Qavion.
Thank you for the replies. I'm still not clear on a couple of things. On my boxes the indications on the MAP are TA ONLY when the transponder is ON in any mode, and TFC when so selected by a seperate switch. In my understanding, with TA ONLY you will get intruder information with TA info only. With TFC displayed you will get RA information. Thus it is possible to have TA/RA selected on the box but with TFC off and the dispaly of TA ONLY. To my mind TA ONLY on the display is what it says.
However, since asking my question, and this addresses your comment about TCAS not knowing about engine failures, I've been told (opinion) that by selecting TA ONLY on the box this sends a signal to other TCAS's that this a/c can not accept RA's. Thus any RA's given to other a/c will take account of the fact that one target can not manoeuvre.
If true, then this bit of kit is smarter than I thought. It's a shame hat so little indepth information is in the AOM's these days.
Indeed, on all our avionics boxes there is no identification of the manufacturer. Thus when any notices are issued you don't know if it applies to your bit of black magic. There is no notice of if the AFDS is Collins, or Rockwell or Honeywell or Dinklydell.