h often requires a suitable economic and regulatory environment (Geeslin, The telecommunications network must be designed to evolve 1989). with its technological base, leading to the concept of open network architecture. The network should be able to provide new services and respond in real time to changes in traffic flow, This chapter provides an overview of the telecommunications and to changes from switched to permanent or semi-permanent field, some of the topics then being developed in greater detail in connections, and all this must be achieved under control of the subsequent chapters in this book. service provider or the customer. Investment decisions are based on short payback periods. There must be rapid growth in the revenues resulting from introduc- 11.2 The telecommunications model tion of a service based on a new technology. Telecommunications is a complex entity containing many inter- Many telecommunication technologies are being developed woven factors. Figure 11.1 shows a simplified representation of a which will form the network of the future, such as SDH, broadband telecommunications model, which illustrates the 'chicken and egg' ISDN using ATM, and universal mobile communications. These syndrome occurring in any high tech industry. developments in their turn are dependent on enabling component Services or customer demand is at one end of the model and technologies such as in photonics (optical components and optical enabling technology at the other. Which comes first? Which is the fibre), integrated circuits, software structures and languages and chicken and which is the egg? Do the services pull through the software development processes. technology or is it that, once a technology is discovered, the corre- Telecommunications is creating an information oriented society, sponding services follow automatically? As in all such consider- resulting in a change in business practices and in individual life ations there is no single answer which fits every occasion. styles. The customer is becoming inc