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.

Now, if you are system integrator, and you are setting up classic PBX network with

Traditional PBX and Centrex     Traditional Centrex and PBX are systems developed and installed before

Telephone networks are traditionally described as consisting of three parts: access, switching and transmission, also known as the access network, switching netwo

Despite of the fact that there are several thousands (if not millions) of conventional CO circuit switches and Private Branch Exchanges (PBXs) active, emerging programs are operating under VoIP protoc