Since the pioneering work by Osteryoung et al., J. Electroanal. Chem. 222 (1987) 69, the discussion about the equivalence of staircase and linear scan voltammograms is based on the 'Abelian' or 'non-Abelian' feature of the integral equation used for modelling the voltammetric response of redox systems. In practice, further investigation is required for prediction of the optimal value of current sampling parameter (gamma(opt)) that guarantees the equivalence of voltammetric and staircase voltammetric data. This first article focuses on reversible electron transfer reactions involving soluble species. The discussion is based on integral-equation-based models and the use of local/global criteria for the comparison of staircase and linear scan voltammograms. Main results in the article and the Supporting information joined should concern the dependence of gamma(opt) on the electrode potential, the potential step amplitude of staircase signal, the reaction scheme, and the mass transport process involved.