The Brinno PeepHole Viewer uses an LCD panel to display who is at your door without alerting them to your presence. The PeepHole Viewer turns a hard to see peep hole image into a big bright image. Simply push the button to see a large image of the person outside your door. The image is easy to see for people of any height and is similar to that on the display of a digital camera. The viewer compensates for low-light images and eliminates "fish eye" distortion. A second press of the button provides a zoomed image, which enlarges the center of the image for viewing facial details. Repeated presses toggle between regular and zoom modes. Turns off automatically after 10 seconds to conserve battery life. When the batteries are low, the red Low Battery Light flashes. Replaces existing peep hole in doors 1-3/8" to 2-1/4" thick. Quick, easy installation. Requires 2 AA batteries (included).