Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an American inventor and businessman who developed many important devices. Thomas Edison was born in Milan, Ohio and grew up in Port Huron, Michigan. Partially deaf since adolescence, he became a telegraph operator in the 1860s, and a famously fast one. Some of his earliest inventions related to electrical telegraphy, including a stock ticker.

Edison's major innovation was the Menlo Park research lab, which was built in New Jersey. It was the first institution set up with the specific purpose of producing constant technological innovation and improvement. Edison was the inventor of most of the inventions produced there, though he primarily supervised the operation and work of his employees.

Most of Edison's patents were utility patents, with only about a dozen being design patents. Many of his inventions were not completely original, but improvements which allowed for mass production. For example, contrary to public perception, Edison did not invent the electric light bulb. Several designs had already been developed by earlier inventors including Joseph Swan, Henry Woodward, Mathew Evans, James Bowman Lindsay, William Sawyer, and Heinrich Göbel. In 1878, Edison applied the term filament to the element of glowing wire carrying the current, although English inventor Joseph Swan used the term prior to this. Edison took the features of these earlier designs and set his workers to the task of creating longer-lasting bulbs. After Edison purchased the Woodward and Evans patent of 1875, his employees experimented with a large number of different materials to increase the bulb's burning time. By 1879, they had increasied the burning time enough to make the light bulb commercially viable. While the earlier inventors had produced electric lighting in laboratory conditions, Edison concentrated on commercial application and was able to sell the concept to homes and businesses by mass-producing relatively long-lasting light bulbs and creating a system for the generation and distribution of electricity.

The Menlo Park research lab was made possible by the sale of the quadruplex telegraph that Edison invented in 1874. The quadruplex telegraph could send four simultaneous telegraph signals over the same wire. When Edison asked Western Union to make an offer, he was shocked at the unexpectedly large amount that Western Union offered; the patent rights were sold for $10,000. The quadruplex telegraph was Edison's first big financial success.

During the initial years of electricity distribution, Edison's DC was the standard for the United States, and Edison was not disposed to lose all his patent royalties. During the "War of Currents" era, Serbian immigrant Nikola Tesla and Edison became adversaries due to Edison's promotion of DC for electric power distribution over the more efficient alternating current (AC) advocated by Tesla, who patented AC in Graz, Austria. Edison (or, reportedly, one of his employees) employed the tactics of misusing Tesla's patents to construct the first electric chair for the state of New York to promote the idea that AC was deadly. Popular myth has it that Edison invented the electric chair, despite being against capital punishment, solely as a means of impressing the public that AC was more dangerous than DC. In fact, like most of the output of the Menlo Park operations, the chair was primarily invented by a few of his employees, in particular Harold P. Brown, while Edison supervised their operations. [1] (http://inventors.about.com/library/weekly/aa102497.htm)

Edison went on to carry out a campaign to discredit and discourage the use of AC. Edison presided personally over several electrocutions of animals, primarily stray cats and dogs, for the benefit of the press to prove that his system of DC was safer than that of AC. Edison's series of animal executions peaked with the electrocution of Topsy the Elephant.

Many of Edison's inventions using DC ultimately lost to AC devices proposed by others. AC distribution systems replaced DC, enormously extending the range and improving the safety and efficiency of power distribution. Since the 1950s, high voltage direct current (HVDC) transmission systems have become more common in certain situations.

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