  It is shown that the effect of hole-burning under conditions of coherent
population oscillations as well as the light pulse delay in a saturable
absorber (a modification of the "slow light" effect) can be interpreted, in a
comprehensive way, in terms of {\it intensity spectrum} of the light and {\it
intensity-related susceptibility} of the non-linear medium. The physical
content of these effects is illustrated by a simple electric circuit with a
non-linear resistor which realizes a full analog of the saturable absorber. In
this case the effect of hole-burning in the absorption spectrum of the medium
is converted in to the effect of hole-burning in the frequency dependence of
resistance of the non-linear resistor and the effect of "slow light" -- in to
the effect of "slow current".

Optics