POTS and loops have already been discussed in great detail, and it’s time to look at PSTN’s trunk side. The Figure shown below illustrates Bell System switching centers’ five-level hierarchy.

In our article few days ago where we talked about Loops and Trunks & Circuit switching,  we finished our article on discussing concepts for CO, and how it were made since the most humble beginnin

We’ll start this series of articles with a basic model of PSTN - PSTN stands for (Public Switched Telephone Network) and build on it in subsequent posts. In figure below, a