What this kit contains and where it goes
The Siemens 3RK3922-2AC10 is a starter package for the SIRIUS Modular Safety System (MSS) 3RK3 platform. It bundles a central unit MSS Advanced with spring-loaded terminals, the Safety ES V1.0 Premium engineering software, and a USB PC cable — everything needed to begin configuring a safety application on a single DIN-rail assembly.
Rated SIL CL 3 per IEC 61508 and PL e per ISO 13849-1, this central unit meets the highest discrete safety integrity level for a modular controller. That means it can handle safety functions up to Category 4 architecture — think emergency-stop chains, light-curtain monitoring, or two-hand control on a press — without needing a separate safety PLC. The PFHD of 7.0 × 10⁻⁹ 1/h (high demand rate per EN 62061) keeps the probability of dangerous failure well below the threshold for continuous-duty safety loops.
Timing and diagnostics that affect your scan cycle
The dark period of the common drivers is 1 ms at 24 V — that's the gap the MSS inserts between output groups during a test pulse, and it's short enough to avoid nuisance dropouts on most loads. Input delay at the digital inputs can reach 150 ms, and the acquisition time (the window the MSS uses to debounce a signal) maxes out at 60 ms. The internal diagnostics test interval runs up to 1 000 s, meaning the MSS performs a full self-test of its safety logic no less often than every 17 minutes.
Termination is via spring-loaded terminals — no screwdriver torque required, just strip and push. The central unit draws 4.5 W operating power, so thermal load inside a sealed enclosure is modest.