Local telephone companies use legacy local Class 5 switches to provide service to customers who are still using analog telephones on copper cabling. Providers initially replaced core toll switches (also called tandem switches in North America and transit
switches in Europe) with Voice over Internet Protocol (VoIP) technology. One reason they replaced toll switches first, rather than Class 5 switches, is that there are far fewer voice switches in the core than in last-mile networks. Thus, costs are lower because
there are fewer switches to replace and maintain.
Many Class 5 switches connect to a single, centralized switch in the core. In addition, VoIP switches did not have the large number of features that telephone companies desired at that time. This is not an issue for toll switches, which primarily set up and tear down large numbers of calls between central offices.
