  Transmission measurements through three-port microwave graphs are performed
in a symmetric setting, in analogy to three-terminal voltage drop devices with
orthogonal, unitary, and symplectic symmetry. The terminal used as a probe is
symmetrically located between two chaotic graphs, each graph is connected to
one port, the input and the output, respectively. The analysis of the
experimental data exhibit the weak localization and antilocalization phenomena
in a clear fashion. We find a good agreement with theoretical predictions,
provided that the effect of dissipation and imperfect coupling to the ports are
taken into account.
