d between two remotely located parties. To converse with others, even if they are not physically nearby, is a basic human need. The invention of telephony clearly had the potential to become a great business success [1]. This chapter is an introduction to telephony, a complete telecommunications system with its specific technologies, business dynamics and policy issues. Moreover, most present telecom- munications operators and manufacturers trace their roots to telephony services and equip- ment, and many of the technologies and processes developed for telephony systems are still in use. Therefore an examination of the telephony system can greatly inform our study of present day broadband telecommunications. Many technologies have been developed to enable and enhance telephony systems. Initially technologies were focused on sound-to-electricity-to-sound conversion. Research and develop- ment into call initiation, called party information, switching, and call termination were also important. Later on signal modulation, multiplexing, network dimensioning as well as automatic switching improved telephony operations. Most of these technologies are important to provision of wireless and fixed broadband telecommunications services. An introduction to these early telephony technologies will be given in this chapter and will be further expanded in later chapters. Sound and Electrical Signals A telephone comprises a microphone which converts sound(human voice) into an electrical signal, and a speaker which converts the electrical signal back to sound, as shown in an early illustration of Bell's telephone in Figure 3.1. As noted above, Bell improved on technologies that made these two conversions possible and facilitated higher quality voice communications compared with earlier devices. The generated electrical signal is transported to a receiver using a physical medium - commonly a twisted pair of copper wires, a medium used since the days of Bell. Copper wires have good electrical conductivity, and are robust, flexible a