  The current-voltage ($I$-$V$) characteristics of break junctions of
polycrystalline La$_{1.85}$Sr$_{0.15}$CuO$_4$,
Y$_{0.75}$Lu$_{0.25}$Ba$_2$Cu$_3$O$_{7-\delta}$,
Bi$_{1.8}$Pb$_{0.3}$Sr$_{1.9}$Ca$_2$Cu$_3$O$_x$ and composite
YBa$_2$Cu$_3$O$_{7-\delta}$ + Ag are investigated. The experimental $I$-$V$
curves exhibit the specific peculiarities of
superconductor/normal-metal/superconductor junctions. The relation between an
$I$-$V$ characteristic of network of weak links and $I$-$V$ dependencies of
typical weak links is suggested to describe the experimental data. The $I$-$V$
curves of typical weak links are calculated by the K\"{u}mmel - Gunsenheimer -
Nicolsky model considering the multiple Andreev reflections.
