Definition of shielded twisted-pair (STP) cabling in Network Encyclopedia.
What is shielded twisted-pair (STP) cabling?
STP Cabling is 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 |
