A twisted pair is a set of two conductors tightly wrapped together in a series of twists to minimize interference and allow them to transmit a signal as clearly as possible. This wiring is useful for telecommunications equipment like phones and cable lines to prevent crosstalk and other issues that might interfere with the quality of the signal. There are a number of types of twisted pair wiring available for use in different applications, each with a rating to provide information about the kinds of settings where it can be used.
When two conductors run side by side, each generates its own electromagnetic field as energy moves through. Occasionally, artificial connections can develop between the wires, and may create crosstalk, where signals jump between wires. This can create a compounding effect over long distances. Twisting limits exposure to interference by continually switching which wire is exposed to a neighbor. Technicians do need to be careful with the wiring, as they could accidentally create a switched pair at the end, where two wires from two different pairs are joined together at a junction or connection box.
Manufacturers can introduce differing numbers of twists into the wire. More twists creates more of a canceling effect to limit interference, but also adds to the cost of the wire. The manufacturer needs to balance the needs of the applications where the wire will be used against the expenses associated with production. Typically multiple twisted pairs are run together in a single cable. The twist rate of each pair varies, as identical twisted pairs yoked together can start to interfere with each other.
The most basic twisted pair is unshielded, where individual conductors wrapped in basic sheaths are twisted around each other and bundled in the same cable. In shielded twisted pair wiring, the manufacturer wraps the pairs in foil and adds insulation. This limits communication between pairs, and may be recommended for things like high speed data transmission. Without shielding, interference could occur and might degrade the signal.
Ratings for twisted pair wiring are based on the number of twists and the type of insulation. High twist, high insulation wire is rated for demanding applications like high-speed Internet. Low levels of twist and low insulation are suitable primarily for voice-only applications. Customers like telecommunications companies can order custom cabling products for particular projects, and basic twisted pair wiring is available through hardware and electronics stores for hobbyists, contractors, and people performing home improvement projects.