Easily carried in purse or pocket, cellular telephones (see entry under 1900s—The Way We Lived in volume 1) are hand-held, wireless devices that became increasingly common throughout the world in the 1990s. Cellular phones permitted users to make and receive telephone calls from almost any location. Cellular phones are technically two-way radios (an evolution of the wrist radios worn by comic-strip detective Dick Tracy (see entry under 1930s—Print Culture in volume 2) because they rely on signals from antennas that have been installed across the landscape. Antennas are placed on buildings in cities and towns or on freestanding towers in rural areas. Each antenna emits a microwave signal that saturates the area, or cell, surrounding it. Signals are broadcast over a large number of channels, permitting many conversations to take place simultaneously, as with standard telephone service. As a caller travels across the service area, the...