This third generation Brinno Digital PeepHole Viewer is motion activated and uses a 3 inch LCD panel to display who is at your door without alerting them to your presence. The PeepHole Viewer turns a hard-to-see peephole image into a big bright image. The viewer sits on the inside of the door, using a traditional peephole barrel which provides no indication to those on the outside that they're being photographed. With motion activation, the image is captured and stored on the included 4GB micro SD card whether you're home or not, so you can review who's come to your door with a simple push of the button. Images include a time and date stamp. The displayed 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 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. Viewing angle is 92 degrees (40 degrees in zoom mode). The viewer turns off automatically after 10 seconds to conserve battery life. Battery saving technology allows the PHVMAC12 to last for approximately 9,000 triggers. When the batteries are low, the red light flashes. Replaces existing 12mm peep hole (standard in USA) in doors 1-3/8 to 2 1/4-inches thick. Quick, easy installation. Requires 4 AA batteries (included).