1956

TAT-1 Undersea Cable

By the 1950s, there was a powerful need to connect the United States and Europe with a reliable telephone line. Radio service did exist, but it was expensive and the quality was poor. A long wire was needed to connect the two sides of the Atlantic. By 1956, the technology to do it had become available and engineers assembled to create the TAT-1 (Transatlantic 1) undersea cable.

TAT-1 made use of several innovations. To cross the Atlantic—a distance of approximately 2,000 miles (3,200 km)—it used a pair of coaxial cables able to carry 36 simultaneous conversations. One coaxial cable carried the voices headed west to east, and the other carried those headed east to west.

When you see a coaxial cable for a TV in your home, it has a thin center conductor often made of copper, plastic insulation around it, a wire mesh shield, and then an outer protective cover. Undersea coax cables have the same kind of construction at their core, but with a more substantial center wire and shield. The TAT-1 cable was then wrapped in jute for padding, followed by an armored layer of heavy steel wires, more padding, and then an outer sheath.

Because of the distance, repeaters were spliced into the cable approximately every 40 miles (64 km). The repeaters received the signal, which had weakened over the course of the prior 40 miles, and amplified it so it could travel the next 40. TAT-1 used a line of vacuum tubes and other components sealed in Lucite to implement flexible repeaters that were spliced into the cable. Specially made high-reliability vacuum tubes with a rated life of 20 years formed the heart of the amplifiers. These tubes were burned in for 5,000 hours, inspected, and then certified for use in the cable.

Once the cable was installed, it remained in service for 22 years—a true testament to the quality of the engineering involved in its creation. Phone calls across the Atlantic were not inexpensive however. In 1956, a three-minute phone call cost $12, or roughly $100 in today’s dollars.

SEE ALSO Telephone (1876), Radio Station (1920), Smart Phone (2007).

This photo depicts the laying of the world’s first transatlantic telephone cable in Clarenville, Newfoundland. The project was the combined venture of the AT&T Long Lines department, American Telephone and Telegraph Company, and Canadian agencies.