Anglo-Canadian transatlantic telephone cable (CANTAT). Planning and overall performance

When the first transatlantic telephone cable was planned in 1953 there were two possible systems available: one American, using small-diameter flexible repeaters in two uni-directional cables, and the other British, using much larger, rigid repeaters in a single cable. The former was the more advanced, particularly with respect to laying methods in ocean depths, and was adopted for the main Atlantic crossing, the British system being used between Newfoundland and Nova Scotia. As early as 1951, the British Post Office had started development of a revolutionary type of coaxial cable for use in deep water. This had its strength member in the centre, torsionally balanced, and an external sheath of polythene; its non-twisting characteristics under tension promised major improvements in laying and recovery techniques. When, in 1957, the British and Canadian Governments agreed to provide a new submarine telephone cable between the two countries, British rigid repeaters with the new British Lightweight cable in deep water were envisaged. This cable system, known as CANTAT, was developed, manufactured and completed within a period of four years. In addition to overland connections in Great Britain and Canada to London and Montreal, respectively, there are two submarine cable links, one between Scotland and Newfoundland, providing 240 kc/s bandwidth in each direction (initially 60 telephone circuits recently increased to 80), and one in the Gulf of St. Lawrence providing 480kc/s bandwidth in each direction (initially 120 telephone circuits capable of increase to 160). The system was opened for service by Her Majesty The Queen in December 1961, and is, for the present, the most advanced installation of its kind.