  A toy model for jet powers and radio loudness of active galactic nuclei
(AGNs) is proposed based on the coexistence of the Blandford-Znajek (BZ) and
magnetic coupling (MC) processes (CEBZMC) in black hole (BH) accretion disc. It
turns out that both the jet powers and radio-loudness of AGNs are controlled by
more than one physical parameter besides the BH spin. The observed dichotomy
between radio-loud and radio-quiet AGNs is well interpreted by the two
parameters, the BH spin and the power-law index of the variation of the
magnetic field on the disc. Furthermore, we discuss the correlation of jet
powers with radio loudness of AGNs in terms of the two parameters. It is found
that the contours of radio loudness are approximately in accord with those of
jet powers for several 3CR radio sources, implying roughly that the stronger
jet power corresponds to stronger radio loudness. In addition we discuss the
correlation of the jet powers and radio-loudness of AGNs with the position of
the inner edge of an accretion disc. These results imply that the spin paradigm
for radio loudness of AGNs might be modified by a scenario containing more
physical parameters.
