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NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 cesium fountain atomic clock, a civilian time standard for the United States. NIST-F2 is a caesium fountain atomic clock that, along with NIST-F1, serves as the United States' primary time and frequency standard. [1] NIST-F2 was brought online on 3 April 2014. [1] [2]
NIST-F1, source of the official time of the United States. NIST-F1 is a cesium fountain clock, a type of atomic clock, in the National Institute of Standards and Technology (NIST) in Boulder, Colorado, and serves as the United States' primary time and frequency standard. The clock took fewer than four years to test and build, and was developed ...
This is a list of some experimental laboratory atomic clocks worldwide. ... Colorado United States [11] ... National Standard Time and Frequency Laboratory;
The high frequency of caesium allows for more accurate measurements. Caesium reference tubes suitable for national standards currently last about seven years and cost about US$35,000. Primary frequency and time standards like the United States Time Standard atomic clocks, NIST-F1 and NIST-F2, use far higher power. [34] [70] [71] [72]
Manual sync only. NIST Automated Computer Time Service (ACTS) [27] +1-303-494-4774 +1-808-335-4721; Windows computer with dialup modem. ntpd with NIST/USNO/PTB Modem Time Services driver; ClockWatch Pro for Windows [22] USNO Master Clock modem time [28] +1-202-762-1594 Computer with Bell 212A or CCITT V.22 compatible modem US Naval Observatory ...
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The master atomic clock ensemble at the U.S. Naval Observatory in Washington D.C., which provides the time standard for the U.S. Department of Defense. [1] The rack mounted units in the background are caesium beam clocks. The black units in the foreground are hydrogen maser standards.