The Ani-Mate company produces electronic pet doors for cats and small dogs. These doors run on a 9 volt battery. The small size has a 5 ½ inch by 5 ½ inch opening and is suitable for average cats. Ani-Mate has a larger 7 inch by 7 ½ inch size for dogs up to 15 lbs and large cats. This larger size is sold in two variations. There is a "Large Cat" size with a smaller lighter collar key and a "Small Dog" size with a larger and heavier key. Key size is the only difference between these two doors. The larger key will open the door from a slightly farther distance.
The Lexan flap seals to the frame with a pile weather
strip, and is held shut with a magnet. In addition to
the electronic lock there is a manual 4 way lock that
can be set for in only, out only, fully locked, or fully open.
These doors are normally used to keep strays out, but can be installed "backwards" so that the door will let only your pets that have collar keys out. When doing this type of installation, it is important to caulk the battery cover to keep water out of the electronics.