Secondary Frequency Standard

In telecommunications, a secondary frequency standard is a frequency standard that does not have inherent accuracy, and therefore must be calibrated against a primary frequency standard.

Secondary standards include crystal oscillators and rubidium standards. A crystal oscillator depends for its frequency on its physical dimensions, which vary with fabrication and environmental conditions. A rubidium standard is a secondary standard even though it uses atomic transitions, because it takes the form of a gas cell through which an optical signal is passed. The gas cell has inherent inaccuracies because of gas pressure variations, including those induced by temperature variations. There are also variations in the concentrations of the required buffer gases, which variations cause frequency deviations.

Famous quotes containing the words secondary, frequency and/or standard:

    Words are always getting conventionalized to some secondary meaning. It is one of the works of poetry to take the truants in custody and bring them back to their right senses.
    William Butler Yeats (1865–1939)

    One is apt to be discouraged by the frequency with which Mr. Hardy has persuaded himself that a macabre subject is a poem in itself; that, if there be enough of death and the tomb in one’s theme, it needs no translation into art, the bold statement of it being sufficient.
    Rebecca West (1892–1983)

    As long as male behavior is taken to be the norm, there can be no serious questioning of male traits and behavior. A norm is by definition a standard for judging; it is not itself subject to judgment.
    Myriam Miedzian, U.S. author. Boys Will Be Boys, ch. 1 (1991)