Apartment Building Video Intercom (4-wire) with Eight 7" Color Monitor and Compatible Electronic Lock 7" Color LCD Monitor with Night Vision Outdoor Camera 4-wire Connection to Each Unit (you can use regular Cat.5 cable as extension) Automatically take visitor's photo with date & time stamp Any unit can press monitor button to view outside like surveillance camera Unlock the door from monitor (electric lock/strike and power supply for the lock sold seperately)