An Underwater Cable ~ 1939 American Telephone & Telegraph (AT&T)

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Laying of an underwater telephone cable between San Francisco and Oakland, California.

Originally a public domain film from the Library of Congress Prelinger 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).

https://en.wikipedia.org/wiki/Submarine_communications_cable

Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/

A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables laid beginning in the 1850s carried telegraphy traffic, establishing the first instant telecommunications links between continents, such as the first transatlantic telegraph cable which became operational on 16 August 1858. Subsequent generations of cables carried telephone traffic, then data communications traffic. Modern cables use optical fiber technology to carry digital data, which includes telephone, Internet and private data traffic.

Modern cables are typically about 1 inch (25 mm) in diameter and weigh around 2.5 tons per mile (1.4 tonnes per km) for the deep-sea sections which comprise the majority of the run, although larger and heavier cables are used for shallow-water sections near shore...

Early history: telegraph and coaxial cables

First successful trials

After William Cooke and Charles Wheatstone had introduced their working telegraph in 1839, the idea of a submarine line across the Atlantic Ocean began to be thought of as a possible triumph of the future. Samuel Morse proclaimed his faith in it as early as 1840, and in 1842, he submerged a wire, insulated with tarred hemp and India rubber, in the water of New York Harbor, and telegraphed through it. The following autumn, Wheatstone performed a similar experiment in Swansea Bay. A good insulator to cover the wire and prevent the electric current from leaking into the water was necessary for the success of a long submarine line. India rubber had been tried by Moritz von Jacobi, the Prussian electrical engineer, as far back as the early 19th century.

Another insulating gum which could be melted by heat and readily applied to wire made its appearance in 1842. Gutta-percha, the adhesive juice of the Palaquium gutta tree, was introduced to Europe by William Montgomerie, a Scottish surgeon in the service of the British East India Company. Twenty years earlier, Montgomerie had seen whips made of gutta-percha in Singapore, and he believed that it would be useful in the fabrication of surgical apparatus. Michael Faraday and Wheatstone soon discovered the merits of gutta-percha as an insulator, and in 1845, the latter suggested that it should be employed to cover the wire which was proposed to be laid from Dover to Calais. It was tried on a wire laid across the Rhine between Deutz and Cologne. In 1849, C.V. Walker, electrician to the South Eastern Railway, submerged a two-mile wire coated with gutta-percha off the coast from Folkestone, which was tested successfully...

In August 1850, having earlier obtained a concession from the French government, John Watkins Brett's English Channel Submarine Telegraph Company laid the first line across the English Channel, using the converted tugboat Goliath. It was simply a copper wire coated with gutta-percha, without any other protection, and was not successful... in September 1851, a protected core, or true, cable was laid by the reconstituted Submarine Telegraph Company from a government hulk, the Blazer, which was towed across the Channel.

In 1853, more successful cables were laid, linking Great Britain with Ireland, Belgium, and the Netherlands, and crossing The Belts in Denmark...

Transatlantic telegraph cable

The first attempt at laying a transatlantic telegraph cable was promoted by Cyrus West Field, who persuaded British industrialists to fund and lay one in 1858. However, the technology of the day was not capable of supporting the project; it was plagued with problems from the outset, and was in operation for only a month. Subsequent attempts in 1865 and 1866 with the world's largest steamship, the SS Great Eastern, used a more advanced technology and produced the first successful transatlantic cable. Great Eastern later went on to lay the first cable reaching to India from Aden, Yemen, in 1870...