  Supermassive black holes may be described by their mass and spin. When
supermassive black holes are active, the activity provides a probe of the state
of the black hole system. The spin of a hole can be estimated when the black
hole mass and beam power of the source are known for sources with powerful
outflows. Seventy-five sources for which both the black hole mass and beam
power could be obtained are identified and used to obtain estimates of black
hole spins. The 75 supermassive black holes studied include 52 FRII radio
galaxies and 23 FRII radio loud quasars with redshifts ranging from about zero
to two. The new values are combined with those obtained previously for 19 FRII
radio galaxies, 7 FRII radio loud quasars, and 29 radio sources associated with
CD galaxies to form samples of 71 FRII radio galaxies, 30 FRII quasars, and a
total sample of 130 spin values; all of the sources are associated with massive
elliptical galaxies. The new values obtained are similar to those obtained
earlier at similar redshift, and range from about 0.1 to 1 for FRII sources.
The overall results are consistent with those obtained previously: the spins
tend to decrease with decreasing redshift for the FRII sources studied. There
is a hint that the range of values of black hole spin at a given redshift is
larger for FRII quasars than for FRII radio galaxies. There is no indication of
a strong correlation between supermassive black hole mass and spin for the
supermassive black holes studied here. The relation between beam power and
black hole mass is obtained and used as a diagnostic of the outflows and the
dependence of the magnetic field strength on black hole mass.
