ABSTRACT
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5.1 Vacuum Fluorescent Displays The vacuum fluorescent display (VFD) was invented in Japan in 1965, and is now a practical display device.1 In the beginning, there was the single-digit round tube, which was later developed into the multi-digit round tube and then into the flat multi-digit panel.2 At first, these devices were used almost entirely in calculators, but now they have a wide range of applications, including audio and video equipment, household electronics, automobiles, office equipment, and instrumentation.3
