R. Martin wrote:

> I didn't totaly follow the argument at the time it was of the nature
> of a law of physics or mathemetics (or death and taxes). It was
> calculated that the memory systems would lock up about once every
> ten years. Nobody confirmed this experimentaly.

What's wrong with 10 SCR's? 48 cents each for TO92 sensitive gate 0.8
amp SCR's from Mouser.  20 resistors so the first switch pressed causes
it's SCR to conduct and light it's light but pulls up the common side of
all the bulbs (resistor from bulb common to ground) so subsequent switch
closures will not turn on the gates of any of the other SCR's.  $5.00
plus switches and bulbs.  Since there is no clocking of logic involved,
it will work correctly every time plus drive healthy light bulbs.

Or how about 10 D flip flops with 2 input And gates on the D input.  One
input of each and gate goes to a switch. The not Q outputs are all or'ed
and the output of the 10 input Or gate (actually an And gate) goes to
all the other inputs of the And gates on the D inputs.  The Flip flops
are clocked together at a high rate.

If any switch is pressed, a high is clocked in and that flip flop Q
output goes high lighting its light.  At the same time that flip flop's
not Q goes low.  Now that one of inputs to the 10 input And gate
(inverted input, inverted output Or gate) the 10 input And gate output
will go low bringing one input of all the 2 input And gates low thus
disabling all inputs.

The first switch bounce that get clocked in is the winner.  If the #1
contestant's switch bounces low when the clock occurs and #2's switch
happens to be high on the next clock and #1 is low again, the machine
makes a wrong call.  A tie would also be possible juat from propagation
delay. Switch bounce is in milliseconds, logic can be clocked in Mhz.
Shouldn't be a problem more than once in ten years.

Same with the SCR's. SCR's wouldn't conduct and lockout other
contestants instantaneously.  A tie would be the only failure mode with
the SCR's.  If it's that close, maybe it is a tie.  As long as this game
isn't a matter of life or death.  And heck, there's millionaires that
don't pay taxes.

It's at least difficult to synchronously sample inputs with a PIC.

Don