working of telephone?

Three critical developments were necessary precursors to the invention of the telephone. First was the understanding that an electrical current can create a magnetic field, and therefore mechanical or acoustic energy. This is credited to Danish physicist Christian Oersted in 1820, who demonstrated that a compass needle can be manipulated by running an electric wire over it. Second was the understanding that the reverse is possible - electrical induction - that is, generating a current by placing a moving magnet next to a wire. This insight is credited to inventor Michael Faraday in the year of 1821. The last necessary development was that of the battery, a chemical device capable of producing a continuous source of electricity. The first very crude battery was the "Leyden jar", a device for storing static electricity invented by two Dutchmen in 1746. Voltaire and others developed more sophisticated batteries throughout the 18th and 19th centuries.

Often considered second in impact only to the printing press for revolutionizing human communication, the telephone made it possible to connect people to others without dependency on the postal service. Every domain of human affairs, from business to daily life, was changed radically and permanently. Globally, the telephone has saved humanity trillions of dollars in communications costs. The basic design of the telephone has not changed since its initial invention.

http://www.wisegeek.com/how-does-a-telep... Learn the working of telephone with animation and drawings here:

http://electronics.howstuffworks.com/tel...

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