The assembled TR-2K

Sony launched the first Japanese transistor radio, the TR-55, in September 1955. Less than a month later, Sony kicked off sales of the little-known TR-2K transistor radio kit as well. The TR-2K was Japan's first transistor radio kit and, when assembled, represented Japan's second pocketable ultra-compact transistor radio.

Transistor radios promised massive size reductions, and realizing units that would fit in the pocket was the dream of every technician involved in the commercialization process.
Initially, however, it proved impossible to make Japan's -- and Sony's -- first transistor radio, the TR-55, pocket-sized. To create smaller radios, it was not enough to make only the transistors smaller. The speaker, condensers, transducers and other parts also had to be reduced in size. Adopting what might in one sense be called an aggressive approach, Sony engineers achieved greater reductions in scale via a bold strategy that eliminated the speakers to create an earphone-only radio. At 5,700 yen, the TR-2K was cheaper than the 19,900 yen TR-55 because, in addition to enabling customers who bought the product to assemble it themselves using only an soldering iron, amplification for the speaker was unnecessary and it was possible to use cheaper transistors. However, it turned out that although the catalog said users could assemble the unit in four hours, customer service personnel were kept extremely busy with inquiries from customers who, at the time, were not used to electrical circuitry. These troubles passed quickly and two years later, Sony came up with the 13,800 yen "pocketable" TR-63 radio, which had a speaker and became a huge best-seller.