Contrast coaxial, twisted pair, fiber optic, and wireless network media. Coaxial cable has a center conductor that is wrapped in insulation that, in turn, is covered with a second conductor and wrapped again with a protective sheath. Coax offers high signal reliability in two ways. First, if the outer conductor is connected to earth ground, it shields the inner conductor from stray electromagnetic signals that may distort or cancel the desired signal. The fixed impedance allows the local area network to be designed with fixed distance and number of connections.
Twisted pair refers to the concentric twisting of two insulated conductors.
Twisted pairs are arranged so that an electrical signal and its return path share the twist. When bundled into larger cables, twisted pair conductors tend to induce excess electromagnetic impulses into the twist partner and not another twisted pair in the same cable. When an electromagnetic signal is imposed upon a twisted pair, the induced voltage is shared by the twist partners and thereby reduces signal distortion. The telephone company employs twisted pair wires throughout its network. Fiber optic cable employs light as the signal and is therefore immune to the effects of frequency-related impedance and electromagnetic interference that plagues copper conductors.