The Siemens 3SF7844-8BD04-0SS1 is a Type 4 safety light curtain receiver from the SIMATIC FS420I series, specified with 30 mm resolution and a 300 mm protective height. The 0 to 18 m operating range covers long-reach guarding zones on conveyor lines or gantry cells. Profisafe bus connection integrates directly into a safety-rated PROFINET network, eliminating the need for a separate safety relay or interface module — the receiver talks to the F-CPU over the bus, and the safety function lives in the controller logic.
30 mm resolution means the curtain detects a 30 mm diameter object anywhere in the field — finger-protection class per IEC 61496-1/2, suitable for hand-entry hazard zones. The 300 mm protective height defines the guarded area; pair it with a matching 300 mm transmitter (same series) to cover the full opening. The 0 to 18 m range gives flexibility for long aisles or wide machine perimeters without adding a second curtain pair. Blanking capability (noted in the description) allows fixed or floating blanking of up to two beams, so the curtain can ignore a stationary fixture or a workpiece that must pass through the field. This is configured via the Profisafe bus — no physical bypass switch, which keeps the safety integrity intact.
Integration and deployment
Mounts in standard slotted aluminum guardrail profiles or directly to machine framing via the supplied brackets. The Profisafe bus connection uses a standard M12 connector; cable runs to the next FS420I node or to a PROFINET switch. The receiver draws its power from the bus — no separate 24 V supply needed at the curtain. Alignment aids (visible LED indicators on the housing) speed the optical setup during commissioning.