The Navy's Primary Frequency Standard
R.H. Worrall, R. B. Owens · Proceedings of the IRE · 1928
In this paper is described a constant frequency source which is used as the Navy's primary working standard of frequency. This frequency source is a crystal-controlled oscillator of special design which was developed at the U.S. Naval Research Laboratory, Washington, D.C. This oscillator employs a type of circuit which is rich in harmonics, over 200 of which may be used as fixed standard frequencies. It also describes in detail the method employed to determine the fundamental frequency of this standard in terms of Naval Observatory time to an accuracy of about one part in 100,000. The ultimate standard of frequency is therefore the mean solar day.