fitting round slots (slot 1,slot2)together.
when you turn on the power firstly.The speed cycles low to high .Please press the switch 2 seconds
when you need to stop the device.The flicker frequency of light faster, the speed is higher.
Turning it clockwise, length of it will be longer.Turning it counter clockwise, length of it will be shorter.
caused by many factors such as brightness of your monitor and light brightness.