Though it may seem strange to cover this elementary electrical topic at such a late stage
in this book series, I do so because the chapters that follow explore an older realm of digital
technology based on mechanical switch contacts rather than solid-state gate circuits, and a
thorough understanding of switch types is necessary for the undertaking. Learning the function
of switch-based circuits at the same time that you learn about solid-state logic gates makes
both topics easier to grasp, and sets the stage for an enhanced learning experience in Boolean
algebra, the mathematics behind digital logic circuits.