We consider the implications of the two-pocket Fermi surface for macroscopic quantum phenomena in cuprates. Superconductivity in this system can be described in terms of two coupled condensates. It results in a collective excitation corresponding to the relative phase oscillation - a phason. The energy of the phason is smaller than the maximum gap on the Fermi surface. We discuss the possibility of searching for this collective excitation in the dynamic resistance of a superconducting interference device (SQUID).