For example, a process called carrier transmission enables two pairs of wires to transmit as many as 96 telephone conversations simultaneously. Electronic filters at each end of the cable sort out the various conversations. Engineers have developed two kinds of cables that can carry especially large quantities of messages at once. Coaxial cables are made up of two conductors. The outer conductor is a rigid or flexible metal tube, and the inner conductor is a wire running through its center.
Insulation holds the wire in place.
A typical coaxial cable has about the same diameter as a pencil, and as many as 22 cables may be bundled together to make a larger cable. A coaxial cable's outer conductor shields the electric signals it carries from outside interference and helps prevent the signals from escaping. In addition, special amplifiers called repeaters are installed at various points along many coaxial cable systems to strengthen the signals. These amplifiers help prevent cable loss. Cable loss is the gradual weakening of signals as they travel along a cable.