Joanne Barron, age 13, of St. Catharines, Ontario, Canada, for her question:
WHEN WAS THE ATLANTIC UNDERSEA CABLE DEVELOPED?
Undersea communications cables link North America with Asia, Australia, Central America and South America. The leading and most important intercontinental cable routes stretch under the north Atlantic Ocean. A large number of separate transatlantic cable systems now link Europe with North America.
A single telephone cable can carry 138 conversations across the Atlantic at one time. Cables help to make quick communication possible over long distances. Thick ones stretched under our oceans are used to transmit radio and television programs, pictures, maps and telephone and telegraph messages.
As early as 1840 attempts had been made to lay cables underwater. All the early tries were unsuccessful until cable makers started using a rubber like substance called gutta percha as insulation.
In 1851 two English brothers named John and Jacob Brett laid a gutta percha cable under the English Channel. In 1856 an American businessman named Cyrus Field laid an undersea cable across Canada's Cabot Strait from Cape Ray, Newfoundland, to Cape Breton Island in Nova Scotia.
U.S. Navy engineers discovered that the ocean floor between Newfoundland and Ireland was fairly level and made up of soft mud. This part of the ocean, therefore, was ideal as a route for a transatlantic cable.
Cyrus Field's Atlantic Telegraph Company tried for many years to put an Atlantic telegraph cable into operation. The first two cables broke, but in 1856 the U.S. warship Niagara and the British warship Agamemnon laid a cable for Field that did not break. Unfortunately, it failed after only four weeks of operation because signals became extremely weak and distorted. A fourth cable in 1865 broke and sank just as the project was almost completed, but success came on July 27, 1866, with an undersea cable stretching from Valencia, Ireland, to Hearts Content, Newfoundland. Signals traveled clearly over the cable.
By 1900, 15 cables had been laid across the Atlantic. Improved sending and receiving techniques were developed and by 1930 it was possible to send up to 400 words a minute across the Atlantic. By the mid 1960s, messages could be sent at the rate of 2,500 ~kTords per minute.
First transatlantic telephone cable was laid in 1956, going 2,250 miles from Clarenville, Newfoundland, to Oban, Scotland. Early cables could carry messages only in one direction, but by 1963 a two way cable was developed.
Repeaters spliced into undersea cables amplify voice signals about 100,000 times. Inside each repeater are more than 5,000 precision parts.