Logic Switching Circuits

Today's digital circuitry is built with electronic technology that the telephone engineers of the 1930s and the pioneer computer designers of the 1940s would have thought to be magic. The first real digital technology took the form of electromagnetic relays in telephone switching exchanges. Then came vacuum tube digital circuitry, discrete transistors, integrated transistor circuits, and so on.

But the one thing that remains the same is the math, the Boolean algebra that is the central star of this book. This chapter describes the technology that Shannon himself used in his switching analyses. It covers Switches and the logical connectives, a classic switching design problem, electromagnetic relay, the ideal diode and the relay logical AND and OR, and the bi-stable relay latch.