are manufactured by GPI Encoders, and are optical incremental encoders that are intended for light industrial requisitions. They require high resolution in a very small package.
The units have LED illumination for long life with >100,000 hours, and have differential photo-detectors for signal stability. They have a maximum line count on disc of 1024, and have maximum cycles/rev of 16,384. They also have an IP50 degree of protection.