Amazon.com: Hicello SMC Type DA73 Air Cylinder Magnetic Reed Switch, Proximity Pneumatic Sensor LED Indicator Compatible for CDQ2B/CD85N/CXV/CXT/CDQM/CRA1 : Industrial & Scientific
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SMC Corporation - D-M9N - Solid state sensor, NPN out, direct mount, 4.5 to 28V, Red LED, D-M9 Series - RS