The portability of cellular telephones provides users with the ability to make calls from almost anywhere and Motorola was built on portability. The company made car radios in the 1930s and portable radios called walkie-talkies for the U.S. military during World War Two, and played a major role i

Before 1954, so-called portable radio receivers used vacuum tubes to receive and amplify signals. The large batteries needed to power most tubes made radios large and heavy. Receivers built with subminiature tubes existed but were expensive. The invention of transistors in 1947 allowed engineers