A stable oscillator used for frequency calibration or reference.
Note 1: A frequency standard generates a fundamental frequency with a high degree of accuracy and precision. Harmonics of this fundamental frequency are used to provide reference points.
Note 2: Frequency standards in a network or facility are sometimes administratively designated as "primary" or "secondary. " The terms "primary" and "secondary,"… (Read More →)

A device that produces frequencies that are phase coherent with a reference frequency.
Note: The reference frequency may be derived from an internal or external source.

1. The maximum permissible departure by the center frequency of the frequency band occupied by an emission from the assigned frequency, or by the characteristic frequency of an emission from the reference frequency. Frequency tolerance is expressed in parts per 106 or in hertz. [NTIA] [RR]
Note: In the United States, frequency tolerance is expressed in parts per 10n, in… (Read More →)

The transfer of signals occupying a specified frequency band, such as a channel or group of channels, from one portion of the frequency spectrum to another, in such a way that the arithmetic frequency difference of signals within the band is unaltered.

Data compaction accomplished by using an expression composed of a number of different frequencies of different magnitudes to represent a particular curve.
Note: An example of frequency-analysis compaction is the use of a Fourier analysis to represent an arbitrary curve, a periodic function, an aperiodic function, or a wave shape. Thus, the fundamental frequency, the amplitude of the fundamental frequency,… (Read More →)

A signaling method in which one or more discrete frequencies correspond to each desired significant condition of a code.
Note 1: The transition from one set of frequencies to the other may be a continuous or a discontinuous change in frequency or in phase.
Note 2: Frequency-change signaling may be used in both supervisory signaling and data transmission.

A channel derived by dividing an allocated or available bandwidth over a medium into two or more portions, each usable separately.
Note: A frequency-derived channel is continuously available and may be further divided on either a frequency or time basis.

The use of frequency division to provide multiple and simultaneous transmissions to a single transponder.

The deriving of two or more simultaneous, continuous channels from a transmission medium by assigning a separate portion of the available frequency spectrum to each of the individual channels.

Frequency-change signaling in which the change from one significant condition to another is accompanied by decay in amplitude of one or more frequencies and by buildup in amplitude of one or more other frequencies.
Note: Frequency-exchange signaling applies to supervisory signaling and user-information transmission. Synonym two-source frequency keying.