We all have old phones. Why not turn them into an intercom for your kids tree house. Or turn two old cordless phones into home base walkie talkie. Here is how.
Step 1: Materials
In-Line coupler (I got mine at Frys for 1.49)
9 volt connector (radio shack, or cut it out of some old piece of junk)
milk (helps keep you hydrated and keeps bones strong)
300 ohm resistor or close to it
black electrical tape
two telephone cords. (CAT 1 cable)
Step 2: Open your coupler
Apply pressure to break it open at the center, in the same way you might break a twig. You may press it up against the side of your desk if it helps. You will see 4 wires, they should be color coded red, green, yellow and black. If they are not, it will be harder. The red and green cables are the one you should worry about. The other two are for the second line; it will not affect this project at all.