Cover of the issue of the Bell System Technical Journal Containing the paper on route selection and cable laying for the Transatlantic Cable
Image Source: archive.org
Detail map of Oban, Scotland, United Kingdom,Clarenville, Newfoundland and Labrador, Canada

A: Oban, Scotland, United Kingdom, B: Clarenville, Newfoundland and Labrador, Canada

The First Transatlantic Telephone Cable is Operational

1955 to 9/25/1956
Transatlantic telephone cable routes under study in early 1956.
Image Source: en.wikipedia.org

Transatlantic telephone cable routes under study in early 1956. American Telephone and Telegraph Company. From J. S. Jac, W. H. Leech, & H. A. Lewis, "Route Selection and Cable Laying for the Transatlantic Cable System," Bell System Technical Journal , l (1957) No. 1, 296.

On September 25, 1956 the first transatlantic telephone cable, TAT-1, became operational, carrying 36 telephone channels. It was laid between Gallanach Bay, near Oban, Scotland and Clarenville, Newfoundland between 1955 and 1956. 

Prior to this development, since 1927, very expensive radio-based transatlantic telephone service was available. However, radio-based transatlantic telephone service carried only around 2000 calls per year.

Timeline Themes

Telecommunications
Telephone / Videotelephony
Radio
Internet & Networking