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The phone is a telecommunications device designed to transmit audio signals via electrical signals from a distance.
For a long time was considered Alexander Graham Bell invented the telephone , along with Elisha Gray. However Graham Bell was not the inventor of this device , but only the first to patent it. This happened in 1876. The June 11, 2002 the U.S. Congress adopted resolution 269 ,which recognized that the inventor of the telephone was Antonio Meucci , who called teletrofono , and Alexander Graham Bell. In 1871 Meucci could only by economic difficulties, present a brief description of his invention , but not to formalize the patent before the Patent Office of the United States.
History of his invention
 Around 1857 Antonio Meucci constructed a telephone to connect your officewith your bedroom , located on the second floor , due to rheumatism of his esposa.1 however lacked enough money to patent his invention , so he presented to a company (Western Union, who promoted the "invention" of Graham Bell) who paid no attention , but which also returned the materials.
In 1876 , having discovered that to transmit human voice could only use a direct current , Scottishinventor nationalized in U.S. Alexander Graham Bell , built and patented a few hours before Elisha Gray fellow first phone capable of transmitting and receiving human voice in all its quality and timbre. Nor should leave out Thomas Alva Edison, who introduced major improvements in the system , including the microphone is carbon granules .
The June 11, 2002 the U.S. Congress adopted resolution 269 ,which recognized that the inventor of the telephone was Antonio Meucci and Alexander Graham Bell. The resolution , adopted unanimously , U.S. officials estimate that "the life and work of Antonio Meucci should be recognized legally , and that his work in the invention of the telephone should be admitted ." According to the text of this resolution , Antonio Meucci installed a rudimentarytelecommunications device from the basement of his home in Staten Island ( New York ) and his wife 's room , on the first floor .
Evolution of the phone and use •
Panasonic Digital Phone .
Since its original conception successive improvements have been introduced in both the handset itself and the methods and systems of network operation .
In regard to the own telephone , several things can be noted :
Theintroduction of the carbon microphone , which significantly increased the output power , and therefore the maximum range of communication.
Luink antilocal device to avoid hearing disturbance caused by ambient noise of the room where the phone is installed .
Pulse dialing using the dial disc called .
Touchtone dialing .
The introduction or electret microphone electret condenser microphone ,practically used in all modern appliances that dramatically improves the sound quality .
In terms of methods and systems for operating the telephone network can be noted:
The fixed or conventional , which is one that refers to the lines and equipment that are responsible for communication between non-portable telephone terminals , and generally linked together or with central metal conductors .The manual switching telephone exchange to interconnect through the intervention of an operator / a different phone ( Harlond ) , thereby creating a first network model . First were the manuals central Local Battery (phones powered by batteries ) and were subsequently manuals Battery power center ( phone powered from the exchange) .
The introduction of automatic switching exchanges , constituted byelectromechanical devices of which have existed and still exist in some cases , various systems : rotary switching system ( in Spain systems 7A1 , 7A2 , 7D , 7BR , AGF ) , and system crossbar switch ( in Spain : Pentaconta Systems 1000 , PC32 , ARF ) and other more complex .
The electromechanical automatic switching centers , but controlled by computer. Also called central semielectrónicas (...