The Type 1110-A Interpolating Frequency Standard is designed as a means to improve greatly the accuracy of frequency measurements made with the heterodyne- frequency m eters, such as the Types 720-A and 620-A. The Type 1110-A Interpolating Frequency Standard comprises a standard frequency source having a range of 1 per cent, from 1000 to 1010 kc, and is used with the Type 1110-Pl, a harmonic generator of the multivibrator type which generates multiples of lM c and 100 kc. By adjustment of the frequency of the standard, complete coverage is obtained at frequencies above 100 Me, usiig 1 Me harmonics and above 10 Me, using 100 kc harmonics. Thus integral standard frequencies can be generated for calibration purposes, or an accurately known frequency can be generated to match any desired frequency. With the Type 620-A Heterodyne Frequency Meter, the approximate range of measurement is from 10 Me to 200 Me. With the Type 720-A Heterodyne Frequency Meter, the range is from 100 Me to 2000 Me. The dial setting for zero beat with the unknown signal, either fun­ damental or harmonic, is obtained in the usual manner on the heterodyne frequency m eter. The Type 1110-A Interpolating Frequency Standard provides a means of evaluating more precisely the frequency to which the dial is set.