A thin slice of semiconducting material, such as a silicon crystal, upon which microcircuits are constructed by diffusion and deposition of various materials. Note: Millions of individual circuit elements, constituting hundreds of microcircuits, may be constructed on a single wafer. The individual microcircuits are separated by scoring and breaking the wafer into individual chips ("dice").
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Acronym for Wide Area Information Servers. 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.
- Browse Related Terms: client ID, client/server, client/server architecture, fat client, network-launched application, newsreader, proxy server, Push, resolver, thin client (computing), thin-client software, WAIS
A graphic image that serves as a background for a Web page or for a computer operating system's screen.
- Browse Related Terms: background, checkbox, Common Gateway Interface, content, cookie, external viewer, file name extension, form, network browser, online shopping, SIG, wallpaper, Web ring, Webmaster, white space
Acronym for wide area network.
- Browse Related Terms: COMINT, FISINT, man, metropolitan area network (MAN), NID, NOD, TASI, VAN, WAN
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Relative to jitter and swim, long-term random variations of the significant instants of a digital signal from their ideal positions. Note 1: Wander variations are those that occur over a period greater than 1 s (second). Note 2: Jitter, swim, wander, and drift have increasing periods of variation in that order.
- Browse Related Terms: block transfer rate, channel reliability (ChR), coasting mode, flip-flop, maximum time interval error (MTIE), Mean Time To Repair (MTTR), measurement period, net loss variation, outage probability, outage ratio, pulse duty factor, reverse-battery signaling, secondary time standard, steady-state throughput, Traffic, wander
A sequence of operations that is performed to reset a previously running system, after an unintentional shutdown. Synonym warm start. 2. In computer operations, the restarting of equipment, after a sudden shutdown, that allows reuse of previously retained initialized input data, retained programs, and retained output queues. Note 1: A warm restart may be needed after a program failure. Note 2: A warm start or restart cannot occur if initial data, programs, and files are not retained after closedown. Synonyms hot boot, warm boot. [From Weik '89]
- Browse Related Terms: applet, automatic data processing (ADP), Bug, complex, computer program, File Server, microcode, module, patch, Pointer, program architecture, program origin, programmable logic array (PLA), registration program, relative address, reset mode, routine, script, self-relative address, Shell., software package, structured programming, switch, system test time, TSPS complex, video description, Virus, warm restart
A statutory exemption pertaining to the acquisition of telecommunications systems that meet the exclusionary criteria of the Warner Amendment, Public Law 97-86, 1 December 1981, which is also known as the Brooks Bill. Note: Use of FTS2000 by U.S. Government agencies is mandatory when telecommunications are required. However, the Warner Amendment excludes the mandatory use of FTS2000 in instances related to maximum security.
- Browse Related Terms: acceptance, certificate hold, command, control and communications (C3), Federal Telecommunications System 2000 service, network management, network security architecture, password length parameter, restriction certificate, security exchange, shadow, signatory authority, tactical communications, Warner exemption
1. A copyright-protection method of embedding a code into a digital audio or video file to attempt to thwart piracy or unlicenced use. 2. In desktop publishing, an inserted (and usually faint) overlay of an image or text onto pages of a document. Note: The watermark is usually visible on the computer screen in WYSIWIG fashion and on the printed pages of the final document. The watermark often verifies authenticity of authorship or release authority.
- Browse Related Terms: archive file, archiving, AVI (.avi), backward recovery, cinepak, compound document, file, M-PEG, MP3, RIP, SMIL, split screen, tag image file format (TIFF), TIFF, watermark
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At a point in an electromagnetic wave, the ratio of the electric field strength to the magnetic field strength. Note 1: If the electric field strength is expressed in volts per meter and the magnetic field strength is expressed in ampere-turns per meter, the wave impedance will have the units of ohms. The wave impedance, Z, of an electromagnetic wave is given by where is the magnetic permeability and ε is the electric permittivity. For free space, these values are 4 ÃÂ 10-7 H/m (henries per meter) and (1/36) F/m (farads per meter), from which 120, i.e., 377, ohms is obtained. In dielectric materials, the wave impedance is 377/n, where n is the refractive index. Note 2: Although the ratio is called the wave impedance, it is also the impedance of the free space or the material medium.
- Browse Related Terms: characteristic impedance (Zo), field intensity, field strength, Maxwell's equations, mode, primary time standard, root-mean-square (rms) deviation, shield, wave equation, wave impedance
A device used to exclude unwanted frequency components, such as noise or other interference, of a wave. Note: Traps are usually tunable to permit selection of unwanted or interfering signals. [From Weik '89]
- Browse Related Terms: adjacent-channel interference, bandpass limiter, Bandwidth, blanketing, blanketing area, co-channel interference, FM blanketing, multilayer filter, sending-end crossfire, speech-plus-duplex operation, undisturbed day, unintentional interference, wave trap
The surface defined by the locus of points that have the same phase, i.e., have the same path length from the source. [After 2196] Note 1: The wavefront is perpendicular to the ray that represents an electromagnetic wave. Note 2: The plane in which the electric and magnetic field vectors lie is tangential to the wavefront at every point. Note 3: The vector that represents the wavefront indicates the direction of propagation. Note 4: For parallel, i.e., collimated, rays, the wavefront is plane. For rays diverging from a point, or converging toward a point, the wavefront is spherical. For rays with varying divergence or convergence, the wavefront has other shapes, such as ellipsoidal and paraboloidal, depending on the nature of the source.
- Browse Related Terms: axial ratio, circular polarization, Faraday effect, magneto-ionic double refraction, magneto-optic effect, plane wave, polarization, Poynting vector, right-hand (or clockwise) polarized wave, wavefront
A material medium that confines and guides a propagating electromagnetic wave. Note 1: In the microwave regime, a waveguide normally consists of a hollow metallic conductor, usually rectangular, elliptical, or circular in cross section. This type of waveguide may, under certain conditions, contain a solid or gaseous dielectric material. Note 2: In the optical regime, a waveguide used as a long transmission line consists of a solid dielectric filament (optical fiber), usually circular in cross section. In integrated optical circuits an optical waveguide may consist of a thin dielectric film. Note 3: In the rf regime, ionized layers of the stratosphere and refractive surfaces of the troposphere may also act as a waveguide.
- Browse Related Terms: cladding diameter, concentricity error, core diameter, ovality, self-focusing, tolerance field, waveguide
Scattering (other than material scattering) that is attributable to variations of geometry and refractive index profile of an optical fiber.
- Browse Related Terms: fiber axis, near-field region, near-field scanning, optical axis, parabolic profile, profile parameter (g), Refraction, refractive index profile, soliton, step-index fiber, tapered fiber, waveguide scattering, weakly guiding fiber