and an uneven row on alternating vce after each row the single voltage vcb is formed from a pedestal of duration t 1 having a value equal to the voltage of the counterelectrode vce i e 0 in the case a and vc in case b and a linear ramp of duration t 2 which passes the voltage from the preceding value to a value differing from vce by a quantity vc i e which reaches vc in case a and 0 in case b the total duration t 1 t 2 is equal to the control duration t l of a row in fig7 to 11 it is assumed that the polarity alternation takes place after each frame fig1 illustrates the case where the alternation takes place after each row fig7 shows in part a the single voltage vcb during various row scans it still being assumed that a frame is formed from five row scans and in part b the counter electrode voltage vce and its alternation at each frame thus the voltage ramp vcb has a positive slope for one frame which corresponds to the signal of fig6 a and a negative slope for the following frame which corresponds to the signal of fig6 b on now considering a particular column it is necessary to determine the interval during which said single voltage will be applied to the column this time is determined by control circuits which as will be shown hereinafter can be transistors brought into the on or off state in fig8 to 11 these states are represented in part b by an on state ep and an off state eb interest is attached in fig8 to a point located on the.