Our LiftMaster 50101 (32NOWB) garage door safety edge exterior air switch with metal case is used on doors to respond to obstructions (people or vehicles) in the path of the door. This is a no-contact exterior air switch for use with a standard 2-wire sensing edge that can cause a door to reverse its downward movement when an obstruction is sensed. Wireless air switches like the LiftMaster 50101 from Garage Door Supply Co. can also stop a garage door or gate from being used if the sensor is not working.Product Highlights: