Auto-Locking System Collar Sensor: The PetSafe SmartDoor Connected Pet Door Key allows you to add another dog to your app-enabled SmartDoor Connected Pet Door and Microchip Cat Door Smart Pet Access: Collar-activated pet entry with auto-locking system ensures only your pets enter; great for multi-pet homes with up to 5 programmed keys Battery-Powered Convenience: Runs on 4 D-cell batteries (not included), and some models include 1 Pet Door Key with an RFA-67 battery for hands-free, everyday pet access Global Mission, Local Care: With U.S. roots and worldwide reach, PetSafe delivers vet- and trainer-recommended solutions and exceptional customer support to create fields of joy for pets 25 Years of Trust: Since 1998, PetSafe has created safe, innovative, and trusted products that bring joy, enhance pet lives, and support the lifelong bond between pets and their families