Safety light grid transmitter — Type 4, 400 x 800 mm
The Siemens 3SF7844-6SP51-0SS0 is a Type 4 safety light grid transmitter from the SIMATIC FS420I series, with a 400 x 800 mm detection zone and a range of 6 to 70 m. It communicates over ASISAFE and PROFIsafe protocols and has no integral output — it is the transmit half of a safety light curtain pair, designed to guard hazardous machine zones where a Type 4 (highest integrity per IEC 61496-1) response is required.
What the Type 4 rating means for fit
Type 4 per IEC 61496-1 means this light grid is rated for the highest safety integrity — it can detect a 14 mm object (finger-protection class) and is designed for applications up to SIL 3 / PL e. The 400 x 800 mm detection zone covers a typical machine access opening; the 6 to 70 m range gives flexibility for longer guarding distances. As a transmitter-only unit, it must be paired with a matching receiver (same series) and a safety-rated controller that can evaluate the ASISAFE or PROFIsafe signal.