For use with Hammacher Schlemmer's Tested Best Video Monitoring System, additional camera can be wall-mounted or stood upright, and the lens itself adjusts for precise focusing; placed on a shelf near the back door or on the wall beside an entryway, it discreetly looks and listens, broadcasting audio and video to the monitor. Using the same 2.4 GHz technology found in cordless phones, the camera communicates with the receiver (not included) through walls, floors, and ceilings, even when 300 apart. Using infrared technology, the camera can see up to 10 in total darkness without a significant loss of image sharpness; the picture quality of other tested models diminished severely during nighttime use. Plugs into AC, or operates from four AA batteries.