17.1. Introduction to Voice Networks
I know some of you do not use voice often or at all. For that reason, I want to talk about a few basic voice functions before I dig too far into the chapter topics. Historically, enterprise phone systems all ran off of a private branch exchange (PBX). The PBX provided switching between the company's analog telephones. The switching connects the company's internal phones to each other when someone makes a call or sends the call out to the phone company if the call is not destined for a private number. Once a phone call is transmitted out of the company's system onto the phone company's network, usually called the public switched telephone network (PSTN), time-division multiplexing (TDM) is used to connect ...
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