From Makezine.com | By Jason Poel Smith
In a SHTF situation, this may work as an alternative to purchasing a military field phone set and is much more affordable. All you need is some very basic electronic and soldering skills to complete the set-up and make it fully functional. Scaling it up to utilize on your property should then be fairly easy.
“An intercom can be a useful tool or a fun toy. In this project, I am going to show you how to make a simple intercom using a pair of old corded telephones. This is an easy electronics project that is great for beginners and fun to do with children…”