Abstract: A device for digitalizing oscilloscope traces of fast transient signals is rovided in which a plurality of channel electron multipliers are arranged with their cathodes in a coordinate array in the path of a cathode ray beam such that the trace of the beam thereacross energizes those channel electron multipliers in the path of the oscilloscope trace. These multipliers remain energized until their anodes and associated anode circuits are scanned by a digital indexing device in a predetermined raster, synchronized with the oscilloscope, by which the respective coordinates of the energized multipliers are determined and stored in a memory so that the trace can be reproduced at any given time for subsequent analysis.