Electronic circuits are dynamical systems. There is a long tradition to investigate electronic circuits using the emerging dynamical system theory since the 1930s with the contributions by Balthazar van der Pol  and Aleksandr Andronov’s school  to only quote the most well known. Henri Poincaré, who may be considered as one of the fathers of the dynamical system theory, investigated himself the equation governing a singing arc . Later, books by Nicholai Minorsky  and Chihiro Hayashi,  were important in popularizing the dynamical systems approach in electronic circuits.
Early contributions to chaos by people investigating electronic circuits were reviewed in Ref. .