1, Outdoor Unit: Support to open door with RFID cards. With three call button, each button can control a monitor independently. Two way audio between camera and monitors. But the monitors cannot communicate with each other. 2, Indoor Unit: 7” LCD colorful LCD screen, with 25 chord ringtones, one key unlock function, with mute mode. 3, Night Vision: IR night vision, providing clear vision of visitors even in the darkness of night. 4, Function: Support two-way audio and ringback function; Support hands-free intercom and monitoring; Support to adjust the volume of the ring. 5, Applications: Wired connection stability clear vision for home security, can be used for multi apartments, especially suitable for low-rise buildings, don't need to connect to internet!