A simulation has been carried out for a potential step experiment at a rectangular shaped geometry where there are four internal electrodes. Two contiguous electrodes form the working electrode and the facing two electrodes form the auxiliary electrode. Both forms of a reversible electrochemical couple are present in solution and an ultimate steady state current is obtained which equals 2 alpha nFADC(b)/d, where the electrode area is 2A, the fraction of the total couple concentration C-b, which is in the oxidized form is alpha and the diffusion coefficient of the couple is taken to be D. d is the width of the cross-section of the rectangle. At short times there is an enhanced current observed due to the recycling of the couple at the corners between the working and auxiliary electrodes.