@MarkOllig
The project to install the Transatlantic Telephone Cable System No. 1 (TAT-1) was officially announced Dec. 1, 1953.
Earl De La Warr, Britain’s postmaster general, hailed the installation of this transatlantic cable as “the beginning of a new chapter in the history of communications.”
It would be the first submarine telephone cable to cross the Atlantic Ocean, linking the United States and the United Kingdom.
Before TAT-1, transatlantic calls relied on a 12-circuit radiotelephone system that was frequently disrupted by atmospheric conditions; TAT-1 would provide a more stable service and triple the capacity to 36 circuits.
The TAT-1 project was a collaboration between American Telephone and Telegraph Co., the Canadian Overseas Telecommunications Corp., and the UK’s British Post Office, which was also the United Kingdom’s telecommunications carrier.
The $42 million construction cost (about $506 million today) was split: Canada paid 10%, the UK provided 40%, and the US covered 50%.
In 1953, Her Majesty’s Telegraph Ship (HMTS) Monarch, a British 480-foot cable vessel, was recognized as the “world’s largest cable ship.”
The HMTS Monarch played a vital role in the TAT-1 cable project by transporting the large spools of coaxial cables in its four cable tanks.
Each TAT-1 cable consisted of three parts: two armored shallow-water sections and a continuous central section of about 2,244 statute (land) miles that crossed the North Atlantic Ocean from Gallanach Bay, near Oban, Scotland, to Clarenville, Newfoundland.
From Clarenville, a separate coaxial submarine telephone cable crossed the Cabot Strait to Sydney Mines, Nova Scotia; this extension was 271 nautical miles long (nautical is a unit of distance used in sea navigation).
From Sydney Mines, microwave radio relay and landline circuits carried the communications onward to Portland, ME, and then to New York, NY, via the US Public Switched Telephone Network.
The HMTS Monarch laid the cable between Oban, Scotland, and Clarenville, Newfoundland, during the summers of 1955 and 1956.
The TAT-1 deep-sea system had two 1.625-inch coaxial cables spaced about 20 miles apart for bidirectional communication: one for west-to-east and the other for east-to-west traffic.
Each cable had a solid copper core, thick polyethylene insulation, and reinforced steel armor-wire tapes for strength and corrosion protection.
It was laid at an average depth of 2.5 miles in the ocean, withstanding 6,000 pounds of pressure per square inch.
The cables included repeaters (boosters) placed at different intervals to amplify the signal across the Atlantic.
In deep-sea sections, repeaters were spaced 37.5 nautical miles apart, while in shallow waters, they were about 20 nautical miles apart.
Western Electric, a subsidiary of AT&T, produced eight-foot-long repeaters that boosted audio signals using high-gain vacuum tubes to achieve a 65dB audio gain.
The repeaters were contained in watertight casings made of overlapping steel rings and copper tubes, designed to withstand deep-sea pressure.
Each repeater had a lifespan of 20 years and operated on about 4,000 volts of direct current (DC).
Power was supplied from shore stations in Clarenville, Newfoundland, and Labrador, and Oban, Scotland, minimizing electrical losses over the 2,240-mile distance.
DC power was delivered through the central conductor of the coaxial cable, necessitating that the repeaters be wired in series.
Each repeater contained Western Electric 175HQ vacuum tubes, which were assembled in extremely clean conditions comparable to those used in early semiconductor manufacturing to ensure their longevity.
The reliable operation of the TAT-1 repeater system resulted from the high quality of the vacuum tubes and gas tubes designed to bypass faulty component stages in the event of a failure.
TAT-1 offered 36 circuits in total. Of these, 35 were for two-way voice telecommunications – 29 connecting New York and London, and six connecting Montreal and London.
The 36th circuit was used for telegraph services.
TAT-1 was completed in July 1956, with the final cable splices being made in Newfoundland.
A seven-minute, three-way telephone call took place between officials in New York, London, and Ottawa, Canada, Sept. 25, 1956.
“I now declare the cable open for service between the United States and the United Kingdom,” said AT&T chairman Cleo F. Craig in New York.
A recording of this historic call can be heard at .
In its first 24 hours of public service, TAT-1 carried 588 calls between London and the United States and 119 between London and Canada.
A three-minute call between Minneapolis and London was priced at $12 ($141 today) on weekdays and $9 ($106 today) on Sundays (plus tax, of course).
The Minneapolis Morning Tribune reported that media representatives met with Northwestern Bell (now Lumen Technologies) officials at 224 S. Fifth St. in Minneapolis Sept. 26, 1956.
They spoke with Albert J. Semkens, a senior telecommunications superintendent in London, over the new transatlantic cable.
“We are in Lancaster House, in the heart of historic London,” Semkens said.
“Transmission seems to be very good. I can hear every inflection in your voice,” a Northwestern Bell official replied.
In 1960, the TAT-1 cable’s capacity was upgraded to 72 audio circuits.
TAT-1 began carrying the circuit for the Moscow-Washington “hotline” Aug. 30, 1963.
In 1978, TAT-1 was retired, and its telephone traffic transferred to higher-capacity cables that had been installed across the Atlantic, such as TAT-6 and TAT-7.
