Since World War II, no invention has made a larger impact on the communications field than the transistor, which replaced old-fashioned vacuum tubes in electronic equipment. The transistor revolutionized electronic technology and created a billion dollar industry that sells everything from popular consumer items--such as home computer games, pocket calculatos, and portable stereos--to the complex electronic systems used by business and industry.

In the 1930s researchers were aware of the limitations of vacuum tubes, which were used to increase electric current, a process called amplification, and to force it to flow in only one direction, which is known as rectification. Vacuum tubes were bulky and fragile, and they consumed a lot of power. The tubes also had a tendency to overheat, so they needed large, reliable cooling systems, and when radar was developed during World War II, vacuum tubes were unable to provide the range of frequencies, power...