An electro-optic display comprises a bistable electro-optic medium, a plurality
of pixel electrodes, with associated non-linear elements, and a common electrode,
disposed on opposed sides of the electro-optic medium. The display has a writing
mode, in which at least two different voltages are applied to different pixel electrodes,
and a non-writing mode in which the voltages applied to the pixel electrodes are
controlled so that any image previously written on the electro-optic medium is
substantially maintained. The display is arranged to apply to the common electrode
a first voltage when the display is in its writing mode and a second voltage, different
from the first voltage, when the display is in its non-writing mode.