An intercom (intercommunication device), talkback or doorphone is a stand-alone voice communications system for use within a building or small collection of buildings, functioning independently of the public telephone network (Azori 2016). Intercoms are generally mounted permanently in buildings and vehicles.
Video Door Home
Video door-phone (also known as video door entry or video intercom) is a stand-alone intercom system used to manage calls made at the entrance to a building (residential complex, detached family home, workplace, etc.) with access controlled by audiovisual communication between the inside and outside.
A wireless intercom is a telecommunications device that enables voice communication without the need to run copper wires between intercom stations. A wired intercom system may incorporate wireless elements. There are many types of wireless intercom systems on the market.
EPABX (Electronic Private Automatic Branch Exchange) : A private branch exchange (PBX) is a telephone exchange that serves a particular business or office, as opposed to one that a common carrier or telephone company operates for many businesses or for the general public.