What it is and what it guards
The Siemens 3SF7844-8TB13-0SS1 is a Type 4 safety light curtain receiver — the sensing half of a pair that creates a vertical or horizontal protective field. With 14 mm resolution and a 900 mm protected height, it catches fingers reaching into the hazard zone (finger-protection class per IEC 61496-1). The operating range spans 0 to 6 m, so it fits guarding applications from compact assembly stations to wider robot cells.
Integration and bus connection
This receiver connects via PROFIsafe bus to a SIMATIC FS420I safety controller — no separate safety relay needed for the logic. Cycle control is built in, meaning the light curtain handles its own test pulses and reports status over the bus. Mounting hardware and alignment brackets are standard for the FS420I family; the 900 mm column fits typical machine guarding frames.