We have a used battery powered pet door that we had purchased for our cat to get in and out of the house and keep other cats and varmits out of the house. It works with your pet who is chipped or you can use a tag on their collar. The unit stores up to 32 different IDs It was easy to install and to program. We purchased it about 2 years ago on amazon and we are selling it as our cat died and we don't plan to have anymore pets.