Lines i_lim(e),i_min(e),i_max(e) defined in Sect. 3.1. The numerical values are derived for PSR1931+24. The shaded area corresponds to the set of parameters i and e that allow both on and off modes. The vertical line at e = e_max (Eq. (7)) limits the domain where on an off regimes may occur. These exist in the shaded area. Below the curve i = i_lim(e) Eq. (B.2) no additional condition applies. Parameters allowing on an off regimes in the region i > i_lim(e) require i < i_max(e), the latter is defined in the text following Eq. (B.5). There is a perfect continuity between these two domains.