Noise
Noise is unwanted electrical signals that alter the shape of the transmitted signals on the network.
Noise on the cable can be produced by many different sources, such as other wire pairs, fluorescent lights, radios, electronic devices, heaters, and air conditioning units.
Cable testers can listen for noise on the wire. To perform a test for cable noise, the cable should be unplugged from the network jacks and punch panel. The cable tester then listens for noise on the cable.
If noise is found on the cable, the path of the wire should be traced to determine if there is any possible noise source in the area. Unplug devices where possible to see if the noise disappears.