Editing Submarine communications cable (section)

===Transatlantic telephony===
[[File:Submarine Telephone Cables PICT8182 1.JPG|thumb|right|<!--Five is dubious, I count only three – but then again I might be blind...-->Submarine communication cables crossing the Scottish shore at Scad Head on [[Hoy, Orkney|Hoy]], Orkney.]]

While laying a transatlantic telephone cable was seriously considered from the 1920s, the technology required for economically feasible telecommunications was not developed until the 1940s. A first attempt to lay a "[[pupinize]]d" telephone cable—one with loading coils added at regular intervals—failed in the early 1930s due to the [[Great Depression]].

[[TAT-1]] (Transatlantic No. 1) was the first [[transatlantic telephone cable]] system. Between 1955 and 1956, cable was laid between Gallanach Bay, near [[Oban]], Scotland and [[Clarenville, Newfoundland and Labrador]], in Canada. It was inaugurated on September 25, 1956, initially carrying 36 telephone channels.

In the 1960s, transoceanic cables were [[coaxial cable]]s that transmitted [[frequency-division multiplexing|frequency-multiplexed voiceband signals]]. A high-voltage direct current on the inner conductor powered repeaters (two-way amplifiers placed at intervals along the cable). The first-generation repeaters remain among the most reliable [[vacuum tube]] amplifiers ever designed.<ref>{{cite web |url =http://www.iscpc.org/information/Timeline_History.htm |title =Learn About Submarine Cables |publisher =International Submarine Cable Protection Committee |url-status =dead |archive-url =https://web.archive.org/web/20071213042957/http://www.iscpc.org/information/Timeline_History.htm |archive-date =2007-12-13 |access-date =2007-12-30 }}. From this page: In 1966, after ten years of service, the 1,608 tubes in the repeaters had not suffered a single failure. In fact, after more than 100 million tube-hours over all, AT&T undersea repeaters were without failure.</ref> Later ones were transistorized. Many of these cables are still usable, but have been abandoned because their capacity is too small to be commercially viable. Some have been used as scientific instruments to measure earthquake waves and other geomagnetic events.<ref>{{cite web |url= http://www.whoi.edu/science/GG/DSO/H2O/EOSarticle/H2O_article_revised_9.pdf |title=The Hawaii-2 Observatory (H2O) |author=Butler, R. |author2 =A. D. Chave |author3= F. K. Duennebier |author4=D. R. Yoerger |author5=R. Petitt |author6=D. Harris |author7=F.B. Wooding |author8 =A. D. Bowen |author9=J. Bailey |author10=J. Jolly |author11=E. Hobart |author12=J. A. Hildebrand |author13=A. H. Dodeman |url-status= live |archive-url= https://web.archive.org/web/20080226234700/http://www.whoi.edu/science/GG/DSO/H2O/EOSarticle/H2O_article_revised_9.pdf |archive-date=2008-02-26}}</ref>