The units are rugged, incremental encoders that convert shaft rotation into a current sinking pulse train. Internally, a single L.E.D. light source and a photo logic sensor in conjunction with a shaft-mounted, durable, metal-etched encoder disc, provides signal accuracy and reliability to 10 KHz. The DC input power supply requirement is a versatile +8 to +35 VDC, and is reverse polarity protected. The NPN Open Collector Transistor Output is current limited to 40 mA and is compatible with most RLC counters, rate indicators, controllers and accessories.