> I thought, at first, some dirt or debris had gotten stuck there, but > on closer look I saw something black below the keys that seemed to be > stuck. I pulled a key cap off and found a U shaped piece of black > plastic that was put there on purpose to prevent you from depressing > the key.
> The question came to mind; "What sort of application would be so > crude that you would have to prevent the user from depressing certain > keys?" I saw this in at least two applications: 1. The Service Merchandise chain (https://en.wikipedia.org/wiki/Service_Merchandise) used serial terminals for their in-showroom catalog ordering. Some keys were blocked somehow, though I never peeled up key caps to see how. :) I want to say that backspace was one of the blocked keys, the aggravation of which is probably why I remember this. 2. CLSI library systems (LIBS100 on PDP-11). Ours here had ADM-3A (iirc) terminals with the break key blocked, iirc, though there were plenty of other ways to discombobulate the thing inadvertently. It was also available via dialup from keyboards that were not so modified. I once heated up a paper clip to read hot and shoved it through the stem of a TVI-925's SEND key, which was used for block mode functions, and caused the terminal to vomit screen contents back to the host. Unwanted presses of course produced a heck of a mess. (Older versions of our application ran in block mode, but you could always hit ESC-S to send the screen, and it was unfortunately easy, at least for me, to thwack SEND by mistake.) De
