22 Apr
1999
22 Apr
'99
3:48 p.m.
On Thu, 22 Apr 1999 CLASSICCMP(a)trailing-edge.com wrote:
Neon lamps - when powered by DC - have a nice memory
property: They
take about 90VDC to light up, but after they light up they'll stay on
until the voltage drops below 60VDC or so. Only problems are:
1. The thresholds can vary greatly from unit to unit.
2. The thresholds will vary depending on ambient light, as well.
Property 2 above can be used to build oscillators out of pairs
of neons, as a matter of fact...
There was a funny story related to that issue (#2) at one of the Computer
Museum History Center's computer history lectures a few months ago. I
hope my attribution is correct, but I seem to remember it was the Johnniac
computer that used neon memory. One day it started malfunctioning. To
make a long story short, the cleaning woman used to come into the computer
room where the Johnniac was, vacuum about, then turn off the lights when
she was done before she left the room. The computer would start
malfunctioning once the lights went out. It took the operators and
engineers a while to figure it all out :)
Sellam Alternate e-mail: dastar(a)siconic.com
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