Two arrays of main X and Y electrodes are juxtaposed with two arrays of auxiliary electrodes in two parallel plane respectively. Two half illumination or extinction pulses less in magnitude than a discharge voltage across the opposite arrays and opposite in polarity are applied to selected ones of the X and Y electrodes to initiate or terminate an electric discharge or discharges across them. A pulse train including positive pulses alternating negative pulses is applied across the arrays of auxiliary electrodes to be discharged across those auxiliary electrodes juxtaposed with the selected X and Y electrodes upon each inversion of the pulses polarity after the first discharge.