An automatic device for tracing the wave form of a repetitive oscilloscope pattern has been developed. The wave form is accurately reproduced and enlarged 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 used with a high‐frequency traveling‐wave oscilloscope the method is applicable to phenomena in the millimicro‐second region and is capable of utilizing time resolution down to 0.1 m&mgr;sec. Deflections as small as one micron may be detected. In addition to making oscilloscope measurements faster and more convenient, certain distortions normally encountered in oscilloscopes are obviated.