Standard Time and frequency :

Abstract

The Time and Frequency Division of the National Bureau of Standards produces the NBS time scales, AT(NBS), SAT(NBS), and UTC(NBS). These time scales are developed by utilizing the properties of the NBS frequency standard, NBS-III. The main byproduct of these time scales is the operational clock systems.These operational clock systems are used, among other things, to calibrate the clocks and secondary standards necessary for the operation of the NBS radio stations, WWV, WWVB, WWVL, and WWVH. These stations transmit SAT (NBS), UTC(NBS), and various tones, alerts, and corrections for time-of-day information.