There on the X-ray film, he could see that inside an unassuming metal bar that ran the length of the typewriter was the most sophisticated exploit he, hell, anyone at the agency, had ever seen. The bar contained a tiny magnetometer, a device that measures the slightest distortions in the earth’s magnetic field. The magnetometer was converting the mechanical energy from each typewritten keystroke into a magnetic disturbance. And next to it was a tiny electronic unit recording every disturbance, cataloging the underlying data, and transmitting the results in short bursts via radio to a nearby
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