A fully automatic, motor diven door that opens completely under its own power. The door is activated by an ultrasonic pet collar. Features an attractive, translucent Lexan door panel that quickly and quietly powers upward, disappearing into the slim, stylish housing. Has an automatic, dead bolt locking feature that guards against would-be intruders. Only the coded signal from your pet’s collar will open the door.Has a directional sensing system that operats a motor drive, fully autoamtic panel–opening only when your pet is on a direct approach, not just when wandering by or when sitting or sleeping next to the door.Operates on a standard AC wall adapter (included) or optional 12 volt rechargeable battery (sold separately).Manual open/close buttons.Automatic battery power monitoring.Has four access modes: in only, out only, in and out or closed and locked. The dual range controls allow you to adjust separate activation distances for inside and outside your home.Comes with one thin and lightweight battery-powered ultrasonic collar (additional collars sold separately). Each collar uses one type 2430 lithium battery (included). The one size collar fits any size pet from kitten to St. Bernard.Operates on the safe principle of gravity closure with an automatic safety retraction system to provide an extra level of safety by causing the lightweight panel to instantly retract if it encounters 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. An optional wall framing kit is sold separately.Medium model is for pets up to 30 lbs. The door opening is 8 1/4″”W x 10″”H; with the overall size of the unit being 12″”W x 28 5/8″”H.