Telephone!

3. The number of waves produced within a given period of time. The frequency of a sound wave determines its pitch.
5. The method of sending light-signals at very high speed through thin glass or plastic tubes bundled together.
7. A way of changing continuous electrical current into a sequence of "0" and "1" (on/off) electrical signals.
9. A substance that allows electricity to flow through it easily.
11. The flow of electrons along a conductor, such as a wire.
12. The invisible force that attracts some metals and is given out by an electric current as well as by some substances.

1. A device containing two substances that react chemically to produce electricity.
2. The complete path taken by an electrical current along a suitable conductor.
4. A magnet which works only when a current passes through a coil of wire wrapped around an iron core.
6. A flexible layer, like a skin, which vibrates in air and in a microphone that can send and receive sound waves.
8. A common natural material - coal, charcoal, and diamonds are forms of carbon.
10. A system for changing one kind of information (such as sounds) into another (such as electrical signals).