1.1 A BRIEF HISTORY OF COMMUNICATIONS

Although communication can be defined in many ways, here we define it simply as the exchange of information. Information may take many forms, including spoken words, written text, images, sound, video, or digital data. Regardless of its form, the purpose of communication is to allow one person, device, or organization to share information with another.

Communication has been fundamental to the development of civilization. Every society has depended upon the ability to exchange information—for trade, government, education, science, defense, and social interaction. Throughout history, improvements in communication have often transformed the way people live and work. Faster communication has enabled larger communities to cooperate, businesses to expand beyond local markets, governments to administer larger territories, and scientific knowledge to be shared more rapidly. In many respects, the history of civilization is closely linked to the history of communication.

In everyday life, communication over short distances is usually straightforward. People can speak directly to one another, exchange written documents, or use visual signals such as gestures and signs. As distance increases, however, these simple methods become impractical. A person cannot normally speak across a city, see across a mountain range, or carry on a conversation with someone on another continent. Overcoming the limitations imposed by distance has therefore been one of humanity's oldest engineering challenges.

The solution has been the development of communications systems—systems that carry information from one location to another using an appropriate transmission medium. These systems may employ electrical conductors, optical fibers, radio waves, satellites, or computer networks, but they all perform the same fundamental task: transferring information accurately, reliably, and efficiently between separated locations.

Historically, such systems were known as telecommunications systems, using the Greek prefix tele- meaning far. The term reflected the original objective of extending communication over distances much greater than those possible by direct human interaction. Today, however, the distinction is less obvious. Many modern communications technologies, such as Bluetooth and Near Field Communication (NFC), operate over only a few meters or even a few centimeters, while others, including satellite systems and undersea fiber-optic cables, routinely span thousands of kilometers. As a result, the shorter term, communications, has become more common.

Although modern communications systems differ enormously in their implementation, they all address the same fundamental problem: how to represent information, transport it through a communication channel, and reconstruct it accurately at its destination. Understanding how engineers have solved this problem over time provides valuable insight into the operation of today’s communications systems. The sections that follow trace the major stages in this remarkable technological evolution, from human messengers and optical signaling to global digital networks connecting billions of people and devices.