... .5 inch screen Color Hands-Free Digital Wireless Video Door Phone System Primary Function: Home or Office Audio and ... a Picture, Increase Volume, Decrease Volume, View Last Picture, View Next Picture, Signal Bar, Battery Bar - Power Source: Internal Battery ... - approx. 250 meters (ideal conditions) - Onboard Buttons/Indicators - Unlock Door, View Monitor. Talk Button, MIC, LED Indicator, Mini USB Input ...