Described is an instrument for observing or photographing fast voltage transients. It consists of a sweep generator with sweep speeds ranging from 30 cm per microsecond to 0.05 cm per microsecond, a vertical deflection amplifier having a rise time of 0.005 microseconds and a preamplifier which, when used with the deflection amplifier, produces an over‐all rise time of 0.0063 microseconds with a gain of about 1,000. These units are used in conjunction with a type 5XP cathode‐ray tube using 20 kilovolts accelerating voltage.