The TR-55, released in 1955, was Sony's first transistor radio, and the first to be made in Japan. The use of transistors rather than vacuum tubes allowed the device to be much smaller than earlier radios, and allowed them to be the first truly portable radio from Japan.
The TR-55 used 5 transistors designed in house by Sony, the technology having been licensed from Bell Labs. This made Sony the first company to produce commercial transistor radios from the ground up: Regency had an earlier transistor radio but bought the transistors from Texas Instruments. Printed circuit boards were used, which was unusual for the time.