The PetSafe Electronic Smart Door comes standard with one SmartKey but can be expanded to allow you to control the access of up to 5 pets (with purchase of additional SmartKeys). Only pets wearing the SmartKey can pass through a PetSafe SmartDoor.
These doors use radio frequency technology to operate. Pets wear a collar key that triggers the door to unlock to allow them to go in or out. After your pet passes through it automatically re-locks.