Modern garage door openers transmit a radio signal that has a binary number encoded in it. The transmitter transmits a binary number, the receiver looks for that number, and it only opens the door if it hears the correct number. A great benefit of having this system in your garage door opener is that you do not have to leave your car to open or close the garage door. This feature is greatly appreciated by homeowners who would otherwise have to yank a garage door open and close it again in the rain or bad weather.