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Chapter 2. Twisted Pair

Chapter 2. Twisted Pair

In this chapter, we will study and construct transmission channel models for twisted pair cables. The first type of twisted cable is the one used in existing in-house telephone wiring. This in-house twisted pair wiring usually extends from the entrance point of a telephone loop to telephone jacks distributed at many different rooms within a residence. For a multiple-pair twisted pair cable, the twist is usually applied to each individual pair with a particular twisting angle. For in-house telephone-wiring twisted pair cable, the twist is normally applied to all wires. Sometimes, flat cable with no twist is also used for in-house telephone wiring. The conventional wiring procedure of this in-house telephone loop extension is called star daisy-chain. At the center of the star is the telephone loop entrance point. From this center, a few branches of twisted pair cables are extended throughout the residence reaching all telephone jacks. Each branch usually connects a few phone jacks along one floor or within a particular region of residence involving multiple floors. Each star daisy-chain branch contains a few cascade twisted pair cable sections sequentially connected at phone jacks along the way. Sometimes, a branch can become multiple branches along the way. For this type of in-house telephone wiring, we will examine commonly used types of twisted pair cables, their transmission and crosstalk characteristics, networking topology, and impedances of telephony devices connected to this star daisy-chain network through telephone jacks. Based on this information, we will calculate transfer function, crosstalk loss, and channel capacity for a broadband communication link established between two phone jacks of the in-house telephone-wiring network.

The second type is the data-grade twisted pair cable. They are typically called Category 3 or Category 5 twisted pair cables. Category 3 and Category 5 twisted pair cables are used as transmission media for 10BaseT and 100BaseT Ethernet. Both require an active hub to connect all Ethernet transceivers together. The wiring topology of a 10BaseT or a 100BaseT Ethernet is a star. A hub with multiple transceivers is at the center of this wiring star. The star topology telephone wiring can often be found at recently completed homes. Data-grade twisted pair cables are often used in conjunction with the star topology telephone wiring. For data-grade twisted pair cables, we will examine their transmission and crosstalk characteristics and calculate the corresponding transfer function, crosstalk loss, and channel capacity for a point-to-point connection of a household dimension.


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