The Siemens 3RG7641-3HD00 is a SIMATIC PXO220 M18S retro reflective sensor with polarized optics, straight barrel, M18x65mm housing. It runs on 10-30V DC, outputs NPN light-on at 150mA, and terminates in a 4-pole M12 connector. Rated IP67 for washdown areas.
The 3m sensing range is for a standard reflector; polarized optics reject false triggers from shiny targets. NPN light-on output sinks current to ground when the beam is made — common for Siemens PLC inputs. The 150mA load limit covers most small relays and PLC inputs directly.