MOTM

Hi all,

could someone try to explain in layman's terms what it means 
when an input is either AC or DC coupled?

I know it means it assumes either an AC or DC signal. But 
what if I feed it the other type of signal?

And a related question: what is the definitions of an AC and 
DC signal, in modular context? For example, when I an EG 
ouputs a through-zero DC signal, isn't that actually an AC 
signal?

Confused...

- Robert