Safety Reversing Sensor, a.k.a. Photo-electric Sensors/Photo Eyes/Light Sensor
Located near bottom of vertical track, infra-red sensors reverse garage door when light beam becomes interrupted. This safety feature prevents the door from closing on vehicles, objects, or persons.
Opens and closes garage door via programmed code.
Garage Door Opener(LiftMaster, Chain Driven), a.k.a 'Motorhead'
Motorized device that opens garage door.
'Chain Driven' - type of opener that uses a chain driven by an electric motor.
Chain attached between opener carriage and opener/motorhead. (See above photo/description)