PSTN and VoIP

In the 1940s, a consortium of leaders in the telecommunications industry and in government standardized how customers would be assigned telephone numbers. The telephone number identified a specific pair of wires out of millions of pairs of wires, and a specific phone company switch out of thousands of such devices.

The term circuit-switched describes this setup of circuit wiring, switching devices, and telephone number assignment. The PSTN is sometimes referred to as the circuit-switched or switched network. Because today’s public phone system is still circuit switched, it still relies on the same basic system for telephone number assignment.

VoIP introduced dramatic changes in how the network is used and, over time, VoIP could force changes in how numbers are assigned. With VoIP, phone numbers are no longer tied to specific wires and switches. VoIP routes calls based on network addresses, and phone numbers are simply used because that is what people are familiar with. (VoIP takes care of translating a phone number into a network address.) In the future, as more and more people adopt VoIP-based systems, we may see dramatic changes in phone numbering.