The Siemens 3SF7844-8TB04-0SS1 is a Type 4 safety light curtain receiver — the receiving half of a finger-protection guarding pair. Its 14 mm resolution means it catches a finger reaching into the hazard zone (finger-protection class per IEC 61496-1), and the 300 mm protected height covers a typical machine access opening. The 0 to 6 m range gives you flexibility in mounting distance from the emitter. PROFIsafe bus connection ties it directly into a SIMATIC FS420I safety CPU, so no separate safety relay is needed between the curtain and the controller — the safety signal travels over the fieldbus.
Type 4 is the highest safety integrity level for light curtains per IEC 61496 — it's designed for guarding where a failure could cause serious injury. The 14 mm resolution is the critical number: it's the smallest object the curtain can reliably detect. That's finger-protection level, not hand or body. If your application only needs hand detection (30 mm), this part is over-specified and more expensive than a Type 2 or 30 mm Type 4. The 300 mm protected height is the vertical span the receiver covers; match it to the emitter of the same height. The 0 to 6 m range is the maximum separation between emitter and receiver — fine for most machine cells, but confirm your mounting distance falls inside it.
This receiver is part of a safety light curtain system used to guard hazardous machine areas — press brakes, robotic cells, packaging lines, assembly stations. It mounts to the machine frame or guarding structure, aligned optically with the matching emitter. The PROFIsafe connection means it integrates into a Siemens safety PLC network without extra hardware. The receiver itself is the passive side; it communicates the curtain status back to the safety controller.