There is an instruction video somewhere on how to use it. There is a button you use to set the speed and the angle of rotation. It took me a while to figure it out, even with the video.
Here's the video that shows how the calibration button works with the switch. The first mode sets the angle. The next mode sets the speed. My understanding is that the early kits did not have the button, so he contacted the wires as seen in the video: Arthur Klose