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ignitron

American  
[ig-nahy-tron, ig-ni-tron] / ɪgˈnaɪ trɒn, ˈɪg nɪ trɒn /

noun

Electronics.
  1. a cathode-arc vacuum tube with an auxiliary electrode projecting into a pool of mercury: it conducts current when the anode is positive.


ignitron British  
/ ɪɡˈnaɪtrɒn, ˈɪɡnɪˌtrɒn /

noun

  1. a mercury-arc rectifier controlled by a subsidiary electrode, the igniter, partially immersed in a mercury cathode. A current passed between igniter and cathode forms a hot spot sufficient to strike an arc between cathode and anode

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of ignitron

First recorded in 1930–35; igni(ter) + -tron