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

--Phil.

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?

Quote:


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

A few first generation boards are now available:


Full details at http://joes.com/intercom/update.html