An automatic device for tracing the waveform of a repetitive oscilloscope pattern has been developed. The waveform is accurately reproduced and magnified by a conventional X-Y recorder. Because optical and pulse techniques are used the system is capable of reproducing signals displayed on even the fastest available oscilloscopes. When useil with a high-frequency traveling-wave oscilloscope, the method is applicable to phenomena in the millimicrosecond region and is capable of utilizing time resolution down to 0.1 m ic sec. Deflections as small as one micron niay be detected. In addition to making oscilloscope measurements faster and more convenient, many of the sources of distortion normally encountered in oscilloscopes are eliminated. (auth)