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A single-anode, mercury-vapor rectifier in which current passes as an arc between the anode and a mercury-pool cathode, used in power rectification.
(Electronics) 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 igniter + electron]
ig•ni•tron(ɪgˈnaɪ trɒn, ˈɪg nɪ trɒn)
a rectifying vacuum tube with an auxiliary electrode projecting into a pool of mercury that conducts current when the anode is positive.