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History of the Atlantic Cable & Undersea Communications
from the first submarine cable of 1850 to the worldwide fiber optic network

1960 Anglo-Swedish Cable

The Post Office Electrical Engineers’ Journal
Vol. 53 Part 3. October 1960

The Anglo-Swedish Submarine Telephone Cable

The laying of the first direct submarine telephone cable between the United Kingdom and Sweden was completed on 17 June [1960].

The new cable is the longest submarine cable in the world equipped with submerged repeaters for two-way operation and is a joint project by the United Kingdom Post Office and the Royal Board of Swedish Telecommunications. The cable, repeaters and terminal equipment are of British design and manufacture and will provide 60 telephone circuits of C.C.I.T.T. quality.

At the United Kingdom end the terminal equipment is installed in a new repeater station at Middlesbrough; in Sweden the terminal equipment is at Goteborg. The submarine cable route is from Marske, about 10 miles east of Middlesbrough, to Sandvik, some 10 miles from Goteborg. The submarine section is about 510 nautical miles (n.m.) long and the length of the whole system between the terminal stations at Middlesbrough and Goteborg is about 527 n.m.

The terminal equipment assembles the 60 circuits from five basic 12-circuit carrier groups (60-l08 kc/s) into the frequency bands 60-300 kc/s for transmission in the Goteborg-Middlesbrough direction and 360-608 kc/s for the reverse direction. The 360-608 kc/s band includes an 8 kc/s portion used in the repeater monitoring system.

From Middlesbrough the circuits in the new cable are extended to London in carrier and coaxial cables while from Goteborg the circuits are extended to Stockholm by coaxial cable. London-Stockholm 12-circuit groups are provided in this way without the necessity for translation to audio frequency at intermediate points.

The cable is fitted with 29 submerged repeaters of the latest British design. This type of repeater has been developed for use on the United Kingdom-Canada cable (CANTAT) to be laid in 1961, which will be the first link in the Commonwealth “round-the-world” telephone cable system. The same design of repeater will also be used on the Commonwealth Pacific cable from Canada to New Zealand and Australia, the next link in the Commonwealth cable system. Notable features of the repeaters are the use of new and improved long-life valves, which have enabled the repeater operating voltage to be reduced, and a new monitoring unit with which it is possible to locate not only all the usual types of fault but also, for the first time in a British repeater, a wideband noise fault.

A nest of repeaters on the deck of the cable ship Monarch, 8,056 tons, during the laying recently of a new submarine telephone cable between Middlesbrough and Gottenburg, Sweden. In all, 29 repeaters were spliced into the cable to maintain the speech signal strengths in its 60 telephone circuits.

The repeater characteristics have been designed to meet the requirements for the new British light-weight armourless cable to be used for the deep-water sections of the Commonwealth system. The cable on the United Kingdom-Sweden route is, however, conventionally armoured to provide the mechanical protection needed for a shallow­water route, but the internal construction of the cable has been modified so that its impedance and loss/frequency characteristics are similar to those of light­weight cable. This simulation of the characteristics of light-weight cable has been achieved by the use of a composite centre conductor comprising a core of stranded­steel wires surrounded by an outer longitudinal copper tape. This tape is formed into a tube around the stranded core by means of a seam joint similar to that used for metal boxes. Conventional polythene-dielectric insulation with an outer diameter of 0·62 in. is used and the outer conductor consists of six helical copper tapes with an overlapped copper binding tape. Most of the cable is armoured with No. 2 S.W.G. mild-steel wires, but about 100 n.m. in deeper water is armoured with No. 6 S.W.G. mild-steel wires.

Power-feeding equipment maintains a constant direct current to the cable, regulated to within ± 1 per cent, to energize the repeaters. Since the cable is short relative to the design capabilities of the system, the whole of the power is fed from the Middlesbrough terminal, the total line voltage being about 3,500 volts.

The Post Office cable ship Monarch laid some 490 n.m. of the main cable, including 28 submerged repeaters, between 10 June and 15 June. Shore ends at Marske and Sandvik had been laid in advance by the smaller Post Office cable ship Ariel. The cable was completed by Ariel laying some 16 n.m. of cable, including the 29th repeater, in shallow water at the Swedish end of the route and making the final splice on 17 June.

The new cable is another link in the extensive network of submarine cables between the United Kingdom and the Continent. It will provide a valuable direct route to meet the ever increasing demands for telephone and telegraph facilities between this country and Sweden, and neighbouring countries.


Last revised: 19 January, 2022

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