Thanks very much - this was the perfect answer!

Tim




in article , default at
wrote on 16/10/05 15:36:

On Sun, 16 Oct 2005 12:20:32 +0000 (UTC), Tim Rogers
wrote:

Hi I'm wondering if any of the members here can help.

I'm trying to find out if there is a technical or trade name for the digital
countdown instrument seen in the old test videos counting the final seconds
to a detonation. I don't mean the whole piece of apparatus but rather the
small round indicator that counted down the seconds . The numbers seemed to
be made of little dots and were a red/orange colour. Was it an early LED of
some kind?

Thanks for your help,

Tim

They used a variety of counters in the old days. The classic was a
round neon device with a center electrode and ten digit dots around
the periphery in a end looking vacuum (neon) tube. The tubes
functioned as both a counter and display. They were called Dekatrons.

They are collector's items but still being sold.

The also used neon bulbs in a "ring counter" that would sequentially
light a ring of individual neon's.

Check these out:

or search for Dekatron, Numitron, Nixie

http://www.wps.com/projects/decimal-tubes/index.html
http://www.sphere.bc.ca/test/nixies2.html
http://www.technology.niagarac.on.ca...sele/Nixie.htm

They didn't have LED's until the late 60's or so. The atomic test was
in the 40's