Arduino Whole House Telephone Intercom
If you often shout to someone in another room, or your wife has to run to the garage to tell you dinner's ready, this project may be for you. We have used an earlier version of this home telephone intercom system for a few years, built with hard-wired random logic. It is convenient, and uses existing wiring and phones. I decided to rebuild it around an Arduino microprocessor board to improve features and simplify custom circuitry.
Connect this intercom control unit to your premises telephone wiring, and separately to your telephone company service line. Use the intercom's distinctive ring to initiate a local conversation, and then converse between premises phones without interference from the outside telephone line. When the intercom function is not in use, premises phones are connected to the outside line as usual.
The intercom requires household power. If power fails, premises wiring is connected to the outside telephone (Telco) line.
Update! These pages describe a project you can build yourself. A commercial product, ready to install and with improved performance, is now available. For details, see the Update page. See here for a benefit summary.