Add an additional pet to your Electronic SmartDoor™ Pet Door or replace your current SmartKey™ Collar Key. Our innovative Smart Door™ Pet Door recognises the SmartKey™ Collar Key worn on your pet’s collar and unlocks the pet door. After your pet has passed through and the pet door no longer senses your pet's SmartKey™ Collar Key, the pet door automatically locks back into place. Up to 5 SmartKeys™. Collar Keys can be programmed.