Activities on circuit theory in Japan

In Japan, systematic study on circuit theory started in the early Twenties and many pioneer research works have been made up to now. This paper reviews the historical aspect of the circuit theory developed in Japan during the past half centuries. The research activities in Japan have covered the wide range of circuits and systems, such as filter theory, network theory, graph theory or combinatorial mathematics, and computer aided design for electrical circuits. It is rather surprising that a number of excellent pioneer contributions on circuit theory has been done by Japanese researchers and has been applied to practice widely.