Slim DIN Rail Mount NPN to PNP/PNP to NPN Sensor Logic Signal Converter Module: Amazon.com: Industrial & Scientific
Signal Converter, NPN PNP Signal Converter, MRI-24TR/INV PLC Sensor Polar IO Level Conversion Module: Amazon.com: Industrial & Scientific
Amazon.com: Mini LCD Digital Counter Module DC/AC5V~24V Electronic Totalizer with NPN and PNP Signal Interface 1~999999 Times Counting Range : Tools & Home Improvement