This Standard is a revision of Part 1 of Standard 50 IRE 23. S1 and replaces in all respects this previously issued part of the Standard. The need for the revision stems from the standardization of color television signals in the USA, and the inadequacy of the earlier Standard in providing methods of measuring the luminance component of the color signal. The revision consists primarily of a change in the response characteristics of the oscilloscopes to insure adequate suppression of the color subcarrier. Other minor changes in wording and in the associated figures have been made to bring the standard into accord with present terminology and practice.