This film follows the laying of a cable from Jacksonville, Florida, to St. Thomas in the Virgin Islands. The C.S. Long Lines makes a journey of 1302 nautical miles.
The cable AT&T Long Lines used, of the copper coaxial type (fiber optics wouldn't come into play until the late 1980s), was the very first undersea cable to use transistors in the repeaters, instead of vacuum tubes. This was 21 years after the invention of the transistor.
This cable carried 845 channels, and was 1/10th of the cost of the very first undersea telephone cable, laid in 1956.
You can see pictures of the cable's landfall, taken by a transmission engineer on the journey, at the Atlantic Cable site.
More importantly, this was the first journey documenting AT&T's use of their newly-developed sea plow, which had been first tested in 1967. In the Atlantic/Caribbean regions, undersea cables were frequently severed after being snagged by fishing trawlers. The sea plow, burying the cable, drastically reduced those expensive incidents. The plow, pulled by the cable-laying ship on sled-like runners, could bury cable on the ocean floor under water up to 4600 feet deep.
This particular cable was taken out of service in 1993. As of 2011, three cables run to the same terminus in St. Thomas, all fiber optic, and all put into service that same year, 1993.
A Jerry Fairbanks Production
Written by Robert Hecker
Directed by Wallace Bennett
Footage courtesy of AT&T Archives and History Center, Warren, NJ