The Siemens 3SF7844-8MD11-0SS1 is a Type 4 safety light curtain receiver from the SIMATIC FS420I family, designed for guarding hazardous machine zones with a 30 mm resolution and a 750 mm protective height.
The 30 mm resolution means the curtain detects a 30 mm diameter object — finger-protection class per IEC 61496-1 — so it's suitable for guarding access to areas where an operator's fingers could reach the hazard. The 750 mm protective height sets the vertical coverage; pair it with the matching emitter of the same height for a complete light curtain pair. The 0 to 18 m operating range allows the emitter and receiver to be spaced up to 18 m apart, covering wide guarding openings or long conveyor access points. Muting capability means the curtain can temporarily suppress its safety output when a workpiece enters the guarded zone on a conveyor, without stopping the machine — a common requirement in material-handling and assembly lines. The PROFIsafe bus connection integrates the receiver directly into a Siemens safety PLC (e.g., S7-1200F or S7-1500F) over the PROFINET network, eliminating a separate safety relay module and simplifying the wiring and diagnostics.