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.
Repeaters consist of such electronic devices as transistors.
Many telephone calls, especially long-distance calls, travel over coaxial cables. When used for telephone conversations, coaxials work in pairs. One coaxial carries signals in one direction, while the other handles signals from the other direction. A pair of coaxials may handle as many as 13,200 telephone conversations at once. Cable television systems use coaxial cables to transmit TV programs.