Telecommunications — page 24 of 85

Telecommunications terms

2301. Dirac delta function Synonym unit impulse.
2302. direct access The ability of an electric power consumer to purchase electricity from a supplier of their choice without being physically inhibited by the owner of the…
2303. direct address In computing, an address that designates the storage location of an item of data to be treated as an operand.
2304. direct bond An electrical connection using continuous metal-to-metal contact between the members being joined.
2305. Direct Broadcast Satellite (DBS/DISH) A high-powered satellite that transmits or retransmits signals which are intended for direct reception by the public.
2306. direct broadcast satellite radio See satellite digital audio radio service.
2307. direct call A facility-handled call in which the network interprets the call request signal as an instruction to establish a connection based on previously designated…
2308. direct connect 1. In computer systems, a permanent communications link that connects directly to a mainframe computer through a terminal controller, usually at binary…
2309. direct coupling Synonym conductive coupling.
2310. direct current signaling (DX signaling) In telephony, a method whereby the signaling circuit E & M leads use the same cable pair(s) as the voice circuit and no filter is required to separate the…
2311. direct detection See detection.
2312. direct dialing service A service feature that permits a user to place information concerning credit card calls, collect calls, and special billing calls into the public…
2313. direct distance dialing (DDD) A network-provided service feature in which a call originator may, without operator assistance, call any other user outside the local calling area.
2314. direct inward dialing (DID) A service feature that allows inward-directed calls to a PBX to reach a specific PBX extension without human intervention. Synonym network inward dialing.
2315. direct orbit For a satellite orbiting the Earth, an orbit in which the projection of the satellite on the equatorial plane revolves about the Earth in the same…
2316. direct outward dialing (DOD) An automated PBX service feature that provides for outgoing calls to be dialed directly from the user terminal. Synonym network outward dialing.
2317. direct ray A ray of electromagnetic radiation that follows the path of least possible propagation time between transmitting and receiving antennas.
2318. direct recording In facsimile systems, recording in which a visible record is produced, without subsequent processing, in response to received signals.
2319. direct-buried cable A communication cable manufactured or produced for the purpose of burial in direct contact with the earth.
2320. direct-sequence modulation In spread-spectrum systems, modulation in which a sequence of binary pulses is used directly to modulate a carrier, usually by phase-shift keying.
2321. direct-sequence spread spectrum 1. A system (a) for generating spread-spectrum transmissions by phase-modulating a sine wave pseudorandomly with a continuous string of pseudonoise code…
2322. direct-spread modulation Synonym direct-sequence modulation.
2323. directed broadcast address An Internet Protocol address that specifies "all hosts" on a specified network.
2324. directed net A radio net in which no station other than the net control station may communicate with any other station without first obtaining permission from the net…
2325. direction finding A procedure for obtaining bearings of radio frequency emitters by using a highly directional antenna and a display unit on an intercept receiver or…
2326. direction of scanning In a facsimile transmitting apparatus, the scanning of the plane (developed in the case of a drum transmitter) of the message surface along lines running…
2327. directional antenna An antenna in which the radiation pattern is not omnidirectional, i.e., a nonisotropic antenna.
2328. directional coupler A transmission coupling device for separately sampling (through a known coupling loss) either the forward (incident) or the backward (reflected) wave in a…
2329. directionalization The temporary conversion of a portion or all of a two-way trunk group to one-way trunks favoring traffic flowing away from a congested switch.
2330. directive gain Of an antenna, the ratio of (a) 4 times the radiance, i.e., power radiated per unit solid angle (watts per steradian), in a given direction to (b) the…
2331. directivity pattern Synonym radiation pattern.
2332. directory access protocol (DAP) A directory protocol that defines the exchange of requests and outcomes between user and system. [T1.667-1999]
2333. Directory Assistance (DA) A service providing the requested telephone number for a given name and address.
2334. Directory Assistance Call Completion (DACC) After the telephone number has been received, DACC is a service that permits a call to be completed to the requested number, typically at the calling…
2335. directory number A network (sub)address (from a telephone user perspective) such as the telephone number in the telecommunication network.
2336. directory server (DS) A unit consisting of a DSA (directory system agent) and possibly other application processes (such as registration management) to provide the directory…
2337. directory system agent (DSA) The software that provides the X.500 directory service for a portion of the directory information base.
2338. directory user agent (DUA) The software that accesses the X.500 directory service on behalf of the directory user.
2339. Disabled When applied to privilege: a privilege that is inactive, i.e., has its effective flag cleared [POSIX.6].
2340. disabling tone A tone, transmitted over a communications path, used to control equipment. Note: An example of a disabling tone is a tone that places an echo suppressor…
2341. disaster recovery plan A written and approved course of action to take after a disaster strikes that details how an organization will restore critical business functions and…
2342. disc See diskette.
2343. disciplined development Development of a system or part of a system where the documentation and evidence of testing against the documentation is to normal industry standards.
2344. disclosure A disclosure document explains how a financial product or offering works. It also details the terms to which you must agree in order to buy it or use it…
2345. discone antenna See biconical antenna.
2346. disconnect In telephony, the disassociation or release of a switched circuit between two stations.
2347. disconnect command (DISC) In Link-Layer protocols, such as high-level data link control (HDLC), synchronous data link control (SDLC), and advanced data communication control…
2348. disconnect signal In a switched telephone network, a supervisory signal transmitted from one end of a user line or trunk to indicate at the other end that the established…
2349. disconnect switch In a power system, a switch used for closing, opening, or changing the connections in a circuit or system or for purposes of isolation.
2350. disconnect timing The timing of the period during which a hang-up signal is being received from the called end office and an off-hook signal is being received from the…
2351. disconnect-control office The switching entity that performs disconnect timing and that decides when the connection is to be cleared.
2352. discretionary access control (DAC) 1. [A] means of restricting access to objects based on the identity and need-to-know of users and/or groups to which the object belongs.
2353. discriminator The part of an FM receiver that extracts the desired signal from an incoming FM wave by changing frequency variations into amplitude variations.
2354. discussion group Synonym forum.
2355. discussion list Synonym forum.
2356. discussion thread In a discussion board or Web discussions, a series of messages or comments in which replies to a message or comment are nested directly under it, instead…
2357. disengagement attempt An attempt to terminate a telecommunications system access. Note: Disengagement attempts may be initiated by a user or the telecommunications system.
2358. disengagement denial After a disengagement attempt, a failure to terminate the telecommunications system access.
2359. disengagement failure Failure of a disengagement attempt to return a communication system to the idle state, for a given user, within a specified maximum disengagement time.
2360. disengagement originator The user or functional unit that initiates a disengagement attempt. Note 1: A disengagement originator may be the originating user, the destination user…
2361. disengagement phase In an information transfer transaction, the phase during which successful disengagement occurs.
2362. disengagement request A control or overhead signal issued by a disengagement originator for the purpose of initiating a disengagement attempt.
2363. disengagement time The average value of elapsed time between the start of a disengagement attempt for a particular source or destination user and the successful…
2364. disengagement-denial probability The ratio of disengagement attempts that result in disengagement denial to the total disengagement attempts counted during a measurement period.
2365. disk and execution monitor (daemon) See daemon.
2366. disk pack An assembly of magnetic disks that can be removed as a whole from a disk drive together with a container from which the assembly must be separated when…
2367. diskette An inexpensive, low-capacity storage medium, usually measuring 3.5 inches in diameter, often referred to as a floppy disk.
2368. disparity In pulse-code modulation (PCM), the digital sum, i.e., the algebraic sum, of a set of signal elements.
2369. Dispersion Distortion of the shape of a seismic-wave train because of variation of velocity with frequency.
2370. dispersion coefficient See material dispersion coefficient.
2371. dispersion-limited operation Operation of a communications link in which signal waveform degradation attributable to the dispersive effects of the communications medium is the…
2372. dispersion-shifted fiber A single-mode optical fiber that has its minimum-dispersion wavelength shifted, by the addition of dopants, toward its minimum-loss wavelength.
2373. dispersion-unmodified fiber Synonym dispersion-unshifted fiber.
2374. dispersion-unshifted fiber A single-mode optical fiber that has a nominal zero-dispersion wavelength in the 1.3-m transmission window.
2375. display device An output unit that gives a visual representation of data.
2376. dissolve To enter into a solution.
2377. Distance Learning Synonym teletraining.
2378. distance measuring equipment (DME) In radio location systems, equipment that ascertains the distance between an interrogator and a transponder. [From Weik '89]
2379. distance training Synonym teletraining.
2380. distinctive alerting Special ringing or call-waiting tone patterns sent by the network to convey information to a customer installation (CI) about the called number, the…
2381. distinguished name A name that uniquely identifies an object by using the relative distinguished name for the object, plus the names of container objects and domains that…
2382. Distinguishing Identifier Information which unambiguously distinguishes an entity in the authentication process.
2383. distortion In a system or device, any departure of the output signal waveform from that which should result from the input signal waveform's being operated on by the…
2384. distortion-limited operation The condition prevailing when distortion of a received signal, rather than its attenuated amplitude (or power), limits performance under stated…
2385. distributed application An application made up of distinct components running in separate runtime environments, usually on different platforms connected via a network.
2386. distributed computing environment See DCE.
2387. distributed control Control of a network from multiple points. Note: Each point controls a portion of the network, using local information or information transmitted over the…
2388. distributed database 1. A database that is not entirely stored at a single physical location, but rather is dispersed over a network of interconnected computers. 2.
2389. distributed frame-alignment signal A frame-alignment signal in which the signal elements occupy digit positions that are not consecutive.
2390. distributed network A network structure in which the network resources, such as switching equipment and processors, are distributed throughout the geographical area being…
2391. distributed processing Data processing in which an integrated set of functions is performed within multiple, physically separated devices.
2392. distributed switching Switching in which many processor-controlled switching units are distributed, usually close to concentrations of users, and operated in conjunction with a…
2393. distributed-queue dual-bus (DQDB) [network] A distributed multi-access network that (a) supports integrated communications using a dual bus and distributed queuing, (b) provides access to local or…
2394. Distribution The sale of securities. Also refers to a sum payable to shareholders representing their share of profits.
2395. distribution amplifier An active linear device that accepts, at its input port, one signal source (e.g.
2396. distribution frame In communications, a structure with terminations for connecting the permanent wiring of a facility in such a manner that interconnection by…
2397. distribution list server Synonym list server.
2398. distribution service In ISDN applications, a telecommunications service that allows one-way flow of information from one point in the network to other points in the network…
2399. distribution voltage drop The voltage drop between any two defined points of interest in a power distribution system.
2400. distribution-quality television Television conforming to the NTSC standard, the SECAM standard, the PAL standard, or the PAL-M standard.