  A number of previous papers have developed an ion-proton theory of the pulsar
polar cap. The basic equations summarizing this are given here with the results
of sets of model step-to-step calculations of pulse-precursor profiles. The
nature of step-to-step profile variations is described by calculated
phase-resolved modulation indices. The conditions under which nulls are present
in step sequences are analysed. The change of mean null length with
neutron-star surface temperature shows a pathway ending in emission similar to
the Rotating Radio Transients. The model accommodates exceptional pulsars, the
millisecond pulsars (in principle), and the 8.5 s period PSR J2144-3933. These
are considered separately and their emission mechanism discussed in some
detail.
