On September 25, 1956, TAT-1, the first submarine telephone cable across the Atlantic, was opened for service. It ran about 2,200 nautical miles from Gallanach Bay, near Oban in Scotland, to Clarenville in Newfoundland, with a branch to Nova Scotia. It had 36 voice channels and one television channel, and it was shared between Britain, the United States and Canada.
Radio was the only way. High-frequency radio links had carried transatlantic telephone calls since 1927, and they were subject to fading, interference and the state of the ionosphere, which meant that the number of circuits available went up and down with the sun. In 1956 the radio links could carry about 10 circuits at a time and the quality was poor enough that conversations were an event.
The repeater made it possible. A signal in a coaxial cable attenuates over distance, and amplifying it every few miles requires a device that will work for twenty years at the bottom of the ocean. The solution was a submarine repeater developed by Bell Labs, using vacuum tubes of extreme reliability and a cable design in which the armour and the conductor were arranged to survive being laid and being trawled. About 200 repeaters were spliced into TAT-1, roughly every 40 miles.
The cable was laid by the cable ship Monarch in two seasons, and it cost about 42 million dollars, split between AT&T, the British Post Office and the Canadian Overseas Telecommunication Corporation. The first call was made by the chairman of the Post Office and the president of AT&T, and by the end of the year about 50,000 calls had been made.
What followed was the rapid obsolescence of everything about it. TAT-1 was designed for 36 circuits and was carrying 48 by transistor improvements. TAT-2 opened in 1959, and by 1983 there were seven TAT cables plus satellites, and the capacity of the Atlantic was measured in thousands of circuits. Satellites took the long-distance traffic from 1965, and then fibre optics took it back from satellites: TAT-8 in 1988 was the first fibre cable and carried 40,000 circuits.
TAT-1 retired in 1978. The price of a three-minute call to New York had fallen from about 45 pounds in 1956 to a few pounds by the 1970s, and the transatlantic call had stopped being an event.