|ignitron (ɪɡˈnaɪtrɒn, ˈɪɡnɪˌtrɒn)|
|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|
|[C20: from |
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
|a printed punctuation mark (‽), available only in some typefaces, designed to combine the question mark (?) and the exclamation point (!), indicating a mixture of query and interjection, as after a rhetorical question.|
electronelectron tube functioning as a rectifier to convert alternating current (AC) to direct current (DC). Each conduction cycle is started by an external voltage applied to the igniter, a small electrode touching the tube's cathode, which is a pool of mercury. Electrons released by the igniter from the surface of the mercury initiate a conducting arc through the tube. The arc lasts until voltage on the ignitron's plate has been reduced to the point that the arc can no longer be sustained
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