?  Library of Wonders The Wonder of Sound

How come we can talk through a mobile phone?
Mobile phones work by changing your voice into an electric signal and sending that signal to the other person. But the electric signals are not sent directly through the air to the other person from your mobile phone. Electric signals from mobile phones can travel about 2 kilometers at most. So, the electric signals first travel to a base station within range of your mobile phone. Just like with regular telephones, telephone wires connect the base station to a base station near the other person. The base station near the other person sends the electric signals through the air to the other person’s mobile phone.

Your voice can be sent through the air either as an analog or digital electric signal. Mobile phones use digital electric signals. With digital electric signals, the vibrations in the air made by your voice are changed into numbers. Because they use numbers, digital electric signals can reach the other person without errors even in bad weather.