay, SIL 3 / PL e, 24 V DC, 3 A switching current, 22.5 mm wide, screw/snap-on mount. Quoted to order against RFQ.","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Safety Relays"],"specifications":{"Depth":"121.6 mm","Solid":"1x (20 ... 16), 2x (20 ... 16)","Width":"22.5 mm","at DC":"0.8 ... 1.2","Height":"100 mm","Maximum":"40 ms","Typical":"30 ms","at 24 V":"3 A","Stranded":"1x (20 ... 16), 2x (20 ... 16)","at 115 V":"3 A","at 230 V":"3 A","Rated Value":"24 V","Start Input":"Yes","Safety Switch":"Yes","at DC maximum":"110 ms","During Storage":"-40 ... +80 °C","Feedback Input":"Yes","lifecycle_stage":"current","During Operation":"-25 ... +60 °C","Fastening Method":"screw and snap-on mounting","Product Category":"Safety relays","Shock Resistance":"10g / 11 ms","Mounting Position":"any","Product Brand Name":"SIRIUS","Degree Of Pollution":"3","Product Designation":"safety relays","Overvoltage Category":"3","Design Of The Product":"Relay enabling circuits","Total Current Maximum":"12 A","according to IEC 61508":"3","according to IEC 62061":"3","power loss [W] maximum":"2.5 W","Design Of The Cascading":"yes","Safety-Related Circuits":"Yes","EMC emitted interference":"IEC 60947-5-1, Class A","With Core End Processing":"1x (0.5 ... 1.0 mm²), 2x (0.5 ... 1.0 mm²)","according to ISO 13849-1":"e","Of The Sensor Input Minimum":"75 ms","Operating Frequency Maximum":"360 1/h","Safe failure fraction (SFF)":"99 %","Without Core End Processing":"1x (0.5 ... 1.5 mm²), 2x (0.5 ... 1.5 mm²)","Type Of Electrical Connection":"spring-loaded terminal (push-in)","Insulation Voltage Rated Value":"300 V","Monitoring Of Floating Sensors":"Yes","Product Function Parameterizable":"sensor floating / sensor non-floating, monitored start-up / automatic start, 1-channel / 2-channel sensor connection, cross-circuit detection, startup testing, antivalent sensors, 2-hand switches, time delay","Safety-Related Delayed Switching":"2","Monitoring Of Non-Floating Sensors":"Yes","Relative Humidity During Operation":"10 ... 95 %","air pressure according to SN 31205":"90 ... 106 kPa","of the ON pushbutton input minimum":"0.15 s","Product Feature Cross-Circuit-Proof":"Yes","operational current at 17 V minimum":"5 mA","Cascading Input/Functional Switching":"Yes","Safety-Related Instantaneous Contact":"2","Surge Voltage Resistance Rated Value":"4 000 V","category according to EN ISO 13849-1":"4","protection class IP of the enclosure":"IP20","stop category according to EN 60204-1":"0 / 1","installation environment regarding EMC":"This product is suitable for Class A environments only. In household environments, this device can cause unwanted radio interference. The user is required to implement appropriate measures in this case.","Magnetically Operated Switch Monitoring":"Yes","reference code according to IEC 81346-2":"F","Recovery Time After Power Failure Typical":"6.5 s","Suitability For Interaction Press Control":"Yes","Touch Protection Against Electrical Shock":"finger-safe","safety device type according to IEC 61508-2":"Type B","Type Of Electrical Connection Plug-In Socket":"No","Type Of Voltage Of The Control Supply Voltage":"DC","Number Of Sensor Inputs 1-Channel Or 2-Channel":"1","Required Spacing For Grounded Parts At The Side":"5 mm","Type Of The Safety-Related Wiring Of The Inputs":"single-channel and two-channel","hardware fault tolerance according to IEC 61508":"1","vibration resistance according to IEC 60068-2-6":"5 ... 500 Hz: 0.75 mm","PFHD with high demand rate according to EN 62061":"3.7E-9 1/h","suitability for operation device connector 3ZY12":"Yes","Mechanical Service Life (Operating Cycles) Typical":"10 000 000","PFDavg with low demand rate according to IEC 61508":"7E-6","for delayed release circuit according to IEC 61508":"SIL3","Installation Altitude At Height Above Sea Level Maximum":"4 000 m; Derating, see Product Notification 109792701","Recovery Time After Opening Of The Safety Circuits Typical":"30 ms","Thermal Current Of The Switching Element With Contacts Maximum":"5 A","adjustable OFF-delay time after opening of the safety circuits":"0.5 ... 30","Backslide Delay Time After Opening Of The Safety Circuits Typical":"40 ms","design of the fuse link for short-circuit protection of the NO contacts of the relay outputs required":"gL/gG: 6A or circuit breaker type A: 3A or circuit breaker type B: 2A or circuit breaker type C: 1A"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":null,"priceTiers":null},"links":{"datasheetUrl":null,"sourceUrl":null,"alternativesUrl":"https://aoctrl.com/api/mcp/products/3SK1121-2CB42/alternatives.json"},"ai":{"faq":[{"question":"What is the depth of 3SK1121-2CB42?","answer":"The depth is 121.6 mm, with a width of 22.5 mm and height of 100 mm, fitting standard DIN-rail enclosures."},{"question":"What wire sizes does 3SK1121-2CB42 accept?","answer":"Solid wire: 1x (20…16 AWG) or 2x (20…16 AWG); stranded wire: 1x (20…16 AWG) or 2x (20…16 AWG); with ferrule: 1x (0.5…1.0 mm²) or 2x (0.5…1.0 mm²)."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3SK1121-2CB42","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/3SK1121-2CB42 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-09-02T08:15:54.622Z","lastPublished":"2026-09-02T08:15:54.622Z","indexable":true}}