2 wire video door phone systemthis complete video door phone system allows you to view and talk to visitors before opening the door there is also an additional function to allow the opening of an electronic lock great for extra security and ideal for use in an apartment or for the elderly and less mobile easy to install night vision to see people in the dark via the 6 infrared leds adjustable volume contrast brightness 15m of cable included function for electronic unlocking ip44 waterproof