Intercom systems — how do they work?

Kim Lange
2 min readFeb 8, 2017
Intercom systems in various styles and designs

An intercom (intercommunication device), talkback or door phone is a stand-alone voice communications system for use within a building or small collection of buildings. Its a two-way communication electronic device that contains circuitry for the purpose of transmitting and receiving audio and/or video transmissions.

Intercom allows a person speaking into a microphone to be heard on a speaker by people in a different room or area.

Intercom solutions have long outgrown the image of the single-line, single-button door buzzer panel. In a wide range of communication and building management settings, intercom is emerging as the future central hub technology that brings together audio and video communication.

Intercoms come in a variety of styles. Some are extremely easy to use while others can be very complicated. There are audio intercoms, video intercoms, integratable and multi-tenant intercoms.

Intercom devices are available in various styles and designs. Some of the designs are simple while others are not. Leaving aside the various designs features, there are intercom devices specially designed for specific functionalities.

Different types of intercom security systems:

Wireless Intercoms
In applications where wires cannot be run, a wireless system is used.

Wired Intercom Systems
A wired system can give you a little more privacy and eliminate possible interference from neighboring systems.

Video Intercom
Typically includes a unit that has a camera, speaker, and a push button going to an entrance door, and an internal monitor unit that can communicate with the entrance unit.

Apartment Intercoms
A visitor presses the correct button for the apartment they want to speak to, and the tenant can speak back and then press a button to unlock the door.

Two-Way Radios
There are two-way radios that communicate with base station intercoms. So you can have the flexibility of a mobile radio that communicates over long distances mixed with the capability a fixed intercom gives you.

Security intercom systems
Security intercom systems are used to provide voice communications between two or more locations for security purposes. Security intercom systems are frequently used between a locked building entrance door and a constantly attended location in the building.

A simple security intercom system consists of one “Master Station” and one “Sub-Station”. The Master Station is typically located at the point inside the building where communications is to be received. The Sub-Station is typically located at the point where the communication is to be originated.



Kim Lange

Consultant in a larger firm. I am a dedicated golfer :) and a father of two lovely children. When the weather permits, i do a little windsurfing too.