Neon logic

From: Rick Bensene <>
Date: Fri Feb 28 17:04:00 2003

There's no such thing as an Anita Mk IV(4). The first machine that was sold
was the
Anita Mk VII, but it was very rare, as it had reliability problems, and was
replaced by a redesign called the Mk VIII(8). The Mk VII(7) used three
along with a slew of cold cathode thyratrons. The Mk VIII dispensed with
two of
the dekatrons, leaving only one dekatron which was used to scan the
The counters that performed the counting operations of both machines were
made with 10 thyratron ring counters. The ring counters were directly
to the Nixie tubes, and, in fact, the Nixie tubes were actually an active
part of
the sequencing of the ring counters. The Nixies were specially designed
with the
digit cathodes in a specific order to facilitate the jumping of the ring
from one state to another.

The are no heaters used in the thyratron tubes that are present in the Anita
Mk 7, Mk 8, or
Mk 9 calculators.

You can see inside an Mk 8 by going to

Rick Bensene
The Old Calculator Web Museum

> > I've looked recently inside an Anita MK IV calculator and a doubt that
> > would want to use that many tubes with heaters in that small a case...
> Most thyratrons have filaments anyway. The only one that leaps to mind
> that doesn't is the Americal 0A4G, and it is an octal. I am sure there
> are some other obscure types, but my Tube Lore is buried somewhere. The
> favorites 2D21 and 5696, have filaments (they are miniatures).
> For something as simple as a calculator, you could get away with a couple
> hundred subminiature tubes, and still be able to plug it into a standard
> wall outlet, and still have it small enough to sit on a desk. The KWR-37
> crypto box from the 1950s has something like 500 submini dual triodes, yet
> still is only a few cubic feet.
> Of course, no one in there right mind would pay for such a calculator.
> > The thyratons it uses are cold cathode and quite small. It also uses 1
> > Decatron tube...
> Interesting. I would think there would be more Decatrons than that.
> William Donzelli
Received on Fri Feb 28 2003 - 17:04:00 GMT

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