Скачать или смотреть 29th July 1914: Successful voice test of the first transcontinental telephone line

By 1892 the American Telephone and Telegraph Company, better known as AT&T, had successfully constructed a telephone line between New York and Chicago. Made of copper cable, it was technologically impossible to go any further due to distortion of the electrical signals over longer distances. However, the creation of the loading coil in 1899 allowed signals to travel further and, by 1911, the telephone network stretched from New York to Denver.

Desperate to find a way to improve the signal further and enable the construction of a transcontinental telephone line, AT&T were introduced to Dr. Lee De Forest’s three-element vacuum tube known as an Audion. Although originally intended to be a radio receiver detector, AT&T’s scientists found that they could improve the design for it to function as a telephone line repeater.

AT&T soon bought the patent from De Forest and, having implemented the changes suggested by Dr. Harold Arnold, began to install the new high-vacuum amplifier tubes. The telephone network soon spread beyond Denver and, on 17 June 1914, the final pole was erected at Wendover, Utah marking the completion of the line.

The first transcontinental voice test was conducted on 29 July by Theodore Vail, the president of AT&T. However, the line didn’t begin commercial operation until 25 January 1915, in the midst of the Panama–Pacific International Exposition. The event was marked by Alexander Graham Bell in New York speaking to his assistant, Thomas Watson, who was in San Francisco. He repeated his famous words, ‘Mr. Watson, come here. I want you,’ to which Watson replied, ‘It will take me five days to get there now!’