Whole House Telephone Intercom Update
Would you like a Whole House Telephone Intercom of your own, but without building custom circuitry or dedicating an Arduino board? Introducing the Add-A-Com Whole House Intercom for Standard Telephone Systems. Our first run is sold out, so it is no longer available from this amazon.com product page as of 1/20/11.
This commercial version features a jumper to enable/disable the call hold and transfer feature, another jumper to support stand-alone operation, a more efficient power supply that requires no heat sink, and a more robust ringing signal. It is supplied with everything you need for a typical installation - nothing else to buy. For an overview of benefits, and how this intercom compares with other wired and wireless units, see here. For details on installation and operation, you can download this User Guide.