It would be pretty-much impossible to determine from only the result what preprocessing might have been done other than, perhaps, being able to tell about some high/low/bandpass filtering (and even that would be moderately iffy depending upon just what the signal characteristics are).
Your first step is to find out from the manufacturer of the input devices what they document as to what their equipment provides as far as outputs. And, of course, what software you're using to collect the data beyond just a straight A/D converter--if they're writing some text or other data files, there's that piece of software in the middle.
