Telephony

While the term telephony usually conjures images of point-to-point communication by voice, telephony actually describes a related set of technologies: telephones, switchboards, and telecommunication networks. Widely taken for granted in modern society, telephony is actually the backbone of modern telecommunications.

A telephone has a small microphone in the mouthpiece that converts the user's voice into electricity, which is then passed through the telephone network and converted back into sound for the person at the other end. As the number of users of a telephone system increases, it becomes more complex. Switchboards, first used in the 1880s, allowed all telephone users to be connected up to a central station. There, operators would connect one phone line with another, enabling users to talk. This process was automated in the early twentieth century, first through dial telephones and later through touch-tone phones. Today, phone companies use digital switching to route calls.

For promotional and practical purposes, it made sense that any point on the telephone system ought to be able to reach any other point in the system. On this basis, American Telephone and Telegraph (AT&T) appealed for and received monopoly status from the U.S. government for the better part of the twentieth century. In exchange, it had to follow the postal system model of “universal service,” where anyone who wanted to be hooked into the phone system could be. In practice, the expense of telephony prevented most Americans from having a phone in their own home until after World War II. Today, about 97 percent of American homes have active telephone service.

Some key twentieth-century ideas about communication were originally developed from the phone system. In 1909, the N.W. Ayer advertising agency ran a series of ads for long-distance telephony (then a new technology), calling telephone networks “highways of information.” The “information superhighway” moniker for the Internet is clearly a play on that phrase. More abstractly, mathematical studies of telephone-system circuits eventually grew into cybernetic communication theory. AT&T was mainly interested in getting its phone system to work better. How much noise could be present on a line before people could no longer understand one another? What was the best way of routing and managing the huge volume of calls passing through the telephone network? From these basic questions, mathematicians like Claude Shannon and Norbert Wiener developed cybernetics as a “science” of information and control. Although cybernetics is no longer in wide use as an omnibus theory of communication, descriptions of communication as following a path from sender to receiver still bear the mark of the telephone system.

“Wireless telephony” was first used as a term to describe the broadcasting of voice by radio in the first decade of the twentieth century. Today, it encompasses the use of cellular telephony and other technologies that allow people to take phones with them wherever they go. Although we think of it as telephony, wireless telephony is actually more like a form of radio. Wireless companies purchase a group of frequencies in the radio spectrum; rather than assigning a phone a permanent frequency, wireless companies make use of electronic and digital routing technologies to automatically and temporarily assign frequencies when a user wishes to make a call. As users move through a wireless service area (for instance, driving across town in a car), the frequencies to which their phones are assigned may change. This happens quickly and quietly enough to escape user notice. Once a phone call is being picked up by a wireless company's radio towers, it can be routed into a regular telephone network.

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