Shielded twisted pair or STP cabling is constructed using multiple techniques to significantly reduce signal interference. Because of these multiple shielding methods, shielded twisted pair cable provides better noise protection than unshielded twisted pair cable. This improved performance makes up for the increased installation cost.
Shielded twisted pair cabling uses increased shielding to reduce electromagnetic and radio frequency interference. Inside each cable is a bundle of wires divided into four pairs. Each pair of wires in the bundle is twisted together, which reduces crosstalk interference from other wire pairs. There are two common shielding configurations for STP cable. The most common type of shielding involves wrapping the inner bundle in foil, simply called a shielded twisted pair. The other common type of shielding involves shielding the entire bundle of wires with additional shielding of each twisted pair. The second type of cabling is called a screened shielded twisted pair. The cables are then finished with STP connectors.
Shielded twisted pair cabling is useful in environments where there is a high chance of electronic interference, such as radio stations and airports. As well as being protected from external interference, the shielding also keeps noise from exiting the cable, minimizing the chance of causing interference in other devices.