Okay, where goes the limits being unskilled and being completely retarded?
Not satisfied? I just tried to help.
If you know wikipedia, why didn't you tried to search yourself then?
You can make the resistor values so that the schmittrigger takes the floating voltage window as the hysteresis voltage. That's the answer. It might work or it might not work.
And what's the talking about some germans? Oh, I kinda guess it. The word schmitt-trigger is german. Sure it sounds like, but any opamps from any vendors should be good enough to make a schmitt-trigger outa. Better blame all other people that couldn't give it another name?
And the voltage diviter should be put in front of the schmittrigger, dividing the signal. As the output goes flowing (your output), any input impedance would cause voltage being 0V.
No - fuzzy responce = fuzzy thinking. You need two opamps (really think we can forgot about that german thing now). One that compares voltages slightly above 0V and the other one slightly below 0V.
Then connect the two outputs from the opamps into an AND gate. That should work.