TPAS is passive, it does not interrogate, as such much less accurate,
but fraction of the price of TCAS. You can find them under $500.

Ramy

Greg Arnold wrote:
Eric Greenwell wrote:
Ramy wrote:
While you may be detected by ATC on primary without a transponder, you
wouldn't be detected by airliners and other aircrafts carrying TCAS and
will not give traffic resolution.

And you won't be detected by airplanes and gliders using a TPAS instrument.


What is the difference between TCAS and TPAS?