Your cats microchip is her key to outdoor freedom. The PetSafe Microchip Cat Door reads your cats unique 15-digit microchip ID to let her in and out of the house. This door allows you to program up to 40 pets, so its great for multi-pet households. Since it only reads your best friends microchip ID, you wont have to worry about any unwanted animals wandering into your house. Programming your cats microchip to the door is quick and easy your pet will be heading out to play in no time! If you have a pet in your home without a microchip, programmable collar keys are sold separately. The door has a 4-way lock so you can set it to Locked, Unlocked, Enter Only or Exit Only to keep your cat safe and secure. This battery powered door will signal when its time for you to change the batteries. Please note that this microchip cat flap can read all FDXB microchips. Your cat deserves the best. Trust PetSafe to keep your pet healthy, safe and happy.