I think 'copying' would have had legal complications. Usually there was
a licensing arrangement involved. In such a case I imagine the license
holder would have provided detailled information.
Of course Brand B could come up with its on version and get it
registered as their own tube. But the differences between it and Brand
A would have to be sufficient so that they didn't get sued.

RCA was by far the largest license holder and they weren't hesitant to
use their lawyers!

-Bill



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 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.

Does any one know how things go in practice?

73

Tony I0JX
Rome, Italy