On 2012-02-20, Michael A. Terrell wrote:

"DoN. Nichols" wrote:

On 2012-02-19, Michael A. Terrell wrote:

"DoN. Nichols" wrote:

[ ... ]

Non-Linear System's digital voltmeters used a series of stepper motors
to implement a Kelvi-Varley divider. Four digits, IIRC. Really noisy
with the sound-deadening cover off for test or repair. :-)


Today, you could use a couple rectangular LEDs per segment. You could
even change the color for out of range conditions.

Yes, those would be pretty good. Of course, they would be
*much* more expensive to make than the off-the-shelf 7-segment LED
readouts. (There was a *lot* of precision machining in that NLS readout
assembly. :-)


Which would be easy with a CNC machine. Can you imagine the problems
NCR had making their mechanical cash registers without CNC?

Indeed -- lots of custom fixturing. Actually, I think that the
frame for all the Plexiglas (or Lucite) panels was likely made with a
horizontal mill with a stack of cutters on it cutting all the guide
slots in the sides in a single pass, then assembled to make the overall
frame.

[ ... ]

Indeed so, as do I. Lovely little things. What would be nice
would be to get LEDs in the same package -- ideally with a built-in
bridge rectifier to make them happy with AC power. :-) Should last a
*lot* longer than the same lamps in a vibrating environment like an
aircraft cockpit.


LED replacements have been available for over 20 years, but they are
even more expensive than the lamps they replace.

Not when you count the cost of replacing them frequently, or
having a crucial indicator lamp burn out in the cockpit. (Of
course, they typically had two or three lamps per indicator, so you get
some warning when one lamp burns out.

Enjoy,
DoN.

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