The Electronic SmartDoor™ Pet Door gives your pet a key to the house so he can come and go as he pleases. Using radio-frequency technology, the pet door reads the unique signal of a SmartKey™ worn on your pet's collar and triggers the battery power-driven flap to unlock. When the pet door no longer senses your pet's SmartKey™ Collar Key, the flap automatically locks back into place. The SmartDoor™ can detect up to 5 programmed SmartKey™ Collar Keys and also operates in 2 other modes, fully locked mode and unlocked mode. Locked mode does not allow entry or exit for any pet and unlocked mode allows entry and exit for all pets.