The Siemens 3SF7844-8MP51-0SS1 is a Type 4 safety light grid receiver — the sensing half of a safety light curtain pair, built for the SIMATIC FS420I platform. It creates a 400 mm x 800 mm detection field with a range of 6 to 70 m, and it includes muting logic, which lets you temporarily bypass the curtain for material pass-through without tripping the safety circuit. The connection is PROFIsafe over the bus, so it integrates directly into a safety-rated PROFINET network without a separate safety relay or interface module.
Type 4 per IEC 61496-1/2 is the highest integrity level for electro-sensitive protective equipment — it's designed for guarding hazard zones where a failure must not lead to loss of safety function. The 400 mm x 800 mm field covers a typical conveyor infeed or robot cell entry point. The 6 to 70 m range gives you flexibility: 6 m for short-reach guarding on a compact station, 70 m for a long aisle or automated guided vehicle corridor. Muting is built in, so you don't need an external muting module; you wire the muting sensors directly to the receiver and configure the logic in the FS420I controller.