ATIS Telecom Glossary
Tuesday, October 21, 2014

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cesium standard
A primary frequency standard in which electronic transitions between the two hyperfine ground states of cesium-133 atoms control the output frequency. Note 1: The difference between the energy levels of the two hyperfine ground states of the cesium-133 atom corresponds, in the absence of external influences (e.g., the magnetic field of the Earth), to electromagnetic radiation having a frequency of precisely 9,192,631,770 Hz (microwave regime). Note 2: The preceding is exact because by internationally recognized (SI) definition, the second is the interval required for 9,192,631,770 cycles of this radiation to occur in the absence of external influences. A very slightly higher, but known and controlled, transition rate occurs in realizeable cesium standards, making the second by far the most precisely determined SI base unit.

 

 

 

 

 

 

 

 

 

 



 
These definitions were prepared by ATIS Committee PRQC
 
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