Here's one of the simplest means of voice communication ever devised. You can prepare and use it yourself without any cost.

Materials Needed

All you will need are two round cardboard boxes, such as are commonly used for oatmeal or salt, and a stout piece of string or thin cord, of the desired length-10 to 20 feet or more. You can also use tin cans and a thin, single-strand wire, uninsulated.

How to Proceed

Remove one end from each of the boxes. Punch a tiny hole in each of the remaining ends, and pass the string through these, knotting it at the ends, inside the covers, so it will not pull through.

How to Use

Two boys stand apart the length of the string, perhaps in two separate rooms. One puts the open end of his box over his mouth and speaks into it slowly and distinctly. At the same time, the other boy holds the other box to his ear.

How It Works

The voice is caught by the first box held over the mouth; the sound vibrates along the stretched string and is heard distinctly in the box at the other end.

For a two-way conversation, simply reverse the process, whereby the first boy holds the box-receiver up to his ear, while the other boy talks through his box-transmitter.