This speed controller is specifically designed for use with our Quiet Cut, DC spindles. It will not work with the AC powered routers or rotary tools. The speed can be controlled with a potentiometer or an external PWMsource such as Mach3. We recommend 48VDC input for best performance with our Quiet Cut DC spindles.
These come with potentiometer on an approximately 1ft (300mm) cable with a knob.
See this blog post explaining how to use it with a gShield and grbl.
If you intend to use this on your X-Carve with the X-Controller you will need to get a separate 48V power supply