Screening is used to reduce the effects of electromagnetic interference (EMI) or electrical noise which can disrupt the transmission performance in some environments. This noise may be as a result of external interference from other electrical equipment or as a result of interference generated within the cable from adjacent pairs (cross talk).
Metal foil or braid may be used as a screen material, each with different properties and the screen may apply to the overall cable and/or to individual pairs in the cable.
The choice of screening is dependent on the environment where the cables are used and the applications they are required to run. For example, unscreened cables may be perfectly suitable for standard office applications, whereas screened cables may be preferred in industrial application or where higher performance transmission is required, or where data reliability and maximum throughput is paramount.
In all cases cables should be installed and terminated in accordance with internationally recognised standards.