We present an overview of sample-specific transport properties tuned by the superconducting phase difference between two superconductors connected to a disordered 2-dimensional electron gas (2DEG). We demonstrate a crossover from ensemble-averaged to sample-specific resistance oscillations of a T-shaped 2DEG interferometer by increasing the magnetic field. Multi-terminal resistances of a cross-shaped 2DEG interferometer are analyzed in terms of an extended Landauer-Buttiker transport formalism. We show that the extended reciprocity relations hold and that three-terminal resistances become negative. (C) 1998 Elsevier Science B.V. All rights reserved.