By adding a single lightweight unit to your keychain, you'll have easy access to your garage, and you'll even be able to turn on a light before you enter your home! The two-button Keychain Transmitter sends a wireless signal to the Garage Door Receiver (sold separately), which triggers your automatic garage door system to open or close. With the second button, the Keychain Transmitter will turn on a light, fan or appliance that's plugged into a Switch Receiver (sold separately). Programming the Keychain Transmitter is simple; just align the codes to match those on the receiver modules. A battery is pre-installed, so you're ready to use this handy device as soon as the receivers are plugged in. The Keychain Transmitter and Garage Door Receiver are also available to be purchased as a set. For a more permanent access transmitter, the Keyless Entry Transmitter (sold separately) is easily mounted on the wall of your garage for PIN access at any time.