Antonio I0JX wrote:
In the vacuum tube era, a tube (e.g. 6V6) was usually produced by several
manufacturers. I am not sure of how things actually went, but I would say
that a manufacturer initially designed the tube and put it on the market,
and subsequently other manufacturers "copied" the tube. But how did they
actually copy it? Just by reverse engineering (e.g. measuring dimensions and
distances among electrodes)? Or instead the original manufacturer published
the detailed tube design so allowing others to produce it? The first option
seems more likely to me, as manufacturers should have little interest in
helping others to replicate a tube.

The same way it happens today in the solid state era! One company introduces
an IC, and a second company pays a licensing fee to second source the design.
A third company makes a "compatible" device through reverse-engineering and
a fourth company makes an "improved" version with additional features which
meets the specifications on the datasheet but may have something totally
different than the original inside the package.

Also, just because a company is selling it doesn't mean they made it. Most
of the compactron types were only made by GE... they were sold by a lot of
different companies but even the Sylvania ones came from the GE factory.

The same question applies to solid-state devices, but in that case I would
expect that reproducing a device having (almost) the same characteristics
through a reverse engineering process would be very hard, if not
impoossible.

Depends on the device. Just about everybody making a 2N2222 is using a
die that looks the same; they are all copying one another. Intel made
the 8080, but then Zilog made a compatible microprocessor, the Z-80,
that was totally different inside. It wasn't a copy at all. Much of it
has to do with the complexity of the device. The 2N2222 is not so hard to
reverse-engineer, whereas the latest Intel microprocessor is.

Does any one know how things go in practice?

Much worse now that we have so much production in China where intellectual
property regulations are lax at best. Now you can contract a fab line to
make an IC for you, and then after the run is finished they keep an extra
set of masks so they can keep making the part for your competititors...
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."