basic about twisted pair cables

Twisted pair cable is a type of cable in which two conductor’s of a single circuit are twisted together for the purpose of canceling out electromagnetic interference from external sources.

For example, electromagnetic radiation from un shielded twisted pair cables, and cross-talk between neighboring pairs.

In pair operation for balancing, the two wires carry equal and opposite signals and the destination detects the difference between the two. This is known as differential mode transmission. Noise sources introduce signals into the wires by coupling of electric or magnetic fields and tend to couple to both wires equally.

This method starts to fail when the noise source is close to the signal wires.The closer wire will couple with the noise more strongly and the common-mode rejection of the receiver will fail to eliminate it. This problem is especially apparent in telecommunication cables where pairs in the same cable lie next to each other for many miles.

One pair can induce cross-talk in another.