The Siemens 3SF7844-8MD26-0SS1 is a Type 4 safety light curtain receiver from the SIMATIC FS420I family, designed for point-of-operation guarding where a 30 mm resolution catches fingers approaching the hazard zone (finger protection per IEC 61496-1/2). The 1800 mm protected height and 0 to 18 m range cover large access openings on assembly lines or robotic cells. Muting function integrated means it can blank out fixed obstructions (like a conveyor pallet) without disabling the safety output. Communication is over PROFIsafe via the bus connection, so it drops directly onto a SIMATIC safety PLC without a separate safety relay or interface module. That saves a DIN-rail slot and cuts wiring time on a panel build.
Type 4 per IEC 61496-1 means the highest level of fault tolerance and self-checking — the curtain detects internal failures within a single scan cycle and goes to the safe-off state. That makes it suitable for safety applications up to SIL 3 / PL e without an external safety monitor. 30 mm resolution means a 30 mm diameter object (roughly a finger) will be detected anywhere in the protected field. For hand-access guarding, that's the standard spec. The 1800 mm height covers a full standing-person opening; the 0-18 m range lets you set the transmitter-receiver distance to fit the machine footprint. Muting is built in, not an add-on module. That means the curtain can ignore a fixed obstruction (like a part on a conveyor) while still guarding the rest of the field. The muting sensors and logic are handled through the PROFIsafe connection, so no extra wiring to a muting module.