Ever wanted to reuse those old telephones and or modems using just two wires. This instructable shows you several options. Get a continuity tester to make your job easier.
Step 1: Circuit 1.
This first circuit if you just want to use a battery. For short distances use the nine volt battery for compactness.
Step 2: Circuit 2.
This circuit is for using a wallwart. Better for a more permanent setup. Originally I intended to use coax but any 2 line wire will do.
Step 3: Circuit 3.
This is for a more permenant circiut and with buzzer. As soon as you pick up the phone the buzzer should sound. Thanx to Markus Wandel.