Whole House Telephone Intercom

This project will enable all your household telephones to do double duty as a handy intercom system.

I would tell you where to find out more about it, but an error when I post says I cannot include links.

You will be able to post links in your second post–it’s an anti-spam measure.


OK, thanks. Let's try this. Here's a picture:

DIY project details at Arduino Whole House Telephone Intercom

I am updating this design with several improvements:

  • Circuit on 3.5 inch square PCB
  • More robust phone ringing signal - drives about 10 ringer equivalents
  • Reduced power dissipation, no heat sink required
  • Lower cost and size - separate isolation transformer eliminated
    New circuitry works well on a breadboard. Here's a CAD rendering of the proposed PCB:

The green lump to the right represents screw terminals to attach Telco and Local phone lines. 48 Volts from an isolated "wall wart" switching type supply enters via the 2.1 mm jack at lower left. Mount this board in a convenient enclosure, such as a 4 inch junction box, hook up power and phone lines, and you're done.

This is no longer strictly Arduino, since the processor is embedded directly in the circuitry.

Does anyone have a recommendation where to get PCBs fabricated?

Nice project.

I have never used them but sparkfun linked to batchpcb.com in this project post.


This is no longer strictly Arduino, since the processor is embedded directly in the circuitry

Yes it is. Arduino is not the board alone, it is the PCB, the IDE, the forum, the website and the bootloader. You're only missing one of those :wink:

I plan to make the single PCB version available assembled and tested if there is enough interest.

If you are interested, you can let me know, and register to be notified upon availability, by using the form here: Whole House Telephone Intercom Update.

A few first generation boards are now available:

Full details at Whole House Telephone Intercom Update

A ready-to-install commercial version of this intercom is now available, the Add-A-Com Whole House Intercom for Standard Telephone Systems.

Review and order from the product page at amazon.com:

A User Guide is available for download at Whole House Telephone Intercom Update