Originally Posted by Bloggs
TCAS uses the transponder system. Transponder off? TCAS inop.
I was a bit flippant there. Here's what the 717 displays:
Transponder Setting/TCAS Status display
STBY / TCAS Off
Alt Off / TCAS Off
Alt On / TCAS STBY
TA / TA ONLY
TA/RA / Nothing