computer graphics in the 1950s

[Tony Duell]

> > There was a color vector display technology that didn't use a shadow 
> > mask or phosphor dots, but it was very uncommon.  It used two layers of 
> > phosphor with different activation energies, and the high-voltage supply 
> > was actually switched between two voltages.  The lower voltage only 
> > activated one phosphor, but the higer voltage activated both, so two 
> > different colors were available.  This was used in the DEC VR20 monitor, 
> > of which few units were believed to have been sold.
> 
> I haev an HP1350 'graphics translator' here -- it's an HPIB input vector 
> display generator. The manual mentions an HP colour vector monitor for 
> this unit, which would appear to work as you described, alas I've never 
> seen one (I have the HP1311 monochrome monitor only). I cna dig out the 
> model number if anyone wants to look for one.

I have looked in the HP1350 manual, the monitor in question is the 
HP1338. I can find no mention of it on the web at all, alas. 

According to the HP1350 manual, it had a 2-bit colour selection input, 
providing 3 colours (the 4th state repeated one of the other colours). 
Said colours were red, yellow, and green. I have no idea how it worked, 
whether it was a shaddowmask CRT (but if it was, why not also have blue?) 
or one with difference energy phosphors. 

-tony