How can I make a telephone using cups?

To make a telephone using cups, you will need two cups, a long piece of string, and a sharp object to poke holes in the cups. Poke a small hole in the bottom of each cup. Thread the string through the holes, tying a knot inside each cup to secure it. Pull the string tight and talk into one cup while the other person listens through the other cup. The vibrations of your voice will travel along the string, creating a simple telephone system.