61R128-075 - 

Grayhill 61R Series Optical Encoders, 5 Pin
The 61R series high resolution optical encoders offer either 25, 32, 50, 64, 100, 128 and 256 cycles per revolution positions. They have an extremely rugged construction and options include either pre-wired or with pins and the fifth pin offers a polarized connection. They are extremely cost effective and have an operational expectancy of more than 10,000,000 rotations helping to reduce maintenance.