Diagram showing how the mixed-mode operating system works in different seasons at the West Berkeley Public Library. (Image courtesy Harley Ellis Devereaux)

Diagram showing how the mixed-mode operating system works in different seasons at the West Berkeley Public Library. (Image courtesy Harley Ellis Devereaux)

Diagram showing how the mixed-mode operating system works in different seasons at the West Berkeley Public Library. (Image courtesy Harley Ellis Devereaux)