The Siemens 3SF7844-8BB04-0SS1 is a Type 4 safety light curtain receiver from the SIMATIC FS420I series, designed for finger-protection applications with a 14 mm resolution. The 300 mm blanking capability lets you define fixed or floating opaque zones through the protected field — useful when a machine fixture or workpiece must pass through the curtain without triggering a stop. The 0 to 6 m operating range covers most single-side guarding layouts on a production line.
Type 4 per IEC 61496-1/2 is the highest safety integrity category for electro-sensitive protective equipment — it can detect a 14 mm object (finger-protection class) and is fail-safe against single faults. The PROFIsafe bus connection integrates directly into a SIMATIC safety controller over the standard PROFINET infrastructure, eliminating the need for a separate safety relay or OSSD-to-PLC interface. Blanking at 300 mm means you can mask a zone up to that width without reducing the safety rating, as long as the blanked area is fixed or floating per the configured logic.
Deployment context
This receiver pairs with a matching Type 4 emitter (same series) and mounts in standard safety-light-curtain columns or machine frames. The PROFIsafe connection uses a standard M12 bus connector, so the cabling follows the same fieldbus topology as the rest of the safety I/O. In a guarding application, the 14 mm resolution means it catches fingers reaching into the hazard zone — suitable for press brakes, assembly stations, and robotic cells where hand access must be prevented without a physical barrier.