The Siemens 3SF7844-8BD08-0SS1 is a Type 4 safety light curtain receiver in the SIMATIC FS420I family, with 30 mm resolution, 600 mm protected height, and a sensing range of 0 to 18 m. It connects via PROFIsafe bus, integrating directly into a safety-rated fieldbus architecture.
Type 4 per IEC 61496-1/2 means this receiver is rated for the highest safety integrity — capable of detecting a 30 mm object (finger protection) across the full 600 mm height. The 0 to 18 m range covers most machine guarding zones from small assembly cells to large robotic workcells. The PROFIsafe bus connection eliminates hardwired safety relay logic; the receiver communicates safety status directly to a F-CPU over the PROFINET network. The 30 mm resolution is the key selection parameter: it catches fingers reaching into the hazard zone, meeting the finger-protection class per IEC 61496-1. For hand or palm detection (40 mm or coarser), a different model in the FS420I family would apply.
Deployment context
Mounts to standard machine guarding frames or T-slot profiles. The PROFIsafe bus connection means the receiver pairs with a Siemens F-CPU (e.g., ET 200SP F or S7-1500F) over PROFINET — no separate safety relay needed. The 600 mm height suits guarding of a typical conveyor infeed or robot cell access point.