In 1923, in order to meet the growing needs of the broadcast industry, NIST initiated radio broadcasts of frequency signals that continue to this day, although these now include time information as well. NIST Radio Broadcasts originated from a series of locations initially on the East Coast and later in Colorado. In the process of restating and expanding the mission of NIST in 1950, the Congress recognized the importance of this activity by including the function of "broadcasting of radio signals of standard frequency." Current NIST radio signals now emanate from broadcast stations WWV and WWVB located just north of Fort Collins, Colorado and from WWVH (right) located on the island of Kauai, Hawaii. NIST also offers two services designed to synchronize computer clocks and other automated equipment at modest accuracy levels: the Automated Computer Time Service (ACTS), and the rapidly growing Internet Time Service.
Concurrent with the development of more recent NIST atomic standards has been the development of methods for transferring time and frequency over large distances with the full accuracy of the most accurate standards. Without such transfer capability, these new atomic standards would serve no useful purpose. In the early 1980's, NIST developed the first really successful, high-accuracy technique for transferring time using satellites. This technique, called GPS Common-View Time Transfer, is now the standard method used to coordinate time among the various major timekeeping laboratories of the world. Still more accurate transfer is achieved using the methods of Two-Way Satellite Time Transfer and Carrier-Phase GPS Measurements.
With the growth of the standards and measurement methods over many years, the organizational structure of NIST's program changed. Early work took place within the Weights and Measures Section, the Electricity Division, and then the Radio Laboratory in Washington. In 1954, radio work at NIST was moved to the new Boulder Laboratories in Colorado where the work continued under the heading of the Time and Frequency Section of the Radio Standards Laboratory. In 1967, growth of the program led to the formation of the Time and Frequency Division. The final phase of the move of the WWV and WWVB radio broadcasts from the East Coast to Colorado was achieved in 1966.
An interesting aside in this history is the 1980 award by the television broadcast industry of an Emmy for contributions to the development of Closed Captioning for the Hearing Impaired. NBS work on this topic started out as a method for dissemination of time through TV broadcasts.
For a much more detailed history, please download the following paper:
D. B. Sullivan, Time and Frequency Measurement at NIST: The First 100 Years, Proc. 2001 IEEE Frequency Control Symposium, pp. 4-17, June 2001.