Wall Mount Transmitter / Keychain Transmitter WM-201 is a handy, useful device to control your swing doors at ease as you wish. Equipped with advanced Rolling code technology you can control the opening or closing of swing doors by activating the Door Opener system with a simple press on button. This wall mounted, unique key-chain transmitter also comes with multi-mode operational facilities like: 1. Toggle Operation: One remote button is programmed to do both the opening and closing of the door. 2. Open / Close Operation: One of your remote buttons can open the door and the other button can close it.