Telecommunications terms starting with H

164 terms

H-bend A smooth change in the direction of the axis of a waveguide, throughout which the axis remains in a plane parallel to the direction of magnetic H-field…
H-channel In Integrated Services Digital Networks (ISDN), a 384-kb/s, 1472-kb/s, or 1536-kb/s channel, designated as "H0", "H10", and "H11", respectively…
H-plane bend Synonym H-bend.
HA1-receiver weighting A noise weighting used in a noise measuring set to measure noise across the HA1-receiver of a 302-type or similar instrument.
hack 1. To break into or use a computer network or use a system without authorization, as a hacker might do. 2.
Hacker Someone who breaks into computer systems in order to steal, change or destroy information.
Hagelbarger code A convolutional code that enables error bursts to be corrected provided that there are relatively long error-free intervals between the error bursts.
half-duplex (HDX) operation Operation in which communication between two terminals occurs in either direction, but in only one direction at a time.
Halftone See Dithering.
halftone characteristic In facsimile systems, the relationship between the density of the recorded copy and the density of the object, i.e., the original. 2.
Hamming code An error-detecting and error-correcting binary code, used in data transmission, that can (a) detect all single- and double-bit errors and (b) correct all…
Hamming Distance The number of non-corresponding digits in a string of binary digits; used to measure dissimilarity.
Hamming weight The number of non-zero symbols in a symbol sequence. Note: For binary signaling, Hamming weight is the number of "1" bits in the binary sequence.
handoff This occurs when information on positions, velocities and tracks are given by one sensor or system to another and the first sensor or system continues to…
Handover This occurs when information is passed on to another sensor or system in which the first does not continue to track.
handshaking In data communications, a sequence of events governed by hardware or software, requiring mutual agreement of the state of the operational modes prior to…
handshaking procedures [The] dialogue between two information systems for synchronizing, identifying, and authenticating themselves to one another. [INFOSEC-99]
hang-up Calling- or called-user placement of a telephone set or other unit of telecommunications equipment in the quiescent state. [T1.104-1988]
hang-up signal An on-hook signal sent from an end office toward the disconnect-control office indicating either calling or called user hang-up and requesting the…
hangover Synonym tailing.
hard copy Synonymous with paper
Hard disk A magnetic disk on which data can be stored.
hard limiting See limiting.
hard sectoring In magnetic or optical disk storage, sectoring that uses a physical mark on the disk, from which mark sector locations are referenced.
hard-copy key [A] physical keying material, such as printed key lists, punched or printed key tapes, or programmable, read-only memories (pROM). [INFOSEC-99]
hard-drawn copper wire Copper wire that has not been annealed after being drawn.
hardened Pertaining to the condition of a facility with protective features that enable it to withstand destructive forces, such as explosions, natural disasters…
hardware The physical components of a computer system-the computer, plotters, printers, terminals, digitizers, and so on.
hardware platform Synonym platform.
hardwire To connect equipment or components permanently in contrast to using switches, plugs, or connectors. 2.
hardwired key [A] permanently installed key. [INFOSEC-99]
harmful interference Any emission, radiation, or induction interference that endangers the functioning or seriously degrades, obstructs, or repeatedly interrupts a…
harmonic Of a sinusoidal wave, an integral multiple of the frequency of the wave. Note: The frequency of the sine wave is called the fundamental frequency or the…
harmonic distortion In the output signal of a device, distortion caused by the presence of frequencies that are not present in the input signal.
Harmonization The proposed harmonizing of patent laws in different countries to produce essentially one, worldwide patent law.
Hash Function A function used to create a hash value from binary input. The hash is substantially smaller than the text itself, and is generated by the hash function in…
hash total The result obtained by subjecting a set of data to an algorithm for purposes of checking the data at the time the algorithm is applied or for use at a…
hash value In cryptography, the result of applying a cryptologic hash function to a message. [After X9.31]
Hashing The process of using a mathematical algorithm against data to produce a numeric value that is representative of that data.
hashword [The] memory address containing [a] hash total. [INFOSEC-99]
hazards of electromagnetic radiation to fuel (HERF) The potential for electromagnetic radiation to cause ignition or detonation of volatile combustibles, such as aircraft fuels.
hazards of electromagnetic radiation to ordnance (HERO) The potential for electromagnetic radiation to affect adversely munitions or electroexplosive devices.
hazards of electromagnetic radiation to personnel (HERP) The potential for electromagnetic radiation to produce harmful biological effects in humans.
HDLC Abbreviation for high-level data link control.
HDTV Abbreviation for high-definition television.
HDX Half Duplex ( TelComm /Computer term).
HE11 mode Designation for the fundamental hybrid mode of an optical fiber.
Head The upper horizontal part of a window frame or window opening.
head end See cable headend, headend.
head-of-bus function The function that generates management information and empty bus slots at the point on each bus where data flow begins.
head-on collision A collision that occurs on a communications channel when two or more users begin to transmit on the channel at approximately the same instant.
headend A central control device required by some networks (e.g., LANs or MANs) to provide such centralized functions as remodulation, retiming, message…
Header A masonry wall unit of brick which is laid so that its short end is exposed.
header check sequence (HCS) A 16-bit cyclic redundancy check (CRC) check sequence (CS) that is derived from bits from the first 8 octets (excluding flags) of a UIH format packet. [T1.
Heaviside layer Synonym E region.
height gain For a given propagation mode of an electromagnetic wave, the ratio of the field strength at a specified height to the field strength at the surface of the…
helical antenna An antenna that has the form of a helix. Note: When the helix circumference is much smaller than one wavelength, the antenna radiates at right angles to…
helical scan A method of recording video information diagonally on a tape, used in home and professional video cassette recorders (VCRs).
HEMP High Altitude Electromagnetic Pulse. 126
HERF Abbreviation for hazards of electromagnetic radiation to fuel.
HERO Hazards of Electromagnetic Radiation to Ordnance (SM-2 Bk IVA).
HERP Abbreviation for hazards of electromagnetic radiation to personnel.
Hertz (Hz) The unit of measurement of frequency, equivalent to one cycle per second.
Hertzian wave Synonym radio wave.
heterochronous A relationship between two signals such that their corresponding significant instants do not necessarily occur at the same time.
heterodyne To generate new frequencies by mixing two or more signals in a nonlinear device such as a vacuum tube, transistor, or diode mixer.
heterodyne repeater In radio reception and retransmission, a repeater that converts the original band of frequencies of the received signal to a different frequency band for…
heterogeneous multiplexing Multiplexing in which not all the information-bearer channels operate at the same data signaling rate.
heuristic routing Routing in which data, such as time delay, extracted from incoming messages, during specified periods and over different routes, are used to determine the…
hexadecimal A number system with a base of 16. The digits are 0-9 and A-F, where F equals the decimal value of 15.
HF (1) High Frequency. (2) Hydrogen fluoride.
HFDF Abbreviation for high-frequency distribution frame.
hierarchical computer network A computer network in which processing and control functions are performed at several levels by computers specially suited for the functions performed…
hierarchical routing Routing that is based on hierarchical addressing. Note: Most Transmission Control Protocol/Internet Protocol (TCP/IP) routing is based on a two-level…
hierarchically synchronized network A mutually synchronized network in which some clocks exert more control than others, the network operating frequency being a weighted mean of the natural…
High Definition Television (HDTV) Television that has approximately twice the horizontal and twice the vertical emitted resolution specified by the NTSC standard.
High Frequency (HF) The portion of the radio frequency spectrum between between 3 and 30 MHz
high probability of completion (HPC) With reference to American National Standard ANSI T1.631-1993, an aspect of National Security and Emergency Preparedness (NS/EP) telephone calls, as…
High Sierra format A standard format for placing fields and directories on CD ROM, revised and adopted by the International Organization for Standardization as ISO 9660.
high-altitude electromagnetic pulse (HEMP) An electromagnetic pulse produced at an altitude effectively above the sensible atmosphere, i.e., above about 120 km.
high-frequency distribution frame (HFDF) A distribution frame that provides terminating and interconnecting facilities for those combined supergroup modulator output circuits and combined…
high-level control In the hierarchical structure of a primary or secondary data transmission station, the conceptual level of control or processing logic that (a) is above…
high-level data link control (HDLC) A Link-Level protocol used to facilitate reliable point-to-point transmission of a data packet.
high-level language (HLL) A computer programming language that is primarily designed for, and syntactically oriented to, particular classes of problems and that is essentially…
high-order language Synonym high-level language.
high-pass filter A filter that passes frequencies above a given frequency and attenuates all others.
high-performance equipment Equipment that (a) has the performance characteristics required for use in trunks or links, (b) is designed primarily for use in global and tactical…
high-priority emergency service call A call identified as receiving emergency service treatment, which has been marked as requiring special treatment by the emergency service administration.
high-usage trunk group A group of trunks for which an alternate route has been provided to absorb the relatively high rate of overflow traffic.
higher frequency ground Deprecated term name. See facility grounding system.
highway A digital serial-coded bit stream with time slots allotted to each call on a sequential basis. 2.
hiss Noise in the audio frequency range, having subjective characteristics analogous to prolonged sibilant sounds.
history list A record of the documents visited during a Web session, which list allows users to access previously visited pages more quickly or to generate a record of…
Hit To take another card.
hit counter An indicator on a Web page that graphically displays the number of previous users that have accessed the page.
HLL Abbreviation for high-level language.
hockey puck A polishing fixture used to facilitate the manual finishing of the endfaces of certain types of optical fiber connectors.
hold-in frequency range The range of frequencies over which a phase-locked loop can vary and still maintain frequency lock.
hold-in range See hold-in frequency range.
holding time The total length of time that a call makes use of a trunk or channel. Note: Holding time is usually measured in seconds. 2.