An intercom (intercommunication device), sometimes known as a door phone, is a two-way voice communications system for use within apartment buildings, elevators, business offices, and home residences. Intercoms are generally mounted permanently in houses and buildings, with some intercom systems incorporating the control of door/gate latches.
There are simple single house intercoms and intercoms developed for collective apartments. Some intercoms are equipped with a camera allowing us to see the person we talk to. This is an enhanced intercom system usually referred to as a video intercom.