The Sony Corporation was founded by engineers Masru Ibuka and Morita Akio in 1946 as the ‘Tokyo Telecommunications Engineering Corporation’ and initially operated as small repair centre for war-damaged radios and sets. With a mission to ‘do what has never been done before,’ Sony were responsible for launching the consumer micro-electronics industry and in 1957 produced the world’s smallest transistor radio, the TR-63 pocket-sized radio. In 1952, Sony’s founders made the decision to licence the transistor, an exciting new semi-conductor device owned by the American company, Western Electric. This led to the development of Sony’s first hugely successful product line of portable transistor radios. Although the portable radio had already been realised by the American manufacturers Idea Inc. and Texas Instruments in 1954, Sony’s version, the TR-55, launched in 1955 was more commercially successful due to its inexpensive, compact design. Where once the radio was a centrepiece around which people would congregate and socialise, the transistor radio provided a new sense of freedom for listeners, offering both privacy and portability to its users.

Superheterodyne circuits were invented by Edwin Armstrong when he was serving with the U.S. Army Signal Corps in France during WWI. In a superheterodyne circuit, the incoming high frequency radio signal is mixed with a lower frequency signal generated by the radio itself. The ‘Superhet’ became one of the most common forms of radio receiver and virtually all broadcast radio receivers, as well as televisions have used the superheterodyne principle as the basis of their operation. Minimalist and distinctive in design, the 2R-21 is also significant for its inclusion of a micro transistor.