Induced Noise
What else could go wrong? Well obviously our cables are often run in noisy environments. Induced noise may come from any electrical source. The effect is to interfere with the shape of the data which may lead to bad decisions. Noise may add to the problems of pulse dispersion as caused by high frequencies. How is most noise eliminated?

What happens to induced noise? UTP attacks noise two ways. When noise is induced the signal is induced into both wires, each current, noise current in both wires will have its own electromagnetic field. By physically twisting the pairs, when the currents pass through this physical twist the electromagnetic fields of the two noise currents tend to eliminate each other or cancel each other out. This is a localised phase cancellation effect. The twisting of the pairs does eliminate the majority of the noise, however some currents still exists which is noise.

The way we get rid of this noise is by having a balanced cable, in other words both ends of the cable are terminated, and for UTP this is 100 ohms ± 15 ohms. Any currents that manage to get through the cable to the other end are dissipated by these resistors and the electronics is looking for the voltage in a differential format across both wires.