Those would most likely be inductors or transformers. It is mentioned in the article how the simplistic Figures 2 & 3 magnetic amps would act as a transformer.

Those would most likely be inductors or transformers. It is mentioned in the article how the simplistic Figures 2 & 3 magnetic amps would act as a transformer. https://en.wikipedia.org/wiki/Toroidal_inductors_and_transformers https://en.wikipedia.org/wiki/Toroidal_inductors_and_transfo...