An underwater communications cable is a cable placed on the seabed between ground stations to carry telecommunications signals across ocean sections. The first submarine communications cables, installed in the 1850s, carried telegraph traffic. Subsequent generations of cables carried the telephone traffic and then the traffic of data communications. Modern cables use fiber optic technology to carry digital data, including telephone, Internet and private data traffic.
Modern cables have a diameter of about 1 inch (25 mm) and weigh about 2.5 tonnes per mile (1.4 tonnes per km) for the deep water sections that make up most of the run, although they are used larger and heavier cables, sections of water near the coast. Submarine cables connected all continents of the world except Antarctica when Java was connected to Darwin, Northern Territory, Australia in 1871 in anticipation of the termination of the Australian land telegraph line in 1872 connecting Adelaide, South Australia and the rest from Australia.