An electrical switch is any device used to interrupt the
flow of electrons in a circuit. Switches are essentially binary devices:
they are either completely on ("closed") or completely off ("open"). There
are many different types of switches, and we will explore some of these
types in this chapter.
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.