This "second generation" Brinno Digital PeepHole Viewer uses a 3 inch LCD panel and a micro SD slot to display who is at your door and capture the image without alerting them to your presence. The PeepHole Viewer turns a hard-to-see peephole image into a big bright image. Simply push the button to see and record 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. An optional Knocking Sensor accessory snaps into the back of the unit and causes the PeepHole Viewer to record a photo every time someone knocks on your door, regardless of whether you"re at home. An optional Motion Sensor accessory mounts wirelessly outside your door and causes the PeepHole Viewer to record a photo when someone approaches the door, whether you"re at home or away. 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-Inch thick. Quick, easy installation. Requires 2 AA batteries (included). Micro SD card is NOT included in package.