A display (100) primarily intended for use on an external surface of a building comprises a weatherproof housing (310, 340); a bistable electro-optic medium (326) enclosed within and visible through the housing; an electrode (324, 330) enclosed within the weatherproof housing and arranged to drive the electro-optic medium; a power generating means (504) enclosed within the weatherproof housing; data receiving means (508) enclosed within the weatherproof housing and arranged to receive data wirelessly from a source outside the weatherproof housing; and display drive means (510) arranged to receive data from the data receiving means and power from the power generating means, and to control the potential of the electrode.