Frequency standard

Harmonics of this fundamental frequency are used to provide reference points.

Frequency standards in a network or facility are sometimes administratively designated as primary or secondary.

The terms primary and secondary, as used in this context, should not be confused with the respective technical meanings of these words in the discipline of precise time and frequency.

Caesium standards are widely recognized as having better long-term stability, whereas hydrogen masers can attain superior short-term performance; therefore, several national standards laboratories use ensembles of caesium standards and hydrogen masers in order to combine the best attributes of both.

The carrier of time signal transmitters, Loran-C transmitters and of several long wave and medium wave broadcasting stations is derived from an atomic clock and can be therefore used as frequency standard.