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Home > Video > Video Display > Telephone History-Long Distance: “A Continent is Bridged” 1940 AT&T 1st Transcontinental Phone Line
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Telephone History-Long Distance: “A Continent is Bridged” 1940 AT&T 1st Transcontinental Phone Line

Telephones & Telephony playlist:  History, US History, United States History Playlist:  at “Man in bowler hat approached engineer in large office seated at desk. Engineer explains the basics of telephony and the future breakthroughs that need to take place in the technology. Engineer explains to layman visitor the basics of repeaters, amplifiers, and loading coils.- Camera zooms in on door with decal on foggy glass window “Repeater Development”; VS folders full of papers superimposed over shot of door, folders have Laboratories Folder labels, one folder after another fades in as other fades out, various subjects written on folders: repeater circuits theory general, vacuum tubes for wire transmission systems, repeaters on loaded telephone lines.- Great VS pan over engineer’s papers scattered on table filled with formulas, graphs and notes related to telephony.- Great VS men surveying land, and building and raising telephone poles and wiring them in the desert in open planes and desert, map of western United States superimposed over several shot. Great shot men putting wire up on telephone pole as men below post sign on pole San Francisco-New York Nevada-Utah State Line and wave an American flag, engineer puts American flag on top of telephone pole. (This is a historical reenactment of the completion of the transcontinental US long distance telephone network in 1915).”Reupload of a previously uploaded film with improved video & sound.Originally a public domain film from the US National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original). license:  repeater is an electronic device that receives a signal and retransmits it at a higher level or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances…UsageRepeaters are used to boost signals in coaxial and twisted pair cable and in optical fiber lines. An electrical signal in a cable gets weaker the further it travels, due to energy dissipated in conductor resistance and dielectric losses. Similarly a light signal traveling through an optical fiber suffers attenuation due to scattering and absorption. In long cable runs, repeaters are used to periodically regenerate and strengthen the signal…HistoryBefore the invention of electronic amplifiers, mechanically coupled carbon microphones were used as amplifiers in telephone repeaters. After the turn of the century it was found that negative resistance mercury lamps could amplify, and they were used. The invention of the audion tube in 1906 made transcontinental telephony practical. In the 1930s vacuum tube repeaters using hybrid coils became commonplace, allowing the use of thinner wires. In the 1950s negative impedance gain devices were more popular, and a transistorized version called the E6 repeater was the final major type used in the Bell System before the low cost of digital transmission made all voiceband repeaters obsolete. Frequency frogging repeaters were commonplace in frequency-division multiplexing systems from the middle to late 20th century.…In 1892, AT&T built an interconnected long-distance telephone network, which reached from New York to Chicago, the technological limit for non-amplified wiring. Users often did not use their own phone for such connections, but made an appointment to use a special long-distance telephone booth or “silence cabinet” equipped with 4-wire telephones and other advanced technology. The invention of loading coils extended the range to Denver in 1911, again reaching a technological limit. A major research venture and contest led to the development of the audion—originally invented by Lee De Forest and greatly improved by others in the years between 1907 and 1914—which provided the means for telephone signals to reach from coast to coast. Such transcontinental calling was made possible in 1914 but was not showcased until early 1915, as a promotion for the upcoming Panama-Pacific Exposition in San Francisco in the spring of the same year.On 25 January 1915, Alexander Graham Bell ceremonially sent the first transcontinental telephone call from 15 Dey Street in New York City, which was received by his former assistant Thomas A. Watson at 333 Grant Avenue in San Francisco. This process, nevertheless, involved five intermediary telephone operators and took 23 minutes to connect…
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