- 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.
A distinctive type of multipoint connection, composed of a central connection endpoint (central CE) and other, peripheral, CEs, and in which data originating from the central CE are received by all other CEs, and data originating from peripheral CEs are received only by the central CE.
Industry:Telecommunications
A distortion mechanism, occurring in multimode fibers, in which the signal is spread in time because the velocity of propagation of the optical signal is not the same for all modes. Note 1: In the ray-optics analogy, multimode distortion in a step-index optical fiber may be compared to multipath propagation of a radio signal. The direct signal is distorted by the arrival of the reflected signal a short time later. In a step-index optical fiber, rays taking more direct paths through the fiber core, i.e., those which undergo the fewest reflections at the core-cladding boundary, will traverse the length of the fiber sooner than those rays which undergo more reflections. This results in distortion of the signal. Note 2: Multimode distortion limits the bandwidth of multimode fibers. For example, a typical step-index fiber with a 50-m core would be limited to approximately 20 MHz for a one-kilometer length, i.e., a bandwidth of 20 MHz•km. Note 3: Multimode distortion may be considerably reduced, but never completely eliminated, by the use of a core having a graded refractive index. The bandwidth of a typical off-the-shelf graded-index multimode fiber, having a 50-m core, may approach 1 GHz•km or more. Multimode graded-index fibers having bandwidths approaching 3 GHz•km have been produced. Note 4: Because of its similarity to dispersion in its effect on the optical signal, multimode distortion is sometimes incorrectly referred to as "intermodal dispersion," "modal dispersion,"or "multimode dispersion. " Such usage is incorrect because multimode distortion is not a truly dispersive effect. Dispersion is a wavelength-dependant phenomenon, whereas multimode distortion may occur at a single wavelength. Synonyms intermodal delay distortion, intermodal distortion, modal distortion.
Industry:Telecommunications
A distortion mechanism, occurring in multimode fibers, in which the signal is spread in time because the velocity of propagation of the optical signal is not the same for all modes. Note 1: In the ray-optics analogy, multimode distortion in a step-index optical fiber may be compared to multipath propagation of a radio signal. The direct signal is distorted by the arrival of the reflected signal a short time later. In a step-index optical fiber, rays taking more direct paths through the fiber core, i.e., those which undergo the fewest reflections at the core-cladding boundary, will traverse the length of the fiber sooner than those rays which undergo more reflections. This results in distortion of the signal. Note 2: Multimode distortion limits the bandwidth of multimode fibers. For example, a typical step-index fiber with a 50-m core would be limited to approximately 20 MHz for a one-kilometer length, i.e., a bandwidth of 20 MHz•km. Note 3: Multimode distortion may be considerably reduced, but never completely eliminated, by the use of a core having a graded refractive index. The bandwidth of a typical off-the-shelf graded-index multimode fiber, having a 50-m core, may approach 1 GHz•km or more. Multimode graded-index fibers having bandwidths approaching 3 GHz•km have been produced. Note 4: Because of its similarity to dispersion in its effect on the optical signal, multimode distortion is sometimes incorrectly referred to as "intermodal dispersion," "modal dispersion,"or "multimode dispersion. " Such usage is incorrect because multimode distortion is not a truly dispersive effect. Dispersion is a wavelength-dependant phenomenon, whereas multimode distortion may occur at a single wavelength. Synonyms intermodal delay distortion, intermodal distortion, modal distortion.
Industry:Telecommunications
A distributed multi-access network that (a) supports integrated communications using a dual bus and distributed queuing, (b) provides access to local or metropolitan area networks, and (c) supports connectionless data transfer, connection-oriented data transfer, and isochronous communications, such as voice communications.
Industry:Telecommunications
A distributed text searching system that uses the protocol standard ANS Z39. 50 to search index databases on remote computers. Note 1: WAIS libraries are most often found on the Internet. Note 2: WAIS allows users to discover and access information resources on the network without regard to their physical location. Note 3: WAIS software uses the client-server model.
Industry:Telecommunications
A distributed-queue dual-bus (DQDB) scheme in which the head-of-bus functions for both buses are at the same location.
Industry:Telecommunications
A distribution frame on one part of which the external trunk cables entering a facility terminate, and on another part of which the internal user subscriber lines and trunk cabling to any intermediate distribution frames terminate. Note 1: The MDF is used to cross-connect any outside line with any desired terminal of the multiple cabling or any other outside line. Note 2: The MDF usually holds central office protective devices and functions as a test point between a line and the office. Note 3: The MDF in a private exchange performs functions similar to those performed by the MDF in a central office. Synonym (in telephony) main frame.
Industry:Telecommunications
A distribution frame that combines the functions of main and intermediate distribution frames and contains both vertical and horizontal terminating blocks. Note 1: The vertical blocks are used to terminate the permanent outside lines entering the station. Horizontal blocks are used to terminate inside plant equipment. This arrangement permits the association of any outside line with any desired terminal equipment. These connections are made either with twisted pair wire, normally referred to as jumper wire, or with optical fiber cables, normally referred to as jumper cables. Note 2: In technical control facilities, the vertical side may be used to terminate equipment as well as outside lines. The horizontal side is then used for jackfields and battery terminations.
Industry:Telecommunications
A distribution frame that provides terminating and interconnecting facilities for those combined supergroup modulator output circuits and combined supergroup demodulator input circuits that contain signals occupying the baseband spectrum.
Industry:Telecommunications
A diversity combiner in which (a) the signals from each channel are added together, (b) the gain of each channel is made proportional to the rms signal level and inversely proportional to the mean square noise level in that channel, and (c) the same proportionality constant is used for all channels. Synonyms ratio-squared combiner, post-detection combiner, predetection combining, selective combiner.
Industry:Telecommunications
