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- KennyBLv 78 years agoFavorite Answer
NIST-F1 is a cesium fountain clock or 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.
- DickLv 68 years ago
Boulder, Colorado
There web page is http://www.nist.gov/pml/div688/
You might also want to look at the US Naval Observatory page
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