Fader has two outlets on bottom of unit, you plug your sets of lights into these outlets. With the dial on the face of the unit you control the speed of the fade. as one strings fades out the other string fades in. Super simple to use!
This unit handles 275 watts per channel, that is approx. 55 C7 bulbs, 39 C9 bulbs, 450 Mini light bulbs. These units do not fade LED sets unless the sets/bulbs are dimmable.
Here's a quick sample video of a similar fader.