These electric devices are used to automate the opening and closing of the garage door. The first overhead opener was invented in 1926. The modern units are more technologically advanced, but they have the same core design and principle of operation. The power unit houses the motor. It is installed on the ceiling of the garage. A track extends from it. There is a trolley which moves along the track. The trolley is connected to the door via an arm. The trolley is moved along the track by a chain drive, screw drive or belt drive. It moves towards the power unit during opening and towards the door spring during closing.
All garage door openers manufactured at present are wirelessly operated via a remote control. All units manufactured in the United States after the beginning of 1993 are equipped with a safety reversal mechanism. Safety sensors usually come with the opener. Some of the main opener manufacturers at present are LiftMaster, Genie, Chamberlain and Craftsman.