The Passport Pet Access Smart System‚ uses advanced entry and exit technology to provide freedom and peace of mind like no other pet door. Using radio-frequency identification (RFID) technology, the Passport reads the Passport Key‚ worn on your pet's collar. This allows only pets with programmed IDs to enter and exit the home, while keeping out other pets, wild animals, and strays. Choose from advanced selective entry and exit by pet, multiple access options (such as in-only access and out-only access), and access only at specific times of the day. Programming is easy using the LCD screen and 5-button navigation or by connecting to your computer with the included USB cable. A wireless connection allows for convenient future remote programming from any smart device, even when you're not at home. The Passport gives you complete control of each pet‚Äôs access. Fits dogs up to 23 kg in weight and can program for up to 20 pets. Includes one Passport Key, others sold separately.