Originally Posted by
overthewing
And I don't think TCAS on /transponder off makes you visible to other a/c? Does it?
Like others have said you can't have one without the other. So for you to be able to track an other aircraft using TCAS the other aircraft will be able to see you, as will all the other SSR receivers in the area.
Buy like you said, I'd would be pot luck as to which aircraft you came across, there's no info from TCAS except height and to visually identify the type and the airline you need to be within about ten miles at the most.