shielded twisted-pair (STP) cabling

Definition of shielded twisted-pair (STP) cabling in The Network Encyclopedia.

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What is shielded twisted-pair (STP) cabling?

Twisted-pair cabling with additional shielding to reduce crosstalk and other forms of electromagnetic interference (EMI). The outer insulating jacket contains an inner braided copper mesh to shield the pairs of twisted cables, which themselves are wrapped in foil.

Shielded twisted-pair (STP) cabling is more expensive than unshielded twisted-pair (UTP) cabling. It has an impedance of 150 ohms, has a maximum length of 90 meters, and is used primarily in networking environments with a high amount of EMI due to motors, air conditioners, power lines, or other noisy electrical components. STP cabling is the default type of cabling for IBM Token Ring networks.

STP cabling comes in various grades or categories defined by the EIA/TIA wiring standards, as shown in the following table.

STP Cabling Categories

Category Description
IBM Type 1
Token Ring transmissions on AWG #22 wire up to 20 Mbps
IBM Type 1A
Fiber Distributed Data Interface (FDDI), Copper Distributed Data Interface (CDDI), and Asynchronous Transfer Mode (ATM) transmission up to 300 Mbps
IBM Type 2A
Hybrid combination of STP data cable and CAT3 voice cable in one jacket
IBM Type 6A
AWG #26 patch cables

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