Hello, Mr. Watson
In the 1870s, the fastest way to send a message a long way was the telegraph. A telegraph sent short clicks over a wire. A trained operator turned the clicks into words. It was fast, but it could not carry a human voice.
Alexander Graham Bell, a teacher of deaf students, wanted to change that. He was fascinated by sound. He spent years studying how voices make the air vibrate. With his assistant, Thomas Watson, he worked in a Boston workshop. They tried to build a machine that could turn the vibrations of a voice into an electric signal.
On March 10, 1876, the two men were working in separate rooms. Bell spilled something on his clothes and called out, "Mr. Watson, come here, I want to see you." In the next room, Watson heard the words come through the wire. It was the first sentence ever spoken over a telephone.
Within a few years, telephones were spreading to homes and businesses in many cities. People could speak to someone far away as easily as to someone across the room. Today a phone fits in a pocket and can carry video as well as voices. But the main idea is the one Bell and Watson proved that day in Boston. A voice can be changed into a signal, sent along, and changed back into a voice.