Another technological triumph is the cell phone, a radio-linked device that is taking the world by storm. Old-style mobile telephones received their signals from a single powerful transmitter that covered an area about 50 miles in diameter, an interference-prone method that provided enough channels to connect only a couple of dozen customers at a time. Cellular technology, by contrast, uses low-powered base stations that serve "cells" just a few square miles in area. As a customer moves from one cell to another, the phone switches from a weakening signal to a stronger one on a different frequency, thus maintaining a clear connection. Because transmissions are low powered, frequencies can be reused in nonadjacent cells, accommodating thousands of callers in the same general area.
Although the principles of cellular telephony were worked out at Bell Labs in the 1940s, building such systems had to await the arrival of integrated circuits and other microelectronic components in the 1970s. In the United States, hundreds of companies saw the promise of the business, but government regulators were very slow in making a sufficiently broad band of frequencies available, delaying deployment considerably. As a result, Japan and the Scandinavian countries created the first cellular systems and have remained leaders in the technology. At the start there was plenty of room for improvement. Early cell phones were mainly installed in cars; handheld versions were as big as a brick, cost over a thousand dollars, and had a battery life measured in minutes. But in the 1990s the magic of the microchip drove prices down, shrank the phones to pocket size, reduced their energy needs, and packed them with computational powers.
By the year 2000, 100 million people in the United States and a billion worldwide were using cell phones—not just talking on them but also playing games, getting information off the Internet, and using the keyboard to send short text messages, a favorite pastime of Japanese teenagers in particular. In countries where most households still lack a telephone— China and India, for example—the first and only phone for many people is likely to be wireless. Ultimately, Alexander Graham Bell's vision of a wired world may yield to a future in which, for everyone, personal communication is totally portable.