![]() In pairs that are twisted, provided that the twist rate or pitch is greater than the wavelength of the interfering signal, the instantaneous signal in each of the conductors is still substantially equal. Accordingly, for this EMI suppression technique, all of the following are required: balanced transmission, differential signaling and twisted conductors. ![]() Even with balanced differential signaling, if the conductors are not twisted, the instantaneous interfering current in one conductor is stronger than in the other because most of the time they are not equidistant from the offending source. The resulting current flowing through them interferes with the intended analog or digital signal. ![]() Without balanced differential transmission a pair of wires passing through the oscillating field or noisy electromagnetic environment function as separate monopole antennae. Twisting a pair of conductors in the same circuit reduces the harmful effects of electromagnetic interference (EMI) due to proximity to one or more conductors carrying oscillating current or to a localized source of noise such as arcing brushes in a universal, dc or synchronous motor. Accordingly, these cable types are described as unshielded twisted pairs (UTP). Such bonding is highly effective in controlling electromagnetic interference, but Cat 5e and Cat 6a cable realize comparable protection by means of twisted conductor pairs. In contrast to coaxial cable, used in the first Ethernet installations, Cat 5e and 6a conductors are not surrounded by an outer metal shield grounded at both ends by connectors contacting the respective chassis. Cat 6a has higher bandwidth and is faster, but the less expensive Cat 5e is often chosen when adequate for the application. Cat 5e (enhanced) and 6a (augmented) are the most frequently-used media in residential and commercial Ethernet networks.
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