neon glow lamps (was TTL homebrew CPUs)

Jim Beacon jim at
Thu Jul 12 17:25:44 CDT 2007

From: "Tony Duell" <ard at>

> > You can also look out for tetrode thyratrons - these have an extra
> > that can be used to control the trigger point to some extent. The are
> > available as heated and cold cathode versions.
> IIRC, the very common 2D21 (EN91 in Europe) is a hot cathode tetrode
> xenon thyratron.
Yes, I've used these for a few experiments with oscillators and frequency
dividers - never seem to get much effect from the second grid though - I
suspect I need better regulated supplies, but it may come into its own in
ring counter circuits.


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