Shielded Twisted Pair

- May 15, 2018-

Shielded Twisted Pair (STP) is a copper twisted pair that is widely used for data transmission. Twisted pair can be divided into two types which are unshielded twisted pair (UTP: Unshielded Twisted Pair) and shielded twisted pair (STP: Shielded Twisted Pair). In the physical structure, the shielded twisted pair has more full and/or shielded shields than the unshielded twisted pair. By means of shielding, attenuation and noise are reduced, thus providing a cleaner electronic signal and longer cable lengths. But shielded twisted pairs are more expensive, heavier and it’s not easy to install.

Shielded Twisted Pair is classified into two types, namely STP (Shielded Twisted-Pair) and FTP (Foil Twisted-Pair).  STP refers to shielded twisted pairs where each line has its own shield, while FTP uses shielded twisted pairs that are shielded as a whole. It should be noted that the shield only works if the entire cable is equipped with a shield and the two ends are properly grounded. Therefore, the entire system is required to be shielded devices, including cables, sockets, jumpers and patch panels, etc. At the same time, the building needs to have a good grounding system. However, it is difficult to perfectly ground it all in actual construction. Under normal good grounding conditions, the shielding system's ability to resist external coupling noise is 100-1000 times that of unshielded systems. Even if the shielding layer is not grounded or has poor grounding, the shielded wiring system withstand capability can still be used for unshielded wiring systems more than 10 times.

The outer layer of the shielded twisted pair cable is wrapped in aluminium foil to reduce radiation, but it does not completely eliminate radiation. The price of shielded twisted pairs is relatively high, and it is more difficult to install than unshielded twisted pair cables. It must be equipped with special connections and construction techniques that support shielding. When the shielded twisted pair cable is installed, the shielding layer of the shielded twisted pair must be grounded, but shielding the twisted pair in a physical area with a large amount of electromagnetic interference provides a convenient, economic, and effective solution.