  Radio emission from X-ray binary systems (XRBs) has developed in recent years
from being peculiar phenomenon to being recognised as an ubiquitous property of
several classes of XRBs. In this scenario the synchrotron emission is
interpreted as the radiative signature of jet-like outflows, some or all of
which may possess relativistic bulk motion. We have analysed a collection of
quasi-simultaneous radio/X-ray observations of Black Holes in the Low/Hard
X-ray state, finding evidence of a clear correlation between their fluxes over
many orders of magnitude in luminosity. Given that the correlation extends down
to GX 339-4 and V404 Cyg in quiescence, we can confidently assert that even at
accretion rates as low as ~ 10^{-5} dot{m}_{Edd} a powerful jet is being
formed. The normalisation of the correlation is very similar across a sample of
nine sources, implying that it is nearly independent of jet inclination angle.
Remarkably, V 404 Cyg is the second source (after GX 339-4) to show the
correlation S_{radio} proportional to S_{X}^{+0.7} from quiescent level up to
close to the High/Soft state transition. Moreover, assuming the same physics
and accretion:outflow coupling for all of these systems, the simplest
interpretation for the observed scenario is that outflows in Low/Hard state do
not have large bulk Lorentz factors.
