  A possible scenario for an ac Josephson effect initiated by the flow of
dislocations through a mechanically loaded but electrically unbiased
superconductor is proposed. The characteristic voltages due to the motion of
dislocations in loaded (under the applied stress of 10^7N/m^2) YBCO crystals
are estimated to be of the order of a few picovolts (which corresponds to the
Josephson frequency of 10 kHz).
