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Computer Network 2021
3.2.1.1 Shielded Twisted-Pair Cable
Shielded twisted-pair (STP) cable contains four pairs of thin, copper wires covered in
color-coded plastic insulation that are twisted together. Each pair is wrapped in metallic foil,
and then the four pairs are collectively wrapped in another layer of metallic braid or foil. This
layer is wrapped with a plastic outer jacket. Figure 3-1 illustrates an example of STP.
Figure 3-1 shown a Shielded Twisted-Pair Cable Structure
Screened twisted-pair (ScTP), also known as foil twisted-pair (FTP), is a variation of STP.
ScTP is essentially STP with just one layer of foil shielding around the set of all four-wire pairs, as
shown in Figure 3-2. The shielding in both STP and ScTP reduces unwanted electrical noise. This
noise reduction provides a major advantage of STP over unshielded cable.
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