The Siemens 3SF7844-8BB20-0SS1 is a Type 4 safety light curtain receiver from the SIMATIC FS420I series, with a 14 mm resolution and a 1350 mm protected height. It is designed for finger and hand detection in guarding applications, blanking enabled, with a sensing range of 0 to 6 meters and a PROFIsafe bus connection for direct integration into a safety-rated fieldbus network.
Type 4 per IEC 61496-1/2 means this light curtain is rated for the highest level of safety integrity — capable of detecting a 14 mm object anywhere in the protected field, even with a single component failure. That 14 mm resolution catches fingers reaching into the hazard zone (finger-protection class), so it suits press brakes, assembly stations, and robotic cells where hand access must be prevented without stopping production flow. The 1350 mm height covers a typical standing operator's reach zone. Blanking allows fixed or floating objects (e.g., a workpiece fixture) to pass through the field without tripping the safety output, which avoids nuisance stops on automated lines.
Where this class of part is used
Safety light curtains guard point-of-operation hazards on machinery — presses, cutters, packaging machines, assembly stations — where an operator or robot arm reaches into the danger area. The PROFIsafe bus connection on this receiver means it communicates safety signals directly to a F-CPU (e.g., SIMATIC S7-1200F/1500F) without hardwired safety relays, reducing panel wiring and enabling diagnostics like blanking status and beam degradation. Mounting columns and brackets are typically sourced separately; the receiver aligns optically with the matching transmitter (3SF7844-8BB20-0SS0 or similar FS420I emitter).