What is Shielded Twisted Pair (STP)?
Shielded twisted pair (STP) is a special type of copper telephone and local area network (LAN) cabling used in some commercial installations. It adds an outer jacket or shield to the ordinary twisted pair cable, which acts as a ground.
Twisted pair is the common copper wire that connects many computer networks and telephone companies. To reduce crosstalk, or electromagnetic induction, between the paired wires, two insulated copper wires are twisted around each other. Each signal on a twisted pair requires two wires.
Unlike unshielded twisted pair (UTP), shielded twisted pair also wraps the wires in a shield and grounds them to further reduce electromagnetic and radio frequency interference. STP cable is more expensive and more difficult to install than UTP cabling.
Unshielded twisted pair
Shielded twisted pair cable has an additional outer shield added to the standard twisted pair cable.
How to install shielded twisted pair cabling?
Because some telephone sets or desk locations require multiple connections, twisted pair cabling is sometimes installed as two or more pairs – all within a single cable. Businesses often use shielded twisted pair when installing their cabling systems, while homes more commonly use UTP cable.
Today, twisted-pair cabling is often installed in homes as two pairs of cables. The extra pair allows another line to be added if needed – perhaps for a modem.
Twisted pair cable, whether UTP or STP, when it is packaged into multiple pairs, each pair has a unique color coding. Different uses, such as analog, digital, and Ethernet, require different multiples of wire pairs. Therefore, color coding makes it easier to distinguish wire pairs.
Although twisted pair is usually associated with home use, businesses often use higher-grade twisted pair for horizontal cabling in LAN installations because it is less expensive than coaxial (coax) cable. Coaxial and fiber optic cabling are the main alternatives to twisted pair.
In electrically noisy commercial environments, shielded twisted pair cabling is used with RS-449, RJ-45, RS-232, and RJ-11 connectors to minimize interference.
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