The PetSafe SmartDoor allows you to control the access of your pets. When the SmartDoor is set to Automatic mode, only your pets wearing the SmartKey can pass through the SmartDoor. As your pet enters the adjustable range of the SmartDoor, the SmartDoor detects the SmartKey and unlocks automatically. The range is adjustable up to 3 feet. After your pet passes through the Smart Door, the door will lock automatically. Without the SmartKey, no other animals can pass through.