Pulse profile of the different modes of PSR B1839−04. These are the combined 2005 data sets (the Q- and B-mode profiles consist of 7605 and 3188 individual pulses, respectively), rebinned with a factor two. The thick solid line and the long-dashed profile show the Q- and B-mode profiles, respectively. The peak flux of the B-mode profile is normalised and the Q-mode profile is scaled accordingly after taking into account the difference in number of pulses. The dotted profile is a scaled-down B-mode profile to aid a comparison between the shapes of the profiles in the two modes. The location of the four profile components are labelled.