Creating the Motorola car radio, Galvin emerged as the premier producer of car radios in the 1930s. Galvin also invented the walkie-talkie, producing some 40,000 during World War II. In 1947, Galvin introduced the first practical television set under $200, helping increase the companyís sales to $47 million. Wishing to overcome his firmís dependence on vacuum tubes, Galvin developed transistors to be used in car stereos. Building on this new technological advancement, Motorola entered the semiconductor field.