A door phone is an advanced communication and access control system designed to enhance security and convenience in residential, commercial, and industrial properties. It enables occupants inside a building to communicate with visitors at the entrance before granting access. Unlike traditional doorbells, door phones provide two-way audio communication, and in many modern systems, video capabilities that allow users to visually verify visitors. These systems have become increasingly popular in apartments, gated communities, offices, hospitals, educational institutions, and standalone homes due to growing concerns about safety and controlled access.

The basic functionality of a door phone system involves an outdoor unit installed at the entrance and one or more indoor units placed inside the premises. When a visitor presses the call button on the outdoor panel, the indoor unit rings, allowing the occupant to answer and communicate.