Fully automatic, motor driven door opens completely under itsown power Door is activated by an ultrasonic pet collar Four access modes give you complete control A fully automatic, motor driven door that opens completely underits own power. The door is activated by an ultrasonic pet collar. Features an attractive, translucent Lexan door panel that quicklyand quietly powers upward, disappearing into the slim, stylishhousing. Has an automatic, dead bolt locking feature that guards againstwould-be intruders. Only the coded signal from your pet's collarwill open the door. Has a directional sensing system that operates a motor drive, fully automatic panel-opening only when your pet is on a directapproach, not just when wandering by or when sitting or sleepingnext to the door. Operates on a standard AC wall adapter with a 6 ft cord(included) or optional 12 volt rechargeable battery (soldseparately). Has four access modes: in only, out only, in and out or closedand locked. Manual open/close buttons. Automatic battery power monitoring. The dual range controls allow you to adjust separate activationdistances for inside and outside your home. Comes with one thin and lightweight battery-powered ultrasoniccollar (additional collars sold separately). Each collar uses onetype 2430 lithium battery (included). The one size collar fits anysize pet from kitten to St. Bernard. Operates on the safe principle of gravity closure with anautomatic safety retraction system to provide an extra level ofsafety by causing the lightweight panel to instantly retract if itencounters an obstruction during closure. Door is as easy to install as any conventional pet door. They are flush mounted units that require the same size opening as a regular pet door. A self-framing kit is included for door installations. Medium Dimensions: 12" x 28.5" x 2" High Tech Pet Power Pet; Automatic Door, Size: Medium | PetSmart