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TAT-1 was the first transatlantic cable to connect the United Kingdom with the United States of America and Canada. The cable remained in service from September 25, 1956, until 1978.

Earlier telegraph cables had been laid during the 19th century (such as those by Captain James Anderson), but this was the first transatlantic cable capable of carrying voice communications.

In the first day of public service, there were 588 calls from London to the United States and 119 to Canada. During the first year of operation the telephone cable carried twice the calls made by radiotelephone.

It trebled the number of calls that could be made across the Atlantic, and initially allowed 36 simultaneous transatlantic conversations using 4 kHz channels, later increased to 48 by reducing the bandwidth to 3 kHz. In its first year of service, the new link carried almost 300,000 calls at a cost of £3 for three minutes. Previous calls had to be made using radio links which, at the time, were far less reliable. Notably, as well as the voice circuits, the cable also provided the famous "Hot Line" of the Cold War, which allowed private conversations to take place between the world's leaders.

The project took three years to complete and cost more than £12.5 million, and was a joint initiative undertaken by the American Telegraph and Telephone Company (AT&T), the Post Office Engineering Department (GPO), Canadian Overseas Telecommunications Corporation, who owned 50%, 41%, and 9% of the cable respectively, and Bell Telephone Laboratories.

Bell Telephone Laboratories developed the main subsea link which consisted of two armoured cables, one for each direction, using technology developed during and after World War II to help place the cable and booster stations on the sea bed two miles under the ocean. AT&T developed a deep water system, and this system was used for the new link. Submarine Cables Ltd was involved in the manufacture of many of the new co-axial telephone cables after the war, and manufactured 92% of the 3,884 nautical miles of cable required for the project.

Her Majesty's Telegraph Ship (HMTS) Monarch, a cableship built by the Post Office in 1945, was used to lay the 2,240 mile cable which ran from Gallanach Bay, along the Sound of Kerrera near Oban in Argyll and Bute, to Clarenville, Newfoundland, Canada. At the time, this was was the only existing cableship capable of conveying the 1,500 nautical miles of cable, which had to be laid in one piece across the deepest part of the Atlantic. The cableship could not approach the shallow waters of Gallannach Bay, and the Oban shore ends of TAT-1 were laid by Glenaray, a Clyde puffer believed to have been VIC 89.

The new TAT-1 cable had to be laid in three sections. The east and west ends were thicker cable designed to withstand the rougher treatment expected in shallow water. The Monarch, under Captain JPF Betson, left Clarenville on July 22, 1955, bound for Oban, laying the first cable along the floor of the Atlantic Ocean for a distance of 2,250 miles (3,621 km). The following year a return cable was laid from Oban to Clarenville. The cable was extended overland to Terrenceville, then on to Sydney Mines, Nova Scotia in 1956. The cable had repeaters installed at regular intervals, with 51 repeaters in each cable, 102 repeaters in all, powered from Oban and Clarenville. In terms of reliable operation, the most critical component of the system was the repeater. Spaced at intervals of 37.5 nautical miles along the cable, the repeaters compensated for signal loss. The repeaters were of a unique flexible design, which allowed them to be handled in the same manner as cable. Standard technology up to that point had used a rigid repeater, which would have required a new design of ship for deep ocean laying, and estimates of traffic, which later proved to be far too conservative, did not justify the required expenditure. The new repeater still used old technology, transistors had only been invented in 1947 and were still developmental, and one of the key elements within each repeater was a set of three vacuum valves. It was unprecedented to place such components two and a half miles below the ocean's surface and expect them to operate without failure over a period of years. One of the key causes of valve failure was impurities contained in the materials they were manufactured from, a problem aggravated by the fact that the valves contained a heater which boiled electrons off the cathode, leading to accelerated oxidisation and reduction effects within the valve. In order to reduce this effect, extensive material testing was carried out to select the purest batch of material from which to manufacture the valves used in the transatlantic cable's repeaters. In fact, the vacuum valves of TAT-1 never failed in more than twenty years of continuous operation.[1]

On September 25, 1956, at 11 am EST, the first inaugural call took place in a conversation between the British Postmaster General at a ceremony held at Lancaster House in London, the chairman of AT&T in New York, and the Canadian Minister of Transport.

A section of the cable is on display at the Communicate! gallery of the Royal Museum, Edinburgh.


The Clarenville cable station was built on what is now known as Cormack Drive, and was managed by the Eastern Telephone and Telegraph Company, a subsidiary or AT&T. A booster station, Clarenville's primary responsibility was to supply power to half the cable, and the ground floor of the building was almost entirely devoted to the production of electricity. It housed four large diesel generators, two of which powered the cable while two were held in reserve. The basement housed 132 batteries, which would automatically supply power to the cable in the event of a power outage, and maintain operation until the generators could be brought on line. The communication equipment was installed on the first floor.

The station also played an important role in the repair of cable breaks. By measuring the resistance on the line, employees in the station could determine the location of the break, and pass the position to the cable repair ship, based in St John's.

Even though all telephone conversations between North America and Europe passed through the station, the design of the transatlantic system meant that long distance calls between Clarenville and Europe had to be routed via Montreal.

Clarenville memorial

The town of Clarenville, erected a monument next to the old cable station on Cormack Drive. Erected in the summer of 2005, the monument contains 2 plaques: one commemorates the 50th anniversary of the landing of TAT-1, the first transatlantic telephone cable, on June 28, 1955; the second was erected by the Institute of Electrical and Electronics Engineers (IEEE) for a milestone in Electrical Engineering and Computing, for the first submarine transatlantic telephone cable system in 1956.

Oban Radio GNE

Oban Radio was established in 1949 in response to pressure from the fishing industry for better coverage of Scotland's northwest coastline. The station had the callsign GNE, and remained in operation until 1982. Originally sited at the south end of the former RAF Connel airfield, the station moved about one mile to east, into a former RAF accommodation camp about one mile to the east.

The following account of the station's involvement in the laying of TAT-1 not noted elsewhere, was discovered in short article on a site devoted to the station:

For the construction of the first transatlantic telephone cable (TAT-1), which came ashore at Gallanach Bay near Oban, it was vitally important that communication could be maintained 24 hours a day between the cable ship laying the cable, the cable station at Gallanach and the remote cable head at St. Johns, Newfoundland. This was achieved by fitting Oban Radio out with a vast range communications equipment, including facilites (sic) for WT on the 500kHz band (the only time the station was heard on this band), WT and RT on HF (short wave) and also radio teleprinter facilites, something which did not become common in the shipping world until many years later.

As well as this advanced communications system, the facility was also provided to remote-control the equipment from the Gallanach Cable Station - a very advanced feature for the day! During the day, for the duration of the laying of this cable, a Radio Officer would attend at Gallanach to provide the cable head with their communication to the ship. In the evening control reverted to the radio station.

On satisfactory completion of the cable these advanced facilities were closed down and subsequently removed from the station.

- Oban Radio, long range communications.[2]


1 Reminiscences of TAT-1, Jeremiah F Hayes, Concordia University, Montreal.

2 Oban Radio, long range communications.

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