[Anupam Goli]

If you look at the back plate of the gearbox on page 3 here, you can see two holes situated around where the back of the output shaft is. Also on that output shaft, there is a smaller 1/4" hole in the shaft (it may be tapped to 1/4-20, i don't remember). You can use the hole in the shaft to insert an encoder shaft, and use the holes on the gearbox plate to create a custom mount for your encoder. Grayhill encoders are pretty good encoders that are easy to mount and use.