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

1963 TAT-3

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

A Proposed New Cable System Direct to U.S.A.—TAT-3

On 20 July 1960 an agreement was signed between the Postmaster-General and the American Telephone and Telegraph Company (AT&T Co.) for the provision of a repeatered submarine cable to run directly between Great Britain and the United States. The system is to be completed as early as possible in 1963 and will provide 128 3 kc/s-spaced telephone circuits, or their equivalent, on a single coaxial cable some 3,400 nautical miles (n.m.) long.

Existing and projected telephone cable systems across the Atlantic include:

( a ) TAT-1: two unidirectional cables, Scotland­Newfoundland, of 1,950 n.m., provided 36 4 kc/s­spaced circuits initially and subsequently increased by the use of 3 kc/s-spacing and T.A.S.I. 2 (1956).

(b) TAT-2: as TAT-1, but between Brittany and Newfoundland (1958).

(c) CANTAT: single cable, Scotland-Newfoundland, of 2,000 n.m., providing 60 4 kc/s-spaced circuits initially and then 80 3 kc/s-spaced circuits (1961).

(d) SCOTICE/ICECAN4: single cable, Scotland­Iceland-Greenland-Newfoundland, providing 24 3 kc/s­spaced circuits initially (1962).

The new project, TAT-3, which is estimated to cost about £12 million, will be undertaken by the Post Office and AT&T Co. in equal partnership. The system will employ light-weight (armourless) cable and two-way rigid repeaters of American design, representing the results of intensive development by the Bell Telephone Laboratories of the type of system being used by Great Britain and the Commonwealth Partners in the CANTAT and Commonwealth Pacific (COMPAC) cables.

The cable will have a core diameter of 1 in. and will differ from the CANTAT cable in important details, including the use of a single longitudinal copper tape as a return conductor. This gives a more nearly ideal structure than multiple helical tapes and should tend to be more stable. It is, however, much more liable to damage due to repeated bending and, in consequence, is to be laid by caterpillar gear instead of a rotating cable drum; the caterpillar tracks can distort sufficiently to “swallow” the rigid repeaters.

The system is designed for up to 180 repeaters at a spacing of about 20 n.m. and, to maintain a direct current of 0·43 amp through the system, a terminal voltage of about 6 kV will be required at each end.

The terminal points of the system have not yet been decided. In view of the number of breaks which have occurred in TAT-1 and TAT-2 due to the activities of heavy trawlers, mainly off Newfoundland, very careful consideration will be given to the routing of the shallow­water sections of the cable and to means for their greater protection against damage.

Telephone traffic between Great Britain and the United States is already three-and-a-half times greater than it was before TAT-1 opened in 1956, and is growing at the rate of about 500 calls per month. To begin with, some of the circuits in TAT-3 will be used for telephone calls between the United States and Europe and, so, will provide relief for both TAT-1 and TAT-2.

R. J. H[alsey]

References

1. The Transatlantic Telephone Cable. P.0.E.E.J., Vol. 49, Part 4, Jan. 1957.

2. HALSEY, R. J. The Economic Usage of Broadband Transmission Systems. P.0.E.E.J., Vol. 51, p. 212, Oct. 1958.

3. A Proposed New Telephone Cable between the United Kingdom and Canada. P.0.E.E.J., Vol. 50, p. 104, July 1957.

4. The SCOTICE/ICECAN Submarine Cable Projects. P.O.E.E.J., Vol. 53, p. 56, Apr. 1960.

5. BROCKBANK, R. A., and MEYERS, A. L. A New Deep-Sea Coaxial Cable. P.O.E.E.J., Vol. 50, p. 7, Apr. 1957.

6. Proposed Commonwealth Pacific Telephone Cable System. P.O.E.E.J., Vol. 53, p. 42, Apr. 1960.

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