Robert Ehrlich wrote:
The only such system I have heard about is TCAS. As far as I know
this system is not available on gliders, only on big airplanes
carrying passengers or military ones. It should emit hints to the
pilot for avoiding the collision based on altitude information, assuming
that the other aircraft is going to fly at a constant altitude, or
to follow the hint of its own TCAS, and neither is true for a glider.

TCAS/ACAS detects nearby transponder equipped aircraft. In the US and
western Europe, almost all aircraft larger than small twins now have
them. They will provide useful warning of the presence of a nearby mode
C equipped glider, whether or not the glider is flying straight and level.

Marc