  We present the results from a study of wide profile pulsars using high
sensitivity multifrequency observations with the GMRT. Since the line of sight
samples a large region of the polar cap in case of the wide profile pulsars,
presence of simultaneous multiple drift regions is quite probable (as seen in
PSR B0826-34 and PSR B0818-41). We solve the aliasing problem of PSR B0818-41
using the observed phase relationship of the drift regions, and determine its
pattern rotation period P4 to be ~ 10s, which makes it the fastest known
carousel. We find that, for all the pulsars showing drifting in multiple rings
of emission, the drift pattern from the rings are phase locked. This can
constraint the theoretical models of pulsar emission as it favors a pan
magnetospeheric radiation mechanism.
