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How was the telephone invented? The story of the invention of the telephone is a very dramatic one. (No wonder they were able to make a movie about it!) But first let's make sure we understand the principle of how a telephone works. When you speak, the air makes your vocal cords vibrate. These vibrations are passed on to the air molecules so that sound waves come out of your mouth, that is, vibrations in the air. These sound waves strike an aluminum disk or diaphragm in the transmitter of your telephone. And the disk vibrates back and forth in just the same way the molecules of air are vibrating. These vibrations send a varying, or undulating, current over the telephone line. The weaker and stronger currents cause a disk in the receiver at the other end of the line to vibrate exactly as the diaphragm in the transmitter is vibrating. This sets up waves in the air exactly like those which you sent into the mouthpiece. When these sound waves reach the ear of the person at the other end, they have the same effect as they would have if they came directly from your mouth! Now to the story of Alexander Graham Bell and how he invented the telephone. On June 2, 1875, he was experimenting in Boston with the idea of sending several telegraph messages over the same wire at the same time. He was using a set of spring-steel reeds. He was working with the receiving set in one room, while his assistant, Thomas Watson, operated the sending set in the other room. Watson plucked a steel reed to make it vibrate, and it produced a twanging sound. Suddenly Bell came rushing in, crying to Watson: "Don't change anything. What did you do then? Let me see." He found that the steel rod, while vibrating over the magnet, had caused a current of varying strength to flow through the wire. This made the reed in Bell's room vibrate and produce a twanging sound. The next day the first telephone was made and voice sounds could be recognized over the first telephone line, which was from the top of the building down two flights. Then, on March 10 of next year, the first sentence was heard: "Mr. Watson, come here, I want you." For Details
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