Telephony is the electronic point-to-point communication of audio signals. At the new millennium, the world has 750 million telephone lines, half of which are in the United States. Half the people in the world have never talked on a telephone! Every telephone "homes on" a switching office, either by copper wire or wireless link. Transmission lines, typically fiber or microwave links carrying thousands of simultaneous conversations, connect these switching offices to each other. Starting with Alexander Graham Bell's invention of the telephone in 1876, telephony has become a trillion-dollar-a-year worldwide industry. This industry consists of: (1) the carriers (in some countries, a government branch) that own the networks and provide telephone service and (2) the manufacturers of the switching and transmission equipment that the carriers use. Telephony and computing have had a synergistic relationship for about forty years as of 2002.

A telephone technician (c. 1991) adjusts a switching system...