Duane Percox wrote:
>
> This thread reminds me of an interesting project
> I was involved in during my college days.
>
> It was a trinary logic computer. It had 3
> states: off, on, maybe off/on.

There are real bus architectures that way, zero, one, "high-z".

It isn't tri-state, but I very well recall and up until several years
ago had a little puzzle that was round, had a clear plastic cover, and
eight black plastic "wedges" that allowed them to be "in" or "out".
Inside the puzzle were ingenious little circles (tumblers) which moved
along with the wedges, unlocking some wedges and locking others in place
(each wedge had a vertical pin that would slide the wedge in or out).

The object was to start fully closed, and the goal was to open every
wedge.

I don't remember the exact circuit from my hardware days, but it was
essentially a flip-flop only counter starting at 0-0-0-0-0-0-0-0.  For
each new "increment" you could only change 1 bit, so the solution began
as (0=wedge in, 1=wedge out):

   (0-7)     (8-15)
  00000000  10110000
  10000000  11110000
  11000000  01110000
  01000000  01010000
  01100000  11010000
  11100000  10010000
  10100000  00010000
  00100000  00011000
  00110000  10011000 (etc)

If you just "toggle states" the order is more obvious by watching the
number of the wedge to toggle: 1-2-1-3-1-2-1-4-1-2-1-3-1-2-1-5. etc.

Any junk, urr, umm, treasure collectors have one of these beasts?  It
appeared about 25 years ago (+/- 5).

Jeff

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