Abstract: A method of control for a metal halide electrolytic display cell consists in passing a control current through the cell in a first direction during periods of erasure and in the opposite direction during writing periods, a zero control current being maintained during periods of holding in the erased state and during periods of holding in the written state. A low leakage current is superimposed on the control current and passes through the cell in the first direction, at least during the periods of holding in the erased state.

Abstract: The electrolytic display cell comprises a plurality of electrodes having suitable shapes for character display, a counter-electrode and an electrolyte. A negative voltage is applied to one of the electrodes for writing on said electrode and a positive voltage is applied for erasure. On completion of erasure, the voltage between electrode and counter-electrode has a tendency to rise to a threshold value corresponding to a parasitic reaction. The end of the erasure pulses is determined by the instant at which the electrode--counter-electrode voltage rises to the threshold voltage corresponding to the production of a parasitic reaction.