Twisted-pair
The historical foundation of the public switched telephone network (PSTN) lies in the twisted-pair, and even today most people who have access to networks access those networks through a local loop built on twisted-pair. So, although twisted-pair has contributed a great deal to the evolution of communications, advanced applications on the horizon require larger amounts of bandwidth than twisted-pair can deliver, so the future of twisted-pair is diminishing. Figure 3.1 shows an example of four-pair UTP.
Figure 3.1. Twisted-pair
The total usable frequency spectrum of twisted-pair copper cable is about 1MHz (that is, one million cycles ...
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