We have focused on video intercom almost 20 year, here is our advantages of 2-wire video intercom:all in one : power, audio,video signals are transmitted by one cable;Flexible cables optional: parallel cable, twisted cable,CAT5/6,UTPCentral power supply, especially no black plug to home socketNo polarity: never afraid of electric shockQuick configuration: Plug-and-Play connectors and DIP switches settings.