We investigate a dissipative, deterministic ratchet model in the overdamped
regime driven by a {\it rectangular force}. Extensive numerical calculations
are presented in a diagram depicting the drift velocity as a function of a wide
range of the driving parameter values. We also present some theoretical
considerations which explain some features of the mentioned diagram. In
particular, we proof the existence of regions in the driving parameter space
with bounded particle motion possessing zero current. Moreover, we present an
explicit analytical expression for the drift velocity in the adiabatic limit.Comment: 12 pages, 6 figure