An electrical tool that facilitates two-way communication between people is an intercom system. Intercom systems also enable occupants of a building to remotely unlock a gate or door for visitors.
Throughout history, intercom systems have taken on a variety of shapes. People had to speak via metal tubes in the early intercom systems, which carried their sounds like two cans on a string. However, new electronic intercoms are equipped with circuitry that can digitally broadcast and receive voice and video.
Although intercom systems have many uses, their main function is to facilitate communication and access to real estate.