Word: radar
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...Radar, one of the most heavily curtained of war secrets, was bared for a quick peek by the Army and Navy. The word stands for "radio detecting and ranging." Basis of operation, a high-frequency radio ray, scanning air or sea, bounces back from objects it strikes: e.g., ships or planes. Radar measures the infinitesimal fraction of a second this takes (at 186,000 miles an hour), thus calculates distance as well as direction. Both Britain and Germany have similar devices...
Promika has not yet successfully supplanted mica except for most types of radio condensers. But with literally billions of those needed for radar, walkie-talkies, inter-communicators, etc., this is a huge step forward. Natural mica "fails" at lower temperatures than Promika. Moreover, 1 lb. of Polectron replaces 10-15 lb. of natural block mica (on which rejects and wastage are very high), thus costs less than Indian mica...