The Siemens 3SF7844-8BD13-1SS1 is a Type 4 safety light curtain host receiver from the SIMATIC FS420I series. It provides a 30 mm resolution over a 900 mm protected height, with a sensing range of 0 to 18 m. The PROFIsafe bus connection integrates it directly into a safety-rated PROFINET network, eliminating the need for a separate safety relay or interface module. Blanking capability allows fixed or floating objects within the field to be ignored, so you can pass workpiece carriers or fixtures through the curtain without tripping the safety output.
As a host receiver, this unit pairs with a matching transmitter (same resolution and height) to form a Type 4 safety light curtain per IEC 61496-1/2. The 30 mm resolution provides finger detection — suitable for access guarding where a hand or finger entering the hazard zone must stop the machine. The 900 mm height covers a typical machine-loading aperture; for taller openings, multiple curtains can be cascaded. Blanking is configured via the PROFIsafe parameter assignment in the safety PLC (e.g., SIMATIC S7-1200F or S7-1500F). The 0–18 m range gives flexibility for long-reach applications like gantry cells or automated warehouses.
The PROFIsafe bus connection means this receiver communicates safety signals (OSSD pairs) over a standard PROFINET cable, using the PROFIsafe profile (IEC 61784-3). No hardwired safety relay is needed — the safety PLC evaluates the curtain status and triggers the appropriate stop category. This reduces panel wiring and simplifies diagnostics, as the curtain status is visible in the PLC tag table.