Why time limit is minus value to po

[Htet_Khant]

Why time limit is minus value to positive value in communication system????
eg.minus infinity to infinity
I don't get the reason.
Someone explain me please.

 

[IRstuff]

Huh? You have a time machine that runs time backwards?

Otherwise, I suggest you read up on Fourier analysis, I guess.

Your question is otherwise cryptic, given the lack of context.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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