Abstract: An automatic radio actuated mechanism for opening and closing panels, such as a garage door, makes use of an electric motor to rotate a specially constructed spiral drive screw and move a traveler along a track, the traveler being connected to the door to pull the door open or push the door shut. Included in the mechanism is a camming arrangement for precisely adjusting the full open and full closed positions by action of an electronic circuit which activates the motor. For reversing the operating direction of door movement in the event such movement should be obstructed, the motor housing is mounted in a manner allowing it when restrained to swing for a limited distance, one way or the other, thereby to actuate a switch in the electronic circuit for reversing movement of the door.