Cables are made up of conductors that transmit electricity surrounded by insulation. Common cable types include fiber optic cables which transmit data using light through glass or plastic fibers, coaxial cables with a copper conductor surrounded by insulating material and a shield, and twisted pair cables which rely on twisting copper wires to reduce interference. Cable components must have appropriate electrical, mechanical, and chemical properties to safely and reliably transmit signals or power. Common conductor materials include copper, aluminum, and alloy-coated steel wires.