l be used for telephone calls in addition to Internet surfing. This requires telecommunications network operators, including cellular net- work operators, to change their strategies from telephone and data transmis- sion to complete service and information content provision. These services will contain Internet portals and location-based services, such as information on the nearest fast-food restaurant, in cellular networks. For the future development of the telecommunications business, we must pay attention to customer services that technology can provide, not technology itself. Many good technologies, which we explain in later chap- ters, have not been successful because ordinary subscribers have not viewed them as attractive. Examples of these technologies are ISDN and wireless application protocol (WAP) services. On the other hand, some services, such as the WWW, have grown very rapidly. We have to keep in mind that only attractive services make new technologies successful. 1.7 Problems and Review Questions Problem 1.1 List two or more electrical telecommunications systems that provide (a) bidi- rectional and (b) unidirectional service. Problem 1.2 What were the three main developments in communications technologies during the last 20 years? Explain why you think SO because this is a matter of opinion. Problem 1.3 What are the most important advantages of global telecommunications standards? Problem 1.4 Why is it often difficult to achieve a common understanding of and approve global standards? Explain both political and business interests. References Carlson, A. B., Communication Systems: An Introduction to Signals and Noise in Electrical Communication, New York: McGraw-Hill, 1986. Introduction to Telecommunications Network Engineering [2] Tanenbaum, A. S., Computer Networks, 3rd ed., Upper Saddle River, NJ: Prentice Hall, 1996. Comer, D. E., Internetworking with TCP/IP: Principles, Protocols, and Architecture, 4th ed., Upper Saddle River, NJ: Prentice Hall, 2000. Steele, R., and L. Hanzo, Mobile Radio Commu