"Bob Noel" wrote in message news:ihatessppaamm-

I haven't had an opportunity to check my TCAS sources. But
I seem to remember the TCAS II unit having some interface
with the Radar Altimeter. Also, I'm pretty sure that a GPWS
(or TAWS) warning/alert/whateveritiscalled takes priority over
an RA.

Note that a radar altimeter isn't normally used above 2500' agl.

I found some TCAS II block diagrams and it is connected to both
the pressure alt and the radar altimeter. There appears to be
a shift in the RA behavior at 1700' AGL which would jive with your
2500' threshold