From the point of view of the average telephone engineer, the phone system is divided into two principal parts: outside plant (the local loops and trunks, since they are physically outside the switching offices) and inside plant (the switches), which are inside the switching offices. We have just looked at the outside plant. Now it [...]
In the aboriginal canicule of cilia optics, every blast aggregation had its own proprietary optical TDM system. After AT&T was burst up in 1984, bounded blast companies had to affix to assorted long-distance carriers, all with altered optical TDM systems, so the charge for acclimation became obvious. In 1985, Bellcore, the RBOCs analysis arm, began [...]
WDM technology is wonderful, but there is still a lot of copper wire in the telephone system, so let us turn back to it for a while. Although FDM is still used over copper wires or microwave channels, it requires analog circuitry and is not amenable to being done by a computer. In contrast, TDM [...]
Economies of scale play an important role in the telephone system. It costs essentially the same amount of money to install and maintain a high-bandwidth trunk as a low-bandwidth trunk between two switching offices (i.e., the costs come from having to dig the trench and not from the copper wire or optical fiber). Consequently, blast [...]
Since 1996 in the U.S. and a bit later in other countries, companies that wish to compete with the entrenched local telephone company (the former monopolist), called an ILEC (Incumbent LEC), are free to do so. The most likely candidates are long-distance telephone companies (IXCs). Any IXC wishing to get into the local phone business [...]
The alternative approach, called DMT (Discrete MultiTone), is illustrated in Fig. 2-28. In effect, what it does is divide the available 1.1 MHz spectrum on the local loop into 256 independent channels of 4312.5 Hz each. Channel 0 is used for POTS. Channels 1–5 are not used, to keep the voice signal and data signals [...]
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