Do It YourSelf Telephone Intercom Device

This Picture Instructable reveals how to use two old mobile phone devices as a inexpensive intercom between Factor A and Factor B. Might be useful between the home and the store, between the treehouse and the ft, between your children's locations, etc.

This was initially build for my grade-school ladies to talk to each other on the phone between their bed rooms.

Basically it is a two-jack phone wall structure menu customized to act as the linking point for two expansion mobile phone devices. The menu relationships the two 'lines' together and resources energy. Two mobile phone devices are linked with their specific ports. Taking the mobile phone devices 'off hook' will allow the power supply power to energy the routine and you can carry on a discussion.

The power supply power are linked in sequence to provide 18V to energy the mobile phone devices. The power supply is not that great as I remember, so it may be beneficial to examine using an old notebook computer plug-in energy to energy it. I understand that some very old mobile phone devices may have polarity understanding so if the routine does not work try treating the power supply relationship to the wall structure ports.

The schematic reveals the relationships. Don't forget the 300 ohm resistor as proven. A call buzzer or light could be included with additional elements and electrical wiring to make the build more useful -- but for two pre-teens between bed rooms this was adequate.