Interfones

Interfones, commonly called intercoms, are electrical communication systems that enable real-time voice communication within a building or campus and often provide access control at entry points. They can be wired or wireless, analog or digital, and may include video capability in addition to audio.

Systems vary by technology and can be wired or wireless, analog or digital, and may include video capability in addition to audio. Configurations range from a single indoor monitor connected to a single outdoor door station to multi-station networks linking multiple indoor units with several door stations. In IP-based implementations, devices may be integrated with a data network and accessed remotely via smartphones or computers.

Core components typically include a door station with microphone and speaker, one or more indoor master or sub stations, and a power supply. Video intercoms add a camera at the door station and a display at the indoor unit. Many systems include a door-release relay for controlled entry. Some configurations use traditional wired circuits, while others use wireless transceivers or network protocols such as SIP.

Primary uses include entry control for residential buildings, offices, hotels, and institutions, as well as internal staff communication. Benefits include improved security, visitor verification, and convenience. Limitations can include installation and maintenance costs, potential security vulnerabilities in networked systems, and privacy considerations in shared spaces.

Intercom concepts date to early 20th-century telephony and electromechanical systems. Early door-telephone systems used wired bells and speaker units. Modern intercoms evolved with advances in audio electronics, then video and networking technologies, leading to current analog, digital, and IP-based systems.