  We consider a particle in the over-damped regime at zero temperature under
the influence of a sawtooth potential and of a noisy force, which is correlated
in time. A current occurs, even if the mean of the noisy force vanishes. We
calculate the stationary probability distribution and the stationary current.
We discuss, how these items depend on the characteristic parameters of the
underlying stochastic process. A formal expansion of the current around the
white-noise limit not always gives the correct asymptotic behaviour. We improve
the expansion for some simple but representative cases.
