Nice LAB11 brochure.

[Brent Hilpert]

On 2016-May-02, at 2:39 PM, Charles Anthony wrote:
> On Mon, May 2, 2016 at 1:21 PM, Paul Koning <paulkoning at comcast.net> wrote:
>>> On May 2, 2016, at 3:59 PM, Mattis Lind <mattislind at gmail.com> wrote:
>>> 
>>> Yet another nice color brochure.
>>> 
>>> https://dl.dropboxusercontent.com/u/96935524/Datormusuem/lab11.pdf
>>> 
>>> Has anyone seen a VR20 in real? Rather interesting to be able to do a red
>>> and green X/Y screen based on different energy levels. Someone care to
>>> explain how that works?
>> 
>> See https://en.wikipedia.org/wiki/Penetron.  The idea is that there are
>> two layers, and a high voltage beam pokes through the first to activate the
>> second.
>> 
> I'm not sure that the Penetron is what DEC was using; according to
> http://homepage.cs.uiowa.edu/~jones/pdp8/man/vc8e.html:
> 
> "If the CO (color) bit changes because of the value loaded, and if the VC8E
> is equipped to handle this option, a timer will be started to set the DN
> (done) bit after either 300 microseconds (green to red) or 1600
> microseconds (red to green). These delays correspond to the time taken by
> the VR20 display for these color changes."
> 
> According the Penetron wiki page, additional activation energy was provided
> by a "set of fine wires placed behind the screen"; whereas the VC8E
> apparently is setting the color by timing the beam.
> 
> So yes, it seems to be an activation energy phenomenon, but not
> specifically the Penetron technology. My physics fu isn't good enough to
> explain how, but I would guess at some very non-linear phosphorescence
> response.
> 

Might have had to do with the time taken to switch the HV supply (for a Penetron) for the different penetration levels rather than a different phosphor-exciting scheme. Although, is that interface even at the scan level relating directly to the display tube, or at a controller level where it might be an artifact of the controller electronics?