From POTS to PANS: A commentary on the evolution to Internet telephony

A PSTN phone can generate only a small set of signaling events and tones, and cannot receive or process signaling Of;of any sophistication. Packet phones, on the other hand, can receive and process signaling automatically and also send signaling out of band as a separate set of If packets. Evolution from plain old telephony services (POTS) to IP telephony therefore promises some pretty amazing new services (PANS). It will nevertheless take many years to transition to a purely packer-based environment. The authors describe aspects of the evolution of telephony networks and services as they relate to the underlying technology.