  In DC transport through mesoscopic S-N-S junctions, it is known that the
Josephson coupling decreases exponentially with increasing temperature, but the
phase dependence of the conductance persists to much higher temperatures and
decreases only as 1/T. It is pointed out here that, despite the fact that such
a phase-dependent conductance does bring about an AC current for a pure DC
voltage, it cannot, by itself, lead to the formation of Shapiro steps.
