[Boatanchors] Tube data

[J. Forster]

telegrapher at att.net wrote:

> The 6919 is a "high Perveance twin Diode" for use in Computers.  O,
> what's "High Perveance" mean?

Google finds:

                Perveance is related to conductance. It depends on cathode
surface area, on its temperature and on
                the electron emitting properties of the cathode materials.
Doubling perveance is equivalent to placing
                two identical tubes in parallel.

> The other, a 6687/E-91H is a dual control heptode used in computers.
> Since tube based computers were before my time, what actually were these
> two used for?

Making gates or Flip-Flops.

-John