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Alexander Graham Bell biography
Dátum pridania: 21.11.2002 Oznámkuj: 12345
Autor referátu: aradvan
 
Jazyk: Angličtina Počet slov: 3 202
Referát vhodný pre: Stredná odborná škola Počet A4: 11.1
Priemerná známka: 2.97 Rýchle čítanie: 18m 30s
Pomalé čítanie: 27m 45s
 

With a group of associates, including the American inventor and aviator Glenn Hammond Curtiss, Bell developed the aileron, a movable section of an airplane wing that controls roll. They also developed the tricycle landing gear, which first permitted takeoff and landing on a flying field. Applying the principles of aeronautics to marine propulsion, his group started work on hydrofoil boats, which travel above the water at high speeds. His final full-sized "hydrodrome," developed in 1917, reached speeds in excess of 113 km/h (70 mph) and for many years was the fastest boat in the world.

Bell's continuing studies on the causes and heredity of deafness led to experiments in eugenics, including sheep breeding, and to his book Duration of Life and Conditions Associated with Longevity (1918). He died on August 2, 1922, at Baddeck, where a museum containing many of his original inventions is maintained by the Canadian government.


Telegraph, system of communication employing electrical apparatus to transmit and receive signals in accordance with a code of electrical pulses. Originally the term telegraphy referred to any form of communication over long distances in which messages were transmitted by signs or sounds.


II. The Morse Telegraph

The first electrical instruments for telegraphic transmission were invented in the United States by the American inventor Samuel F. B. Morse in 1837 and in Britain the same year by the British physicist Sir Charles Wheatstone in collaboration with the British engineer Sir William F. Cooke. Morse used a simple code in which messages were transmitted by electric pulses passing over a single wire (see Morse Code, International). Morse's apparatus, which sent the first public telegram in 1844, resembled a simple electric switch. It allowed current to pass for a prescribed length of time and then shut it off, all at the pressure of a finger. The original Morse receiver had an electromagnetically controlled pencil that made marks on paper tape moving over a clockwork-operated cylinder. The marks varied with the duration of the electric current passing through the wires of the electric magnet and took the written form of dots and dashes.

While experimenting with his instrument, Morse found that signals could be transmitted successfully for only about 32 km (20 mi). Beyond that distance the signals grew too weak to be recorded. Morse and his associates therefore developed a relay apparatus that could be attached to the telegraph line 32 km from the signal station to repeat signals automatically and send them an additional 32 km. The relay consisted of a switch operated by an electromagnet.
 
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