Audio and video intercom
Audio intercom - this is a basic protection system of office buildings, residential buildings or apartment buildings entrance control. Audio intercoms can provide duplex or semi-duplex communication, convenient communication with outside areas or among staff members working in different offices, as well as anti-theft applications. Access is only allowed through the entrance door, which is controlled by a person from inside the building.
Video intercom - In the case of video intercoms, which are mostly used in residential buildings, people from inside the building can actually see the person who is at the entrance door. Video intercom are black & white or coloured, and can have several functions, depending on the model.