The paper discusses a method of reading information from an electroluminescent digital store and describes in detail the operation of a matrix containing 1282digit positions. The method of reading makes use of the non-linear electro-optical property of electroluminescent cells to provide modulation. By applying two sinusoidal excitation voltages, at frequenciesf1andf2respectively, to the selected row and column of an electroluminescent array, only the cell at the intersection will emit light at the difference frequency (f1—f2). This difference frequency may be detected in the photo-current of a photo-multiplier observing the matrix. The information is stored in the form of a punched card or mask placed between the matrix and the photo-multiplier. At a particular operating frequency, the access time and reliability of the store are shown to be a function of the signal/noise ratio at the photo-multiplier output.