  We present results from Chandra and XMM-Newton spectroscopic observations of
the nuclei of z<0.5 radio galaxies and quasars from the 3CRR catalog, and
examine in detail the dichotomy in the properties of low- and high-excitation
radio galaxies. The X-ray spectra of low-excitation sources (those with weak or
absent optical emission lines) are dominated by unabsorbed emission from a
parsec-scale jet, with no contribution from accretion-related emission. These
sources show no evidence for an obscuring torus, and are likely to accrete in a
radiatively inefficient manner. High-excitation sources (those with prominent
optical emission lines), on the other hand, show a significant contribution
from a radiatively efficient accretion disk, which is heavily absorbed in the
X-ray when they are oriented close to edge-on with respect to the observer.
However, the low-excitation/high-excitation division does not correspond to the
FRI/FRII division: thus the Fanaroff-Riley dichotomy remains a consequence of
the interaction between the jet and the hot-gas environment through which it
propagates. Finally, we suggest that accretion of the hot phase of the IGM is
sufficient to power all low-excitation radio sources, while high-excitation
sources require an additional contribution from cold gas that in turn forms the
cold disk and torus. This model explains a number of properties of the
radio-loud active galaxy population, and has important implications for AGN
feedback mechanisms.
