Current / voltage detection

[kenah]

What would output a digital signal to detecting the presence of voltage / current even if it were to be high?

[KMoffett]

So you want an output to be ~0V when the input voltage or current is either 0V or 0mA? And the output to be +5V when the input voltage or current is "any level" greater than 0V or 0mA? What's the realistic maximum voltage or current? Are you talking AC or DC? And...since it might help us to know...what's the purpose of this project?

Ken