Two-terminal devices generally work as "leaky resonators" in coherent transport, which mixes up the quantum phase information from all parts of the devices, e.g., quantum dots (QDs) embedded in them. With the aid of appropriate theoretical modeling, however, we can extract important information on the phase from the total conductance. As typical examples, we present here experiments in a side-coupled QD, and a QD embedded in an Aharonov-Bohm (AB) ring. In the former, kinetic degrees of freedoms transverse and longitudinal to a quantum wire give rise to dramatic change in the interference effect. In the latter, "phase shift locking to π/2" appears as a plateau structure in the conductance. Specialized theoretical models give reasonable explanations to these effects, bringing important information on the phase of the electron wavefunctions in the QDs.