  The current in response to a rectangular pulsed bias potential is calculated
exactly for a special point in the parameter space of the nonequilibrium Kondo
model. Our simple analytical solution shows the all essential features
predicted by the noncrossing approximation, including a hierarchy of time
scales for the rise, saturation, and fall-off of the current; current
oscillations with a frequency of eV/hbar; and the instantaneous reversal of the
fall-off current for certain pulse lengths. Rich interference patterns are
found for a nonzero magnetic field (either dc or pulsed), with several
underlying time scales. These features should be observable in ultra small
quantum dots.
