permitted height 中文意思是什麼
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The cathode ray tube had just been fitted with a hot cathode, which permitted operation at 300 volts instead of the previously required 10, 000, the lower voltage obtainable from a stack of dry cells of less than ceiling height
（那時）剛剛有用一種熱陰極作成的陰極射線管，這種熱陰極不需要以前要求的10 ， 000伏，可以在300伏電源下工作，這種低電壓可以由不再堆得天棚高那末多的干電池來獲得。
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