Our state of the art motor Model D20.

Works like a fishing reel.  Has a reversible motor with open and closed stop settings.  Motor stops door at positions you set.  No counter-weight needed.  Motor can lift-lower a door up to 5 pounds, with a door opening up to 25 inches.  Motor lifts and lowers door smoothly in a few seconds.  It never allows door to drop suddenly. The motor is 120volts 60herts 19watts. Our motors include a one year warranty.