How Howard Armstrong Invented Positive Feedback

Positive feedback in electronics, or when a small change is feed into a loop to magnify itself is a vital part of electrical engineering.  But where did it come from and how does it work?  I actually know the answer to that: it was created by a 20-year-old college student named Howard Armstrong in his parent’s attic on a summer night in 1912! This is a story of a childhood book, a rule-breaking neighbor, an inspiring immigrant, and a very, very, very important coil of wire. 

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