Using radio frequency identification (RFID) technology, the Passport Pet Access Smart System reads the Passport Key worn on your pets collar. When your pet approaches the Passport, the system reads the unique ID of your pets Passport Key and if that number is programmed, the pet door will unlock allowing your pet to enter or exit. If a pet or animal is not programmed to the system, the pet door will remain locked. This allows access to only your programmed pet(s) while helping keep out other pets, wild animals, pests and strays. Offering advanced selective entry and exit by pet, multiple access options (such as in-only access and out-only access) and the option to only allow access at specific times of day, the Passport gives you complete control of each pets access. You can set access by pet or easily set the same access setting for all pets with the Master Access option. Pet Tracking shows your pets current location and the last 4 times your pet used the pet door, allowing you to monitor your pets access. Programming is easy using the LCD screen and 5-Star Navigation or by connecting to your computer with included USB cable. A wireless connection allows for remote programming from any smart device, providing ultimate convenience for todays busy pet owners (requires Passport Wireless Card, sold separately). The Passport is programmable for up to 20 pets..