Why are the wire pairs in a UTP cable twisted together?

The twisting of wire pairs in an unshielded twisted pair (UTP) cable is primarily designed to protect against electromagnetic interference (EMI). This twisting helps to reduce the impact of noise and crosstalk that may be induced by external sources or adjacent wire pairs within the cable. Each twist acts as a countermeasure to interference, as the electromagnetic fields generated by the currents in the wires cancel each other out, thereby enhancing the signal quality.

Furthermore, by following this twisted design, UTP cables can maintain a consistent characteristic impedance, which helps in preserving the integrity of the signal over longer distances. In practice, the twisting makes UTP cables effective for networking applications where long runs of wiring are needed, especially in environments where there may be other electromagnetic sources nearby.