  We develop a theory of pulse conduction in percolation type of materials such
as noncrystalline semiconductors and nano-metal compounds. For short voltage
pulses, the corresponding electric currents are inversely proportional to the
pulse length and exhibit significant nonohmicity due to strong local fields in
resistive regions of the percolation bonds. These fields can trigger local
switching events incrementally changing bond resistances in response to pulse
trains. Our prediction opens a venue to a class of multi-value nonvolatile
memory implementable with a variety of materials.
