The PetSafe Smart door will slightly raise upward when activated by the collar key, allowing your pet to go through the opening. The door then lowers onto a locking ridge to secure the flap. The collar key (Battery required) is solid, water resistant and and small enough to worn by a small or large dog. This door is a good choice for allowing access to the outside for a dog while keeping a cat indoors.
Electronic Dog Doors, SmartDoor, PetSafe Smart Door - Dog Door Mart
The High Tech Pet is a new dog door manufacturer but their motor-driving and vertically sliding dog door is one of the very rare and unique designs. It's a smart dog door in a way that it can be activated by an ultrasonic dog collar (MS-4) which makes High Tech Pet's product one of the best dog doors and a very convenient option for many pet owners.
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The only drawback of this electronic dog door (and the main complaint of most customers) is that the smart collar for pet doors uses a specific set of batteries that can be bought only from the manufacturer. This is obviously a big issue for most because it adds extra cost; however, another review on Amazon for this dog door has proposed a solution to solve this tricky adjustment from the manufacturer.
Electronic SmartDoor™ by PetSafe - GRP-ESD