Figure 8.1Pentagon of Power
First, a little history. The electromechanical relay, discussed in the previous chapter, was originally invented to extend telegraph signals. The weakening DC signal from the previous station was applied to the coil of a relay in the receiving station, which would clatter its contacts with dots and dashes, sending the signal down line with new energy. A relay is called a relay because it “relayed” telegraph signals in this manner. About the same time use of the telegraph was becoming widespread, George Boole developed a mathematical system of logic based ...
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