Pulse-sequence polarization display showing three distinct behaviours: the normal mode (pulses 1960–1977 and 2015–2050), abnormal (1998 to 2010) and flare-normal mode (1978–1994) of the 2003 July 21 observation. The total power I, fractional linear L/I, PA χ and fractional circular polarization V/I are colour-coded in each of four columns according to their respective scales at the left of the diagram. Core-component emission is virtually absent in the quiet-normal mode, the conal components exhibit regular modulation with a P₃ of 2.8P₁, marked by a cyclic alternation of PPM (−10°, purple) and SPM (+80°, chartreuse) power on the outer profile edges. The core component ‘flares’ in the abnormal mode to almost continuous brightness, the conal modulation ceases and SPM power predominates on the profile edges. The flare-normal mode can be distinguished within the total-power column by the presence of core activity together with something of the normal conal modulation. It also exhibits distinct linear PA and circular characteristics as compared with abnormal and quiet-normal intervals. Note the frequent presence of RH circular polarization in both flare-normal and abnormal sequences, but the two modes differ markedly in their PA signatures, especially around the core longitude. The flare-normal-mode PS here is longer than most and appears to exhibit a longer P₃ than in the proceeding quiet-normal interval. The PS between pulses 1950 and 1958 perhaps falls somewhere between the flare-normal and abnormal modes as it exhibits both the frequent core activity and conal modulation of the former, but shows a PA traverse more like the latter. Finally, we see numerous individual pulses such as 1997 and 2012 where very partial emission within the pulse window is none the less polarized at an appropriate PA for that longitude. Both the background noise level and interference level of these observations is exceptionally low with the latter effectively disappearing into the lowest intensity white portion of the I colour scale.