  We present results of simulations of transitions in planar arrays of
superheated superconducting granules (PASS) immersed in an external magnetic
field parallel to the system. Analysis of the behaviour of the system when the
external field is slowly increased from zero shows the existence of an interval
of external fields for which no transitions are produced. This gap is found to
be a consequence of ordering induced by transitions. However, this ordering is
different for diluted and for concentrated systems. Avalanches of different
sizes with distributions depending on concentration are observed.
