Abstract: The device comprises a high speed oscilloscope on the screen of which is formed by scanning a light path representative of the amplitude variation as a function of the time of the signal to be processed. Each point of such path is transformed by an astigmatic optical system into a light segment of constant length projected with off-set on a strip of photodiodes so that each sensor element of the strip receives a light band of a heigth proportional to the ordinate of the corresponding point of the path. An electronic circuit reads the strip after a predetermined number of passages of the signal. The result is displayed on an oscilloscope and stored in a memory after analog-digital conversion.