© Mark Ollig
It would be the first underwater telephone cable to cross any ocean.
On Nov. 27, 1952, an agreement was made to install a deep-sea telephone cable across the Atlantic Ocean between the United States and the United Kingdom.
It was called the trans-Atlantic Telephone Cable System No. 1 (TAT-1).
TAT-1 was a joint venture of the American Telephone and Telegraph (AT&T) Long Lines Department, the Canadian Overseas Telecommunications Corporation, and the General Post Office of the United Kingdom (at that time, the government of England managed the post office and telephone services).
The TAT-1 would span 1,950 nautical miles across the North Atlantic Ocean, from Clarenville, Newfoundland, to Oban, Scotland.
The estimated construction cost of $42 million ($468 million today) would be divided, with Canada paying 10%, the United Kingdom 40%, and the US 50%.
It was agreed the only ship in the world capable of carrying and paying out the length of telephone cable needed to cross the Atlantic Ocean in a single operation was the 480-foot-long cable ship, Her Majesty’s Telegraph Ship (HMTS.) Monarch.
The HMTS Monarch, built in 1945, had four sizable cylindrical container drums that could hold the miles of coiled telephone cable needed to cross the Atlantic.
The TAT-1 system consisted of two cables, one for telephone calls transmitted from west to east and another for calls traveling east to west.
The HMTS Monarch laid the west-to-east telephone cable across the ocean during the summer of 1955 and the east-to-west the following year.
The parallel-running trans-Atlantic telephone cables were spaced 20 miles apart.
The newly designed and manufactured 1.25-inch diameter trans-Atlantic telephone coaxial cable contained a solid copper conductor wire at its core. A thick, damage-resistant polyethylene plastic insulation was molded over the copper conductor.
The layering of shielding materials protecting the copper conductor included sturdy cloth fabric, heavy armor-wire tapes, steel armor wire, polyethylene insulation, and strong threaded jute fiber wrapped around the cable. In addition, a galvanized coating of the metals would prevent any corrosion.
The trans-Atlantic telephone cable was constructed to survive the depths, hazards, and elements of the Atlantic Ocean.
Western Electric, a subsidiary of AT&T, manufactured the high-gain amplifying repeaters critical for boosting voice signals through the telephone cables crossing the Atlantic.
British-made repeaters were used in the shallower waters between Nova Scotia and Newfoundland.
North Electric Company, a telecommunications manufacturer in Ottawa, Canada, also provided equipment.
Onshore power stations supplied regulated 2,000 volts of direct current into both trans-Atlantic cables, with negative and positive potentials totaling 4,000 volts.
This voltage powered the 52 eight-foot-long, three-inch diameter repeaters enclosed in flexible copper tube watertight metal casings attached in series to each cable crossing the Atlantic.
These repeaters contained long-life, high-gain vacuum tubes, and other electronic components.
One hundred four repeaters were connected to both cables every 43 miles along the route crossing the Atlantic Ocean, with 14 repeaters connected to the TAT-1 onshore cables.
The cable repeaters generated 65 dB of audio gain, ensuring clear and continuous voice transmission instead of the sometimes inconsistent voice audio quality experienced using the trans-Atlantic over-the-air radiotelephone system.
Each repeater amplified its incoming audio electrical signal, then passed it along to the next repeater, which replicated amplification.
Individual repeater units are fitted in acrylic cylinders enclosed by overlapping steel rings and copper tube casing. Both ends of a repeater’s enclosure are watertight and tapered to the same diameter as the trans-Atlantic cable.
The cable repeaters had a 20-year life expectancy.
The ocean depth at times reached 2.5 miles, where 6,000 pounds of pressure per square inch surrounded the telephone cable and repeaters.
The TAT-1 initial bandwidth capacity provided 36 two-way voice channels. Later, this increased to 48 and finally to 51.
In the summer of 1956, the final splices of the trans-Atlantic telephone cable were made in Newfoundland, Canada, to Portland, ME, where onshore cables physically connected with AT&T’s Bell Telephone System network.
On Sept. 25, 1956, a seven-minute three-way telephone conversation took place between TAT-1 officials in New York, London, and Ottawa, Canada.
“I now declare the cable open for service between the United States and the United Kingdom,” said Cleo F. Craig, Chairman of the Board of AT&T, from New York.
You can listen to this historic telephone call at https://bit.ly/3GO4uWH.
On Sept. 26, 1956, The Minneapolis Morning Tribune reported media representatives met on the 13th floor of the Northwestern Bell Telephone Building (now Lumen Technologies) on 224 S 5th St. in Minneapolis.
They and Northwestern Bell officials talked on a telephone with Albert J. Semkens, senior telecommunications superintendent in London, using the new trans-Atlantic telephone 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.
The trans-Atlantic telephone cable handled 588 telephone calls on the first day it became available to the public.
In 1978, TAT-1 was retired, and its telephone traffic was transferred to other trans-Atlantic cables.
In December of 1988, the first fiber-optic trans-Atlantic cable, TAT-8, was placed into service with the capacity to handle 40,000 simultaneous telephone calls.
