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First telephone call. Engraving of Alexander Graham Bell (lower frame) making the first-ever telephone call to his assistant Thomas Watson. On 10 March 1876 Bell said "Watson, come here; I want you", after spilling acid on his clothes. The telephone's transmitter and receiver had an identical design. The transmitter had an iron diaphragm which converted sound waves into an oscillating electric current. The receiver's diaphragm converted this current back into sound waves. Bell's discovery made him a rich man and led to the formation of the Bell Telephone Company which was to become the world's largest private service organisation.
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