OT: Numitron clocks for sale.

Brent Hilpert hilpert at cs.ubc.ca
Wed Dec 3 20:45:27 CST 2008

Ethan Dicks wrote:
> On Thu, Dec 4, 2008 at 1:31 PM, Bob Shannon <bshannon at tiac.net> wrote:
> > on eBay (Eeek!)
> >
> > eBay item number 200282170878
> >
> > Disclaimer - I am afficiated with this sale.  I designed and built these
> > clocks.
> Very nice.  I don't think I've run across numatrons before.

My understanding of the history is that RCA originally produced a
single-envelope incandescent 7-segment display device they called the
"Numitron" around 1969/70 (RCA Part #: DR2000), in a vacuum-tube style envelope
with a standard 9-pin miniature-tube base.

The Numitron is described and shown in the book "RCA Solid-State Hobby Circuits
Manual" (Printed Sep 1970). (The book includes several circuits, such as a
clock, utilising them. Most of the circuitry is discrete transistor logic,
except for the use of an early 7-seg decoder-driver IC, the CD2500E.) The
Numitron is referred to as being "recently developed". Other phrasing leads one
to believe that "Numitron" was an RCA trademark. I suspect the name went the
way of "Kleenex" and came to be applied more generally as other manuacturers
produced similar devices or copies.

I believe the more-prevalent 7-seg incandescent displays in a
rectangular-envelope form factor (with DIP-IC pins to fit in standard IC
sockets) followed shortly thereafter from other manufacturers. These are often
referred to as "Minitrons", although, again, I believe that was actually one
manufacturer's tradename. There are variations in size and pinout between
different manufacturers in this style as well.

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