Alexander Graham Bell (March 3, 1847 August 2, 1922) was a scientist, inventor, and founder of Bell Canada, who was known as the formerly credited as father of the telephone. In addition to his work in telecommunications technology, he was responsible for important advances in aviation and hydrofoil technology.

Biography
Born Alexander Bell in Edinburgh, Scotland, he later adopted the middle name Graham out of admiration for Alexander Graham, a family friend.
His family was associated with the teaching of elocution: his grandfather in London, his uncle in Dublin, and his father, Alexander Melville Bell, in Edinburgh, were all professed elocutionists. The latter has published a variety of works on the subject, several of which are well known, especially his treatise on Visible Speech, which appeared in Edinburgh in 1868. In this he explains his method of instructing deaf mutes, by means of their eyesight, how to articulate words, and also how to read what other persons are saying by the motions of their lips.
Alexander Graham Bell was educated at the Royal High School of Edinburgh, from which he graduated at the age of 13. At the age of 16 he secured a position as a pupil-teacher of elocution and music in Weston House Academy, at Elgin in Morayshire. The next year he spent at the University of Edinburgh. From 1866 to 1867, he was an instructor at Somersetshire College at Bath, England. While still in Scotland he is said to have turned his attention to the science of acoustics, with a view to ameliorate the deafness of his mother.
In 1870, he moved with his family to Canada where they settled at Brantford, Ontario. Before he left Scotland, Bell had turned his attention to telephony, and in Canada he continued an interest in communication machines. He designed a piano which could transmit its music to a distance by means of electricity. In 1873, he accompanied his father to Montreal, Quebec, where he was employed in teaching the system of visible speech. The elder Bell was invited to introduce the system into a large day-school for mutes at Boston, but he declined the post in favor of his son, who became Professor of Vocal Physiology and Elocution at Boston University's School of Oratory.
At Boston University he continued his research in the same field, and endeavored to produce a telephone which would not only send musical notes, but articulate speech. With financing from his American father-in-law, on March 7, 1876, the U.S. Patent Office granted him Patent Number 174,465 covering "the method of, and apparatus for, transmitting vocal or other sounds telegraphically ... by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound", the telephone.
After obtaining the patent for the telephone, Bell continued his many experiments in communication, which culminated in the invention of the photophone-transmission of sound on a beam of light — a precursor of today's optical fiber systems. He also worked in medical research and invented techniques for teaching speech to the deaf. The range of Bell's inventive genius is represented only in part by the eighteen patents granted in his name alone and the twelve he shared with his collaborators. These included fourteen for the telephone and telegraph, four for the photophone, one for the phonograph, five for aerial vehicles, four for hydroairplanes, and two for a selenium cell.
In 1882, he became a naturalized citizen of the United States. In 1888, he was one of the founding members of the National Geographic Society and became its second president. He was the recipient of many honors. The French Government conferred on him the decoration of the Légion d'honneur (Legion of Honor), the Académie française bestowed on him the Volta Prize of 50,000 francs, the Royal Society of Arts in London awarded him the Albert medal in 1902, and the University of Würzburg, Bavaria, granted him a Ph.D. He was awarded the AIEE's Edison Medal in 1914 for "For meritorious achievement in the invention of the telephone."
Bell married Mabel Hubbard, who was one of his pupils at Boston University, on July 11, 1877. He died at his estate at Beinn Bhreagh, near Baddeck, Nova Scotia, in 1922 and is buried alongside his wife atop Beinn Bhreagh Mountain overlooking Bras d'Or Lake. He was survived by two of their four children.
In a testament to Bell's internationality, he was named one of the top ten Greatest Canadians, Greatest Britons, and "American Greats".

Inventions
Bell was a prolific inventor, and had a keen interest in many fields.

The telephone and patent issues
Bell filed an application to patent his speaking telephone in the United States on February 14, 1876, and by a strange coincidence, Mr. Elisha Gray applied on the same day for patent caveat (a preliminary notice of a patent application) of a similar kind only 2 hours after Bell had filed for his patent.
Gray's transmitter is supposed to have been suggested by the very old device known as the "lovers' telephone," in which two diaphragms are joined by a taut string and in speaking against one the voice is conveyed through the string, solely by mechanical vibration, to the other. Gray employed electricity, and varied the strength of the current in conformity with the voice by causing the diaphragm in vibrating to dip a metal probe attached to its centre more or less deep into a well of conducting liquid in circuit with the line. As the current passed from the probe through the liquid to the line a greater or less thickness of liquid intervened as the probe vibrated up and down, and thus the strength of the current was regulated by the resistance offered to the passage of the current. His receiver was an [electromagnet]having an iron plate as an armature capable of vibrating under the attractions of the varying current.
But Gray allowed his idea to slumber, whereas Bell continued to perfect the apparatus designed by Gray. An official at the patent office later admitted to selling Gray's idea to Bell's lawyers for money. Gray never knew this. However, when Bell achieved an unmistakable success, Gray brought a suit against him, which resulted in a compromise, one public company acquiring both patents.
Philipp Reis, a German self-taught scientist and inventor, also worked on a version of the telephone many years before Bell. Reis' telephone was fairly crude and roused little interest in the scientific community, but his work appears to have been used by Bell when designing the telephone. [1]
Of the people who have challenged Bell's patent and claimed to have invented the telephone, the most interesting case was that of Antonio Meucci, an Italian emigrant, who produced a mass of evidence to show that in 1849, while in Havana, Cuba, he experimented with the view of transmitting speech by the electric current. He continued his research in 1852-1853, and subsequently at Staten Island, U.S.; and in 1860 deputed a friend visiting Europe to interest people in his invention. In 1871, he filed a caveat in the United States Patent Office and tried to get Mr Grant, President of the New York District Telegraph Company, to give the apparatus a trial. Ill health and poverty, from injuries of an explosion on board the Staten Island ferry boat Westfield, retarded his experiments and prevented him from completing his patent.
Meucci's experimental apparatus was exhibited at the Philadelphia Exhibition of 1884 and attracted much attention. But his evidence showed lack of electrical understanding and incomplete models. In the caveat of 1871, he says "I employ the well-known conducting effect of continuous metallic conductors as a medium for sound, and increase the effect by electrically insulating both the conductor and the parties who are communicating. It forms a speaking telegraph without the necessity of any hollow tube" . Meucci was eventually recognised as the original inventor of the telephone by the Congress of the United States in Resolution 269, dated June 11, 2002.

Bell Telephone Company
Bell and others formed the Bell Telephone Company in July 1877. In 1879, it merged with the New England Telephone Company forming the National Telephone Company, which was renamed the American Bell Telephone Company in 1880. Along with Thomas Edison, Bell formed the Oriental Telephone Company on January 25, 1881. On March 3, 1885, American Telephone and Telegraph Company (AT&T) was formed to manage the expanding long-distance business of the American Bell Telephone Company. AT&T became the overall holding company for all the Bell ventures, and remains active today.

Bel and decibel
The bel is a unit of measurement invented by Bell Labs and named after Bell. The bel was too large for everyday use, so the decibel (dB), equal to 0.1 B, became more commonly used. Now, dB is commonly used as a unit for measuring the sound intensity.

The photophone
Another of Bell's inventions was the photophone, a device enabling the transmission of sound over a beam of light, which he developed together with Charles Sumner Tainter. The device employed light-sensitive cells of crystalline selenium, which has the property that its electrical resistance varies inversely with the illumination (i.e., the resistance is higher when the material is in the dark, and lower when it is lighted). The basic principle was to modulate a beam of light directed at a receiver made of crystalline selenium, to which a telephone was attached. The modulation was done either by means of a vibrating mirror, or a rotating disk periodically obscuring the light beam.
This idea was by no means new. Selenium had been discovered by Jöns Jakob Berzelius in 1817, and the peculiar properties of crystalline or granulate selenium were discovered by Willoughby Smith in 1873. In 1878, one writer with the initials J.F.W. from Kew described such an arrangement in Nature in a column appearing on June 13, asking the readers whether any experiments in that direction had already been done. In his paper on the photophone, Bell credited one A. C. Browne of London with the independent discovery in 1878—the same year Bell became aware of the idea. Bell and Tainter, however, were apparently the first to perform a successful experiment, by no means any easy task, as they even had to produce the selenium cells with the desired resistance characteristics themselves.
In one experiment in Washington, D.C. the sender and the receiver were placed on in different buildings some 700 feet (213 metres) apart. The sender consisted of a mirror directing sunlight onto the mouthpiece, where the light beam was modulated by a vibrating mirror, focused by a lens and directed at the receiver, which was simply a parabolic reflector with the selenium cells in the focus and the telephone attached. With this setup, Bell and Tainter succeeded to communicate clearly.
The photophone was patented on December 18, 1880, but the quality of communication remained poor and the research was not pursued by Bell.