Light Pens ...

From: John Allain <allain_at_panix.com>
Date: Tue Jul 17 13:08:53 2001

> I'm curious how that CDC system figured out where I was pointing the light
> pen when I selected a component from the menu, which was at the right
> margin of the screen, and placed it on the screen.
> Those big tubes were storage...

Storage tubes could display in non stored mode. If the write beam was
below a threshold it wouldn't store, and would need to be refreshed.
The 'refreshment' generated the necessary timing signal. Menus were
probably always non-stored for that reason.

John A.
Received on Tue Jul 17 2001 - 13:08:53 BST