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Telephone

Invented by: Alexander Graham Bell
Nationality: Scottish
Date: 1876
 
     Alexander Graham Bell was a doctor. He workea with deaf children and understood the way sounds caused vibrations.
     While only in his 20's, he discovered a way of converting vibrations into variations in electric current - and back again.
     His telephone had a diaphragm (a thin metal sheet) which vibrated when spoken to; close behind the diaphragm was an electromagnet which converted the vibrations into electric signals.
     Bell's telephone had a single transmitter  receiver: when you had finished speaking into the microphone you held it to your ear and listened to the other person's voice.
     In 1877, Thomas Edison invented a better, separate, microphone using carbon granules behind the diaphragm. Apart from that, today's telephone is as Bell invented it.
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  Electric Light Bulb
 
Tape Recorder
(and Walkman)

Television

Cameras  in the Beginning

Aqualung

Telephone 2

The Radio

 



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