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 Beginning in the 1980s, however, cheap AM transistor radios were superseded by devices with higher audio quality such as portable CD players, personal audio players, boomboxes, and (eventually) smartphones, some of which contain radios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 heyday of the big alternator radio transmitters was around 1918. World War I had brought home to nations the strategic importance of radio communication, as without it they could easily be isolated by enemies cutting their submarine telegraph cables. This precipitated a postwar building boom of large transcontinental alternater radio stations. However these expensive behemoths were obsolete even as they were installed. The invention of the triode vacuum tube in 1906 by Lee De Forest, and the feedback oscillator circuit in 1912 by Edwin Armstrong and Alexander Meissner, made possible smaller and cheaper vacuum tube transmitters which by the end of World War 1 could produce as much radio power as the alternators. By 1921 the Marconi Co. had installed 100 kW vacuum tube transmitters for transatlantic message traffic at its stations at Carnarvon, Wales and Glace Bay, Newfoundland. Due to their huge capitol costs, legacy alternator transmitters remained in use through about 1930. It is not known when the last Goldschmidt machine was retired.