Some months ago the RCA License Laboratory, in connection with television development, had occasion to make measurements on the spectral characteristics of optical filters. The conventional and elaborate equipment usually used for such purposes was not immediately at hand, and a cathode‐ray oscilloscope coupled to a few simple appurtenances was pressed into service and gave highly satisfactory results. The equipment is easily duplicated and possesses sufficient accuracy for many uses. Design considerations and constructional details are given.