  Nonlinear electrical effects in superconducting S-c-S contacts, including the
spectroscopy of electron-phonon interactions (EPI) in these systems, and the
recovery of the EPI function from experimental data are discussed. The effect
of a magnetic field on the current-voltage characteristics(I-V curves) and
their derivatives for ErNi_2B_2C point contacts (PC) with $d\ge \xi $ (where
$d$ is the diameter of the PC and $\xi $ is the coherence length) is studied.
It is found that in zero magnetic fields and in near-critical fields, when the
size of the superconducting gap can be neglected, the position of the peaks in
$dV/dI$ coincides with the peaks in the Yanson EPI spectra. In low fields the
peaks are shifted toward lower energies and in intermediate fields, the peaks
split. For PC with diameters greater than or on the order of the coherence
length, the relative size of the negative phonon contribution to the excess
current is considerably greater than in ballistic contacts. This leads to
substantial suppression of the high-frequency peaks in the spectra for the
superconducting state. In order to recover the EPI function from these spectra
it is necessary to correct their intensities at high energies. For "dirty"
NbSe_2 and Nb point-contacts with $d\ge \xi $, which have no phonon features in
the second derivative of the I-V curve in the normal state, the EPI can be
reconstructed from the superconducting state.
