# BreakPoint

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## Re: Invert three signals with only two NOT gates

@Ben wrote:

Forgive me if I am wrong but the answer using just two "NOT" and a mix of ANDs and ORs has not been answered?

No, it was not answered yet here. And the solution does exists.

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## Re: Invert three signals with only two NOT gates

@Andrey_Dmitriev wrote:

[...]  You can easily found an answer in the Internet, [...]

It was only easy because of the way you titled this thread.  I think the solution was generated by an "infinite monkeys" VI generator, as no human could have come up with the solution.

Jim
You're entirely bonkers. But I'll tell you a secret. All the best people are. ~ Alice
For he does not know what will happen; So who can tell him when it will occur? Eccl. 8:7

Message 12 of 17
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## Re: Invert three signals with only two NOT gates

@jcarmody wrote:

I think the solution was generated by an "infinite monkeys" VI generator, as no human could have come up with the solution.

Yeah, the fun of this question that it sounds simple initially, but quite complicated to implement. I will put solution under spoiler.

Spoiler

I will ask this question on every interview, where I involved time to time. The person who will solve it within half an hour will be hired immediately.

Message 13 of 17
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## Re: Invert three signals with only two NOT gates

I found two solutions; I didn't figure them out myself.  Putting them in a Spoiler tag wouldn't matter, but I'll go along.  I'm convinced that deriving the logic is inconceivable and you'll never hire anyone immediately!  Did you really figure it out yourself?  Color me impressed!

Spoiler

Jim
You're entirely bonkers. But I'll tell you a secret. All the best people are. ~ Alice
For he does not know what will happen; So who can tell him when it will occur? Eccl. 8:7

Message 14 of 17
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## Re: Invert three signals with only two NOT gates

I don't understand you "hardware guys".

Just put the NOT into a non-reentrant subVI and place it as many times as you want. Only one instance! 😄 😮

LabVIEW Champion. It all comes together in GCentral
What does "Engineering Redefined" mean??
Message 15 of 17
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## Re: Invert three signals with only two NOT gates

@altenbach wrote:

I don't understand you "hardware guys".

Just put the NOT into a non-reentrant subVI and place it as many times as you want. Only one instance! 😄 😮

The hardware solution will be faster than the software approach and like NXG "no programming required".

I have not looked at the spoilers (yet) but I did ponder the challenge a bit in the hotel room the night before last. The truth table show that if we look at the input as a number "X" the output is "X-7". So a subtraction of "7" OR adding the (was it 2's?) 2s-compliment of seven would give results. It would require 5 half-adders that did not use an "inverter".

Did not go any farther than that before it was time to go to bed.

Ben

Retired Senior Automation Systems Architect with Data Science Automation LabVIEW Champion Knight of NI and Prepper LinkedIn Profile YouTube Channel
Message 16 of 17
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## Re: Invert three signals with only two NOT gates

Back in High School the Math dept. head taught the calculus class.  It included a quarter of Logic.  He could not find a text he liked so...(logically) wrote his own.  Anyone who has passed that course would remember "Tautology 4".

"Should be" isn't "Is" -Jay
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