Abstract: An electrolytic process generates erasable pictures on a solid electrolyte substrate to electrically record data without consumption of energy. The substrate is electrically erasable at will, and then is capable to record data again, and usable as well in telecopy receiver apparatus as display screen. The recording may be made by using an unwearable electrode made of a metal and using a low voltage power supply, for instance under 10V, and a small current. The substrate is substantially unsensitive to ambient light. An electrolytic process locally generates an optical absorption at the surface of an electric conductive layer connected to an anode. The layer has an optically diffusing powder and a metal compound, the amount of which is relatively small. The optical absorption is produced at the contact point between a supplied cathode and the surface by means of a reduction of the metal compound.