  The paper provides a new analysis of this famous five-component ({\bf M})
pulsar. In addition to the star's core-active ``abnormal'' mode, we find two
distinct behaviors within its ``normal'' mode, a ``quiet-normal'' mode with
regular 2.8-period subpulse modulation and little or no core activity, and a
``flare-normal'' mode, where the core is regularly bright and a nearly 4-period
modulation is maintained. The ``flare-normal'' mode appears to be an
intermediate state between the ``quiet normal'' and ``abnormal'' behaviors.
Short 5--15-pulse ``flare-normal''-mode ``bursts'' and ``quiet normal''
intervals alternate with each other quasi-periodically, making a cycle some
60--80 pulses in duration. ``Abnormal''-mode intervals are interspersed within
this overall cycle, usually persisting for only a few pulses, but occasionally
lasting for scores or even many hundreds of pulses. Within subsequences where
the core is exceptionally quiet, the pulsar provides a nearly ``textbook''
example of a central PA sightline traverse--with a PA rate measured to be at
least some 180$\deg/\deg$. On this basis it is shown that the sightline impact
angle $\beta$ must be about 0.25\degr or some 5% of the outer conal beam
radius. The star's core component is found to be incomplete, despite the fact
that the core's full antisymmetric circularly polarized signature is present.
We find that the star's PA traverse is disrupted through the action of
orthogonally polarized linear power in the longitude range of the core
component. This behavior is modeled to show its effect. Finally, the star
provides two well defined fiducial points from which emission-height estimates
can be computed, the respective centers of both the linear PA traverse and the
zero-crossing point of the circular polarization signature.
