How does your voice travel in a phone call?

You say ‘hello’ in Kochi and someone in Dubai hears it a fraction of a second later. In between, your voice changes form several times.

First, the microphone turns the sound waves of your voice into an electrical signal. Your phone then converts that signal into digital data — millions of ones and zeros — and squeezes it smaller so it travels faster.

Your phone sends this data by radio waves to the nearest mobile tower. From the tower, it runs through fibre-optic cables as pulses of light, under cities and across the sea floor. Submarine cables, not satellites, carry almost all international calls.

At the far end, the process reverses: light becomes data, data becomes an electrical signal, and the speaker turns it back into sound. The whole round trip takes less time than a blink.