Twisted pair cable classify in two types as:
- Unshielded Twisted Pair (UTP) Cable: UTP cable is the most general type of telecommunication medium which is mostly used. Although most familiar from its use in telephone system, its frequency range is suitable for transmitting both data and voice
A twisted pair consists or two conductors, generally copper, each with its own coloured plastic insulation. The plastic insulation is colour-banded for identifications shown in fig 1. colors are used both to identify the specific conductors in a cable end to indicate which wires belong in pairs and how they relate to other pairs in a large bundle.
A twisted pair consist of two conductors each surrounded by an insulating material.
Advantage of unshielded twisted pair cable:
1 its cost and ease of use
2 UTP is cheap
3 flexible and easy to install
4 Higher grades of UTP are used in many LAN technologies including Ethernet and Token Ring Fig 2. Shows a cable containing five unshielded twisted pairs
- Shielded Twisted –Pair (STP) Cable: Shielded Twisted –Pair (STP) Cable has a metal foil or braided-mesh covering that encases each pair of insulated conductors as shown in fig 3.
Fig 3 Shielded Twisted Pair (STP) Cable The metal casing prevents the penetration of electromagnetic noise. It also can eliminate the phenomenon called crosstalk. Which is the undesired effect of one circuit (or channel) on another circuit (or channel)? It occurs when one line pickup some of signals travelling down another line. This effect can be experienced during telephone conversations when one can hear other conversations in the background. To eliminate this effect shielding is used for each twisted pair cable.
Shielded twisted-pair cable has the same quality consideration and uses the same connectors as unshielded twisted-pair cable, but the shield must be connected to a ground. Materials and manufacturing requirements make STP more expensive than UTP but less Susceptible to noise.
