A Coaxial cable is a special electrical cable. It is used to transmit signals. The cable is specially insulated. This makes it quite stiff. Today, coaxial cables are used for things like Cable TV. Coaxial cables can also be used for computer networks, but this became rare in the 21st century, as twisted pair cables can be used more easily.
Such cables are usually made of a conducting wire. Then there is some insulation, then there is another layer of conducting material. Finally there is the (insulating) mantle. Such cables are used as a high-frequency transmission line to carry a high-frequency or broadband signal. Because the electromagnetic field carrying the signal exists (ideally) only in the space between the inner and outer conductors, it cannot interfere with or suffer interference from external electromagnetic fields.
There are different types of coaxial cables, which satisfy different standards.
1936 — World's first underwater coaxial cable installed between Apollo Bay, near Melbourne, Australia, and Stanley, Tasmania. The 300 km cable can carry one 8.5-kHz broadcast channel and seven telephone channels.[5]
1936 — AT&T installs experimental coaxial telephone and television cable between New York and Philadelphia, with automatic booster stations every ten miles. Completed in December, it can transmit 240 telephone calls simultaneously.[6][7]
1941 — First commercial use in USA by AT&T, between Minneapolis, Minnesota and Stevens Point, Wisconsin. L1 system with capacity of one TV channel or 480 telephone circuits.
1956 — First transatlantic coaxial cable laid, TAT-1.[10][11]
