  We are interested in the study of the asymptotic behaviour of return times in
small balls for the $T,T^{-1}$-transformation. We exhibit different asymptotic
behaviours (different scaling, different limit point process) depending on the
respective dimensions of the measures of the two underlying dynamical systems.
It behaves either as for the direct product of the underlying systems, or as
for the Z-extension of the driving system (also studied in this article), or as
a more sophisticated process.
