For some reason, communications and power infrastructure fascinates me, especially the long-haul lines that move power and data over huge distances. There’s something about the scale of these projects that really gets to me, whether it’s a high-tension line marching across the countryside or a cell tower on some remote mountain peak. I recently wrote about infrastructure with a field guide that outlines some of the equipment you can spot on utility poles. But the poles and wires all have to end at the shore. Naturally we have to wonder about the history of the utilities you can’t see – the ones that run under the sea.

Cyrus Field’s Folly

We tend to forget how isolated the world was in the 19th century. The invention and commercialization of telegraphy in the middle of the century lead to a rapid build-out of the lines and circuits needed to connect cities and towns across the world. People rapidly got used to communicating at the speed of light, but since the telegraph system was limited by wires strung on poles, the speed of communication across the ocean quickly dropped to the speed of the fastest ship.

Telegraph companies and bold entrepreneurs began dreaming of undersea telegraph lines, and even managed to lay a few across narrow bodies of water by the 1850s. But the dream of connecting Europe and America seemed too audacious, at least until Cyrus West Field came along. A self-made man and one of the richest in New York, Field was retired by his 30s and sitting on a load of capital. He decided to throw his resources into a transatlantic cable that would run on the Great Circle Route from Newfoundland to Ireland, with existing submarine cables completing the link from England to the United States.

These efforts were met by a series of disasters. The first cable snapped after only a few miles had been laid due to a nervous engineer who slammed on the laying gear brakes. With multiple expeditions over a four-year period, a cable was completed in 1858. The event was greeted by raucous celebrations by jubilant crowds on both sides of the ocean. Queen Victoria and President Buchanan exchanged ceremonial greetings over the line, but it must have been a boring conversation – line quality issues limited bandwidth severely enough to make the 96-word message take hours to transmit. Quality rapidly degraded, and soon a single word would take an hour to come across. Within a month, the line went dead completely, thanks to the efforts of one Wildman Whitehouse, chief electrician for the cable. He applied 2000 volts to cable and ruined it.

Subsequent cables were laid, some by Field’s company and some by others. Advances in cable design, and better hires in the engineering department, lead to greater durability, better bandwidth, and multiple circuits in the same cable. Eventually the technology advanced to multiplex telegraphy, and by the late 1870s a sophisticated web of lines connecting the Old World and the New World hummed with traffic. The hemispheres have been connected ever since.

TAT-1: Can you hear me now?

Despite the advances in cable-laying technology during this period, and even though the telephone came into use by the late 1870s, it wouldn’t be until 1956 that the first transatlantic telephone system, TAT-1, was brought online. From our point of view, it might seem odd that it took almost a century to go from telegraphy to telephony, but piping a phone call through 2800 km of wire is quite a bit more technically challenging than clicking a telegraph sounder. It would take the technological developments of a pair of world wars and the rise of the radio industry to provide the essential pieces of equipment: coaxial cable and inline repeaters.

The early submarine telegraph cables were simple in design: copper conductors insulated and waterproofed with natural materials like hemp rope and gutta percha, and armored with steel wire. But telephone calls require more bandwidth than telegraphy, and simple parallel conductors, especially ones surrounded by a conductive medium like seawater, are not good at the higher frequencies needed for higher bandwidth. Developments in coax allowed more signals to be packed onto a single line, and made the cable financially feasible.

The TAT-1 system would have two cables, one for east-west traffic, the other for west-east calls. The core of each cable was a single coaxial cable with a solid copper center conductor, polyethylene dielectric, and multiple shields of copper tape. The shield not only provided a return path for the signal but also protected the cable from marine worms. The whole cable was wrapped in cloth tape and jute impregnated with waterproofing and wrapped in steel wires for armoring. Heavier armor was used on the 500 km sections closest to each shore, where damage from anchors and trawling nets was more likely.

The coaxial cable alone wasn’t enough to propagate the signals across the Atlantic, though. The cable design for TAT-1 included flexible inline repeaters to boost the signal at 69 km intervals. Each of the 2.5 meter long repeaters used three vacuum tubes, specially ruggedized and built to withstand the pressure 8000 meters under the sea. The repeaters provided 65 dB of gain and a 144 kHz bandwidth. Vacuum tubes were used despite the fact that the repeaters were designed by Bell Labs, which had only recently invented the transistor; it was felt that transistors weren’t proven technology like vacuum tubes. That would turn out to be the right call – not a single one of the hundred plus tubes failed during the 22 years TAT-1 was in service.

The Hotline

When TAT-1 went into service in September of 1956 it provided 36 channels – 35 phone channels with 4 kHz of bandwidth, with 22 telegraph circuits on the 36th channel. Improvements in carrier technology and narrowing the bandwidth to 3 kHz eventually brought the cable up to 51 channels. In 1963 the hotline between Moscow and Washington went into service over TAT-1 using a teleprinter (the fabled “red phone” is a farce, this was never a voice line). TAT-1 stayed in service until 1978, and the success of the system led to a long line of TAT cables. All the TAT cables have been retired except for TAT-14, a fiber optic cable designed to carry 9.38 Tb/s that went into service in 2001. It’s worth noting that the US government lists TAT-14’s landing point in the Netherlands as a critical infrastructure target for terrorists.

Since the first transatlantic cables were laid, hundreds of others have joined them, crossing almost ever ocean and joining every continent except Antarctica. These cables tie the world together in a way the early pioneers couldn’t imagine, but which their successes and failures made possible.