The speed is controlled by a potentiometer or connected to the breakout board, I think it has just 2 wires going to the spindle, But I have no seen it yet so could be wrong. The seller says that there are power from 230v to power unit then wire to the spindle and the 2 wires from the breakout board. Then 3 wires to the potentiometer from the power supply.
I will know better when it arrives.