- 行业: Telecommunications
- Number of terms: 29235
- Number of blossaries: 0
- Company Profile:
ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven standards for the information, entertainment and communications industry.
In analog color television technology, a signal superimposed upon the picture (gray scale) information for the purpose of conveying the associated color information. Note: The color information is conveyed by the instantaneous phase of the color subcarrier with respect to that of the color burst.
Industry:Telecommunications
In analog color television technology, a signal consisting of several (8 to 10 in NTSC) cycles of unmodulated color subcarrier, superimposed at a specified location within the composite signal. Note: The color burst (a) enables the color-decoding circuits in the receiver, and (b) serves as an amplitude, frequency, and phase reference to which the local color (subcarrier frequency) oscillator in the receiver is phase-locked to ensure color fidelity and stability in the displayed picture.
Industry:Telecommunications
In analog (usually audio) systems, reduction of the dynamic range of a signal by controlling it as a function of the inverse relationship of its instantaneous value relative to a specified reference level. Note 1: Signal compression is usually expressed in dB. Note 2: Instantaneous values of the input signal that are low, relative to the reference level, are increased, and those that are high are decreased. Note 3: Signal compression is usually accomplished by separate devices called "compressors. " It is used for many purposes, such as (a) improving signal-to-noise ratios prior to digitizing an analog signal for transmission over a digital carrier system, (b) preventing overload of succeeding elements of a system, or (c) matching the dynamic ranges of two devices. Note 4: Signal compression (in dB) may be a linear or nonlinear function of the signal level across the frequency band of interest and may be essentially instantaneous or have fixed or variable delay times. Note 5: Signal compression always introduces distortion, which is usually not objectionable, if the compression is limited to a few dB. Note 6: The original dynamic range of a compressed signal may be restored by a circuit called an "expander. " 2. In facsimile systems, a process in which the number of pels scanned on the original is larger than the number of encoded bits of picture information transmitted.
Industry:Telecommunications
In an rf antenna, one or more conducting elements or surfaces that reflect incident radiant energy. Note: A reflector may consist of a large surface, as in a dish antenna, or a linear element, as in a Yagi antenna. 2. See mail reflector.
Industry:Telecommunications
In an otherwise essentially flat-topped rectangular pulse, distortion characterized by a decline of the pulse top.
Industry:Telecommunications
In an oscillator, the continuation of oscillations after removal of the control stimulus. Note 1: The flywheel effect is usually caused by interacting inductive and capacitive circuits in the oscillator. Note 2: The flywheel effect may be desirable, such as in phase-locked loops used in synchronous systems, or undesirable, such as in voltage-controlled oscillators. Synonym flywheeling.
Industry:Telecommunications
In an optical waveguide, sharp curvatures involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters. Note: Microbends can result from waveguide coating, cabling, packaging, and installation. Microbending can cause significant radiative loss and mode coupling.
Industry:Telecommunications
In an oscillator, rapid, short-term, random fluctuations in the phase of a wave, caused by time-domain instabilities. Note: Phase noise, in decibels relative to carrier power (dBc) on a 1-Hz bandwidth, is given by = 10log where S (f) is the spectral density of phase fluctuations.
Industry:Telecommunications
In an orbit of a satellite orbiting the Earth, the point that is farthest from the gravitational center of the Earth.
Industry:Telecommunications
In an optical waveguide, sharp curvatures involving local axial displacements of a few micrometers and spatial wavelengths of a few millimeters. Note: Microbends can result from waveguide coating, cabling, packaging, and installation. Microbending can cause significant radiative loss and mode coupling.
Industry:Telecommunications
