Apartment Video Door Phone – is mainly installed where no of flats are many, particularly in a high rise buildings. In such system Video monitors are installed in each flats but only 1 Outdoor station is fixed at the ground floor lobby of the house, generally outside the entrance.
When the visitor comes, he press the desired Flat no (code) in the outdoor station, the person inside the flat see the pictures and talks with visitor. After he is sure to meet the visitor, he opens the Door Lock at the entrance of Lobby. After the visitor reaches the desired flat, there is a 2nd Outdoor station (Optional), the visitor again press the bell and the function is repeated.
Wiring – There are various technologies to connect between Video monitor and Outdoor station.
Wireless – In this system there are no wires between Monitor and outdoor station. The communication is vide 4.33 Ghz Wireless technology. But it is not reliable beyond 20~30 meters.
2 Wire Technology – is also used but not popular.
4 Wire Technology (also called NCX) is most common technology used. The 4 wires are
+12V DC GND Video Audio
Cat 6 – wires are slowly replacing 4 wire technology in the market, where all the Monitor and outdoor stations are connected through Cat 6 wire in TCP/IP network (also called LAN network). In latest Video Intercom System, the TFT monitor are replaced by Touch screen LCD screen and Android operating system is used, so that the system is connected in wifi / internet and can be controlled by cellphone also.