Transistor radio
A transistor radio is a small portable radio receiver that uses transistor-based circuitry. Following their development in 1954, made possible by the invention of the transistor in 1947, they became the most popular electronic communication device in history, with billions manufactured during the 1960s and 1970s. Their pocket size sparked a change in popular music listening habits, allowing people to listen to music anywhere they went. Beginning in the 1980s, however, cheap AM transistor radios were superseded by devices with higher audio quality such as portable CD players, personal audio players, boomboxes, and (eventually) smartphones, some of which contain radios themselves.
Goldschmidt alternator
The Goldschmidt alternator or reflector alternator, invented in 1908 by German engineer Rudolph Goldschmidt, was a rotating machine which generated radio frequency alternating current and was used as a radio transmitter. Radio alternators like the Goldschmidt were some of the first continuous wave radio transmitters. Like the similar Alexanderson alternator, it was used briefly around World War I in a few high power longwave radio stations to transmit transoceanic radiotelegraphy traffic, until the 1920s when it was made obsolete by vacuum tube transmitters.