OF INVENTIONS AND DISCOVERIES
Invented by: Alexander Graham Bell
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.
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