HOW DOES A TELEPHONE WORK?

Telephones transmit speech messages along wires by means of electrical signals. They were invented as long ago as 1876. In the handset of a telephone are a loudspeaker and a very small microphone, which contains granules of carbon. When you talk into the microphone the sound waves of your voice […]

HOW DO RADIOS WORK?

Radio signals are transmitted using a carrier wave. Radio waves form part of the electromagnetic spectrum. Radio waves with the longest wavelengths are bounced off a layer high up in the Earth’s atmosphere, called the ionosphere. In this way radio messages can be bounced for very long distances. A radio […]