Regarding the transmission distance of twisted-pair cables:
A twisted-pair cable consists of a pair of mutually insulated metal wires twisted together. This approach not only resists some electromagnetic interference from the outside world but also reduces mutual interference between multiple pairs of twisted wires. When two insulated wires are twisted together, the interference signal acting on these two intertwined wires is consistent (the interference signal mentioned here is called common-mode signal). In the differential circuit receiving the signal, the common-mode signal can be eliminated, thereby extracting the useful signal (differential-mode signal).
The function of twisted-pair cables is to make the noise generated by external interference on the two wires identical, so that the subsequent differential circuit can extract the useful signal. The differential circuit is a subtraction circuit where signals in the same direction (common-mode signals) at the two input terminals cancel each other out (m-n), and signals in opposite directions are equivalent to x-(-y), resulting in enhancement. Theoretically, in twisted-pair cables and differential circuits, m=n and x=y, which is equivalent to the complete elimination of interference signals and the doubling of useful signals. However, there are certain differences in actual operation.
In a cable sheath, different pairs of wires have varying twist lengths. Generally, the twist length ranges from 38.1mm to 140mm, twisted in a counterclockwise direction, with the twist length of adjacent pairs being within 12.7mm. The length of one twist cycle in twisted-pair cables is called the pitch. The smaller the pitch (the denser the twist), the stronger the anti-interference capability.