DIY Frequently Asked Questions / Garage Door Opener')">
Consists of a motor unit that raises and lowers overhead doors upon command of a control unit.
There are three types of drive mechanisms: bicycle-type chain and sprocket, plastic strip and worm-screw drive.
The control unit may be either key or wireless operated. If key operated, the user must leave the car to unlock the door. Wireless versions may be operated via a transmitter that starts the opener motor.
A safety feature is a device that automatically reverses the descent of the door when it encounters resistance when closing. All residential garage door openers must incorporate an optical sensor that will prevent the door from closing if it senses an obstruction.
Economy models have a 1/4-hp motor and heavy-duty units have a 1/3- or 1/2-hp motor.