Characteristics: One door station can support up to four indoor phones. If needed, it can be extended to two door stations supporting up to four indoor phone Hands-free indoor phone, remote door unlocking Infrared-LED in the door station provides a clear picture even in nighttime Professional CCD or CMOS camera with differnt brands for choose,infrared sets providing high image quality even in the night; Flush-mounted design: displayed with B/W or color;Color TFT screen, 3.5'or 4' size are available 30-second ring tones are available, 20-second surveillance, 120-second intercom 12 kinds chord ringing are optional Heavy duty anti-vandal and water-proof door station Network application is optional; you can connect other door stations When you use this door station in a network system, the intercom between management unit and door station is possible With RF card reader function, you can unlock the door by RF card With image storage function.Max can be exceed to 32 sets.