  We apply the NLTE atmosphere code FASTWIND to perform a spectroscopic study
of a small sample of Galactic B-supergiants from B0 to B9. By means of the
resulting data and incorporating additional datasets from alternative studies,
we investigate the properties of OB-supergiants and compare our findings with
theoretical predictions. As a result we find that due to the combined effects
of line- and wind-blanketing, the temperature scale of Galactic B-supergiants
needs to be revised downwards, by 10 to 20 percent, the latter value being
appropriate for stronger winds. In fair accordance with recent results, our
sample furthermore indicates a gradual decrease in wind terminal velocities
over the bi-stability region, where the limits of this region are located at
lower temperatures than the predicted ones. Introducing a distance-independent
quantity Q' related to wind-strength, we also show that this quantity is a well
defined, monotonically increasing function of Teff outside this region. Inside
and from hot to cool, the mass loss rate changes by a factor (in between 0.4
and 2.5) which is (much) smaller than the predicted factor of 5. All this
indicates that the decrease in wind terminal velocity over the bi-stability
region is not over-compensated by an increase of mass loss rate, as frequently
argued (provided the wind-clumping properties on both sides of this region do
not differ substantially).
