The network method has been used to analyse the conditions of linearity of the voltage-current relationship in symmetric and asymmetric thin-layer cells with type I electrodes. A network model for the Nernst-Planck and Poisson equations describing the ionic transport through the electrolyte solution and for the Butler-Volmer equations describing the interfacial kinetics in these systems has been proposed. With this model and the electric circuit simulation program PSPICE(TM), a decomposition into Fourier components of the electric current-time response, which follows the application of a sinusoidal-shaped potential difference between the electrodes, is obtained. The results reveal a considerable influence of the type of contacts on the amplitude of the different harmonics.