Hi there. What happens is that the voice signal is broken up into small packets of electrical data. This data can travel between computers along telephone wire, fibre-optic cable, or through the air in microwaves, or bounced off satelites by laser or microwave. Most of these are specialist computers just for the telephone system, but it can work over the internet too.
So long as enough of the packets make it to the destination fast enough, you can hear clear speech.
At one time all calls were carried down wires from one phone to another. That’s why long-distance calls took longer to route and were more expensive to make. International calls took so long to route that there was a very noticeable (and quite confusing) delay between you and the person at the other end, which was caused by the time it took for signals to travel down the wire. Which was kinda frustrating coz you’d be like “hey do you wanna come out tonight?” and then you’d be waiting ages so you’d say “shall we bomb Poland?” and then they would be like “yeah, in half an hour?” – and then you’d bomb Poland when really you were meant to go to the cinema…
OK so where was !?
Now, calls travel in a whole variety of different ways. Most calls still go from homes to local exchanges along old-style copper wires (arranged in what’s called a twisted pair). But calls can travel between exchanges down ultra-fast, high-capacity fibre-optic cables. Longer-distance calls are often beamed between towns using microwave towers (like small satellite dishes mounted on high buildings). International calls are typically bounced around the world using space satellites. Fibre-optics, microwave towers, and satellites send and receive phone calls not as electrical signals but as pulses of electromagnetic radiation (light or radio waves) travelling at the speed of light. That’s why modern international phone calls are much faster, cheaper, and more reliable than they used to be—and why there’s hardly any time lag on calls anymore! So we don’t bomb Poland….