Amazon.com: Telemecanique XS518BSDAM12 Optimum Series Inductive Proximity Sensor, Heavy-Duty, Short Metal 18-mm Barrel, Flush Mount, 2-Wire DC Wiring, PNP/NPN Input, NO Output, M12 Micro-Connector : Industrial & Scientific
TRI-TRONICS PZICF4 4-Wire, NPN/PNP Output, Maximum Sensing Range Depends ON The Fiber Optic, F4 Glass FIBEROPTICS Block, 880 NM Invisible Infrared, M8 Connector, Infrared Sensor, 10-24 VDC: Amazon.com: Industrial & Scientific
SENSOPART FT 25-R-PS-M4M IP69K Enclosure Rating, Proximity Sensor, 800 MM MAX Working Distance, PHOTOELECTRIC, Teach-in Adjustment, M8-4 PIN Metal Plug, PNP-Normally Open Output: Amazon.com: Industrial & Scientific