The main elements necessary for the telephone were available at least a third of a century before it was actually invented in Boston, 1876 by Alexander Graham Bell. Although all that needed to be known for the invention of the telephone was known, it took more than 40 years to pass before the telephone was actually to appear. This was due to the fact that it was not a big enough social need until later times. Many inventors have failed to appreciate the potential of instruments they had designed, but Alexander Bell appears to have been the first to understand not only that the electrical transmission of voice was possible but that it was commercially practical as well.
The principles of the telephone are the same today as they were in the 19th century. The voice vibrates the air, which vibrates a diaphragm. The motion of the diaphragm makes a identical vibration in an electric current. In the ordinary modern telephone, the diaphragm presses against an collection of carbon particles and causes their electrical resistance to vary, so that an electric current flowing through the particles is changed and waves in accordance with the pressure on the particles. At the receiver, the current flows through an electromagnet. As the power of this magnet fluctuates, so does its attraction for an adjacent steel diaphragm. The diaphragm vibrates, moving the air and producing sound.
The telephone has gradually replaced the telegraph as the main system of telecommunications. Not only does the telephone serve as an instrument for reproducing fluent speech and other sounds at a distance by the means of electric waves but its circuits carry telegraph, telephoto, and television signals and data in a form that can be fed
directly into processing devices. In effect, telephone circuits enable computers at remote points to communicate with each other. As a result, telephone systems have become an essential part of modern telecommunications systems in general.
Bibliography:
Britannica
World Book
Encarta
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Как писать рефераты Практические рекомендации по написанию студенческих рефератов. |
| ! | План реферата Краткий список разделов, отражающий структура и порядок работы над будующим рефератом. |
| ! | Введение реферата Вводная часть работы, в которой отражается цель и обозначается список задач. |
| ! | Заключение реферата В заключении подводятся итоги, описывается была ли достигнута поставленная цель, каковы результаты. |
| ! | Оформление рефератов Методические рекомендации по грамотному оформлению работы по ГОСТ. |
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