4와이어 비디오 도어폰이란?

4 wire video door phone, some people also call it 4 wire VDP, is the most widely used video intercom system all over the word. In this system, outdoor station and indoor monitor connected by 4 wire cable. The 4 wire is Video, Audio, 12V and GND. 

This system is easy to install and it has better resolution than 2 wire system, so that it become very popular.