Abbreviation for antenna gain-to-noise-temperature.

Generic Authentication Architecture

The ratio of output current, voltage, or power to input current, voltage, or power, respectively.
Note 1: Gain is usually expressed in dB.
Note 2: If the ratio is less than unity, the gain, expressed in dB, will be negative, in which case there is a loss between input and output.

See hit.

An active medium, device, or system in which amplification of input occurs with or without feedback.
Note: Gain media include amplifiers, lasers, and avalanche photodiodes (APDs).

Synonym antenna gain.

Synonym cosmic noise.

In video, the insertion of a nonlinear output-input characteristic for the purpose of changing the system transfer characteristic. [IEEE 100]
Note: Historically, gamma correction was a precompensation applied to the video signal at the camera to correct for the nonlinearities of the CRT (i.e., the power function of the electron gun) and, as such, it was the inverse of the… (Read More →)

A period of low energy content signals present of a digital speech interpolation device. [T1.509-1995]

1. The power loss that occurs when an optical signal is transferred from one fiber to another that is axially aligned with it, but longitudinally separated from it.
Note: The gap allows light from the "transmitting" fiber to spread out as it leaves the fiber endface. When it strikes the "receiving" fiber, some of the light will enter the cladding,… (Read More →)

An optical attenuator that exploits the principle of gap loss to reduce the optical power level when inserted in-line in the fiber path; e.g., to prevent saturation of the receiver.
Note: Gap-loss attenuators should be used in-line near the optical transmitter. [After FAA]

Periods of no speech activity or low-energy content signals present in the access channel of a wideband packet network. [T1.312-1991]

1. An error in transmission, reception, encryption, or decryption that changes the text of a message or any portion thereof in such a manner that it is incorrect or undecryptable. [JP 1-02]
2. In a telephone circuit or channel, readily audible but unintelligible interference from another circuit or channel.
Note: Garble may, for example, take place in an FDM telephone… (Read More →)

1. A device having one output channel and one or more input channels, such that the output channel state is completely determined by the input channel states, except during switching transients.
2. One of many types of combinational logic elements having at least two inputs; e.g., AND, OR, NAND, and NOR.

1. In a communications network, a network node equipped for interfacing with another network that uses different protocols.
Note 1: A gateway may contain devices such as protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability. It also requires that mutually acceptable administrative procedures be established between the two networks.
Note… (Read More →)

1. The process of selecting only those portions of a wave between specified time intervals or between specified amplitude limits.
2. The controlling of signals by means of combinational logic elements.
3. A process in which a predetermined set of conditions, when established, permits a second process to occur.

A beam of light whose electric field intensity distribution is gaussian.
Note: When such a beam is circular in cross section the intensity at distance r from the center,E(r), is given by where E(0) is the electrical field strength at the beam center, i.e., at r = 0; and w is the value of r at which the intensity is… (Read More →)

A filter having a response curve (magnitude versus frequency) that approximates an ideal gaussian curve.

A pulse that has a waveform described by the gaussian distribution.
Note: In the time domain, the amplitude of the waveform is given by where A is the maximum amplitude, and is the pulse half-duration at the 1/e points.

Giga bit

Gigabyte

Abbreviation for gigabytes per second. See International System of Units.

Generic Bootstrapping Architecture

Gigabit Ethernet

Abbreviation for group busy hour.

Gigabit per second

Gigabyte per second

Abbreviation for Greenwich Civil Time. See Coordinated Universal Time.

Abbreviation for group distribution frame.

1. A substance, resembling petroleum jelly in viscosity, that surrounds a fiber, or multiple fibers, enclosed in a loose buffer tube.
Note: This gel serves to lubricate and support the fibers in the buffer tube. It also prevents water intrusion in the event the buffer tube is breached. [FAA]
2. Index-matching material in the form of a gel. [FAA] Synonyms… (Read More →)

GPON Encapsulation Mode

A computer designed to perform, or that is capable of performing, in a reasonably efficient manner, the functions required by both scientific and business applications.
Note: A general purpose computer is often understood to be a large system, capable of supporting remote terminal operations, but it may also be a smaller computer, e.g., a desktop workstation.

See common user network.

A computer system that is designed to aid in solving a wide variety of problems [TCSEC].

In audio and video analog recording, pertaining to the number of duplication steps between an original recording and a given copy.
Note 1: A second generation duplicate is a copy of the original master and a third generation duplicate is a copy of a copy of the original master, etc.
Note 2: Relative to digital duplication, the copy is almost… (Read More →)

In analog recording, cumulative deterioration of signal quality introduced as a consequence of limitations of the recording electronics and storage medium, when successive copies of an original recording are made, each from the preceding copy.
Note 1: Examples of signal deterioration attributable to generation loss are increased distortion, increased noise, change in frequency response, and change in the relative phase… (Read More →)

The synchronization of two television signals at the vertical, horizontal, and chroma phase levels such that the signals may be cut, mixed, or cross-faded without noticeable roll, jump, or chroma shift.
Note: Modern usage accomplishes this with a frame synchronizer/time base corrector, but it may also be accomplished by a closed loop method or an open loop method, the latter… (Read More →)

The branch of optics that describes light propagation in terms of rays.
Note 1: Rays are bent at the interface between two dissimilar media, and may be curved in a medium in which the refractive index is a function of position.
Note 2: The ray in geometric optics is perpendicular to the wavefront in physical optics. Synonym ray optics.

See inverse-square law.

A circular orbit in the equatorial plane, any point on which revolves about the Earth in the same direction and with the same period as the Earth's rotation.
Note: An object in a geostationary orbit will remain directly above a fixed point on the equator at a distance of approximately 42,164 km from the center of the Earth, i.e., approximately… (Read More →)

A geosynchronous satellite whose circular and direct orbit lies in the plane of the Earth's equator and which thus remains fixed relative to the Earth; by extension, a satellite that remains approximately fixed relative to the Earth. [NTIA] [RR] [47CFR]

The orbit in which a satellite must be placed to be a geostationary satellite. [NTIA] [RR]

Any orbit about the Earth, which orbit has a period equal to the period of rotation of the Earth about its axis, and in the same sense, i.e., direction, as the rotation of the Earth.

A germanium-based PN- or PIN-junction photodiode.
Note 1: Germanium photodiodes are useful for direct detection of optical wavelengths from approximately 1 m to several tens of m.
Note 2: Germanium-based detectors are noisier than silicon-based detectors. Silicon-based detectors are therefore usually preferred for wavelengths shorter than 1 m. [After FAA]

Abbreviation for Government Emergency Telecommunications Service (GETS).

1. Global Functioning Plane,
2. Generic Framing Procedure.

Gateway General Packet Radio Service Support Node

In the transmission or recording of raster-scanned analog television signals, an artifact manifested as a weak, ghost-like secondary image, offset (in the direction of the scan) with respect to the position of the primary image.
Note: Ghosting is probably most familiar as a consequence of multipath rf reception of a broadcast television signal. The slight delay in the arrival time… (Read More →)

See ghost.

(or . gif) Abbreviation for graphical interchange format. A file-name extension indicating a certain digital image file format suitable for efficiently importing image data into computer files or for transmitting or displaying the formatted image on a computer monitor or printing it out.

Global Informaion Grid

A billion, i.e., 109, floating point operations per second.

A unit of frequency denoting 109 Hz.

Abbreviation for global information infrastructure. The totality of worldwide infrastructure elements that combine the three industry sectors of (a) telecommunications, (b) computer (information) technology, and (c) consumer electronics to extend the capabilities of the NII (national information infrastructure) worldwide. [After ISO/IEC N1957]

Deprecated synonym for call collision. See also dual seizure.

The Signaling System No.7 (SS7) switch designated as control switch for circuits in the both-way circuit group. For the same circuits, the other switch is referred to as the slave. On detecting glare, the control switch proceeds to complete the call for which it has already sent an initial address message (IAM). The IAM received from the slave is discarded.… (Read More →)

1. In the strict sense, a state of matter. [FAA]
2. In fiber-optic communication, any of a number of noncrystalline, amorphous inorganic substances, formed, by heating, from metallic or semiconductor oxides or halides, and used as the material for fibers.
Note: The most common glasses are based on silicon dioxide (SiO2). [After FAA]

In aeronautical navigation, an instrument approach landing facility that furnishes vertical guidance information to an aircraft from its approach altitude down to the surface of the runway.

1. Pertaining to, or involving, the entire world.
2. Pertaining to that which is defined in one subsection of an entity and used in at least one other subsection of the same entity.
3. In computer, data processing, and communications systems, pertaining to what is applicable to an area beyond the immediate area of consideration.
Note: Examples of global entities… (Read More →)

In a communications network, the predefined address that is used as an address for all users of that network, and that may not be the address of an individual user, or subgroup of users, of the network.

A network that (a) is composed of different interconnected computer networks and (b) covers an unlimited geographical area.
Note: Loosely synonymous with an internet (as opposed to the Internet (with an uppercase "I"), which designates one specific network). [After 2382-pt.35]

The plane in the intelligent network conceptual model that defines service independent building blocks (SIBs) used in providing service features. [T1.667-1999]

See GII.

A satellite-based global navigation system that consists of (a) a constellation of satellites in orbit 11,000 nmi above the Earth, (b) several on-station (i.e., in-orbit) spares, and (c) a ground-based control segment. The satellites transmit signals that are used for extremely accurate three-dimensional (latitude, longitude, and elevation) global navigation (position determination), and for the dissemination of precise time. GPS-derived position… (Read More →)

A security domain in a System Security policy. The GSE is the general security environment in which the system is located. It covers everything outside the control of the System or Project Manager which may have a bearing on the security of the system and which is therefore deemed to be the responsibility of the DSO [CESG]. See also: Electronic… (Read More →)

1. The set of attributes of an entity, described at a particular time, when that set is extended to every occurrence of that entity within a prescribed boundary.
2. The complete set of attributes necessary to describe an entity at a particular time.

A public, all-digital cellular network that is standardized worldwide and that uses (a) TDMA techniques for multiplexing at approximately 900 MHz, (b) compressed voice at about 13 kb/s, (c) 16 kb/s circuit-switching technology, and (d) error-correcting algorithms.

A "logical" or "virtual" address used for routing Signaling System No.7 (SS7) messages using signaling connection control part (SCCP) capabilities. To complete message routing, a GT must be translated to a SS7 point code and subsystem number. [T1.711-1999]

Any graphic symbol not in the ASCII character set. [After IS 14651]

Gateway Mobile Switching Center

Abbreviation for Greenwich Mean Time. Obsolete term. See Coordinated Universal Time.

Global Navigation Satellite System

Synonyms bookmark list, history list, hotlist.

Synonym go-ahead notice.

In a tape-relay communications system, a service message, usually sent to a relay station or to a tributary station, that contains a request to the operator to resume transmitting over a specified channel or channels. [From Weik '89] Synonyms go-ahead message, start message, start notice.

In communications systems, an audible signal transmitted by a system indicating that the system is ready to receive a message or signal. [From Weik '89]

In spread-spectrum systems, a code that is generated by summing, using modulo-two addition, the outputs of two spread-spectrum code-sequence generators. [From Weik '89]

A menu-based information searching tool that allows users to access various types of databases, such as FTP archives and white pages databases.
Note 1: Gopher is most often used as an Internet browser.
Note 2: Gopher software uses the client-server model.

That part of the cyberspace to which the user has access by means of gopher software. [2382-pt.35]
Note: The use of gopher software has declined rapidly in recent years as the use of Web software has increased.

Abbreviation for grade of service.

Acronym for Government Open Systems Interconnection Profile. A definition of Federal Government functional requirements for open systems computer network products, including a common set of Open System Interconnection (OSI) data communication protocols that enables systems developed by different vendors to interoperate and enable the users of different applications on these systems to exchange information.
Note 1: The OSI protocols were… (Read More →)

Government Emergency Telecommunications Service (GETS) is a federal government telecommunications service that currently provides National Security and Emergency Preparedness (NS/EP) users with priority voice and voiceband data communications during periods of emergency or crisis. GETS uses existing features and services of the Public Switched Network (PSN) with NS/EP augmentations and enhancements. Access is authorized to GETS using a calling card… (Read More →)

See GOSIP.

Abbreviation for general purpose interface. An equipment-interface device (usually computer equipment) with some number of digital lines, usually a multiple of eight, which may be used for input, output, or both, depending on the function.
Note: The digital lines may be individually controlled, although nothing precludes using them in combination.

Gigabit Passive Optical Network

General Packet Radio Service

Global Positioning System

Degradation of a system in such a manner that it continues to operate, but provides a reduced level of service rather than failing completely.

1. The probability of a call's being blocked or delayed more than a specified interval, expressed as a decimal fraction.
Note: Grade of service may be applied to the busy hour or to some other specified period or set of traffic conditions. Grade of service may be viewed independently from the perspective of incoming versus outgoing calls, and is not… (Read More →)

An optical fiber with a core having a refractive index that decreases with increasing radial distance from the fiber axis.
Note: The most common refractive index profile for a graded-index fiber is very nearly parabolic. The parabolic profile results in continual refocusing of the rays in the core, and compensates for multimode distortion.

In the core of an optical fiber, a plot of the variation of refractive index such that the refractive index decreases with increasing radial distance from the fiber axis.

In graphics, especially computer graphics, that which characterizes an area in which a smooth transition between one color and another, or between black and white (i.e., contrast), takes place.

Systems, including but not limited to: (a) PBX and key telephone systems, directly connected to the public switched telephone network on June 1, 1978, that may remain permanently connected thereto without registration unless subsequently modified, and (b) systems that are of the same type as those connected to the public switched telephone network on July 1, 1978, that were added… (Read More →)

Terminal equipment (other than PBX and key telephone systems) and protective circuitry connected to the public switched telephone network before July 1, 1978, that may remain connected thereto for life without registration unless subsequently modified.

1. A measure of the fineness or coarseness of definition and implementation of a System Security policy [CESG].
2. The relative fineness or coarseness by which a mechanism can be adjusted. The phrase "the granularity of a single user" means the access control mechanism can be adjusted to include or exclude any single user [TCSEC].

1. A visual representation of a character, other than a control character.
2. In the ASCII code, a character other than an alphanumeric character, intended to be written, printed, or otherwise displayed in a form that can be read by humans.
Note 1: Graphic characters are contained in rows 2 through 7 of the ASCII code table.
Note 2: The… (Read More →)

A computer environment or program that displays, or facilitates the display of, on-screen options, usually in the form of icons (pictorial symbols) or menus (lists of alphanumeric characters) by means of which users may enter commands.
Note 1: Options are selected by using the appropriate hardware (e.g., mouse, designated keyboard keys, or touchpad) to move a display cursor to, or… (Read More →)

The art or science of conveying information through the use of display media, such as graphs, letters, lines, drawings, and pictures.
Note: Graphics includes the transmission of coded images such as facsimile.

In computer science and technology, the special hardware within the computer optimized for the display of real-time 3D graphics.

A binary code in which consecutive decimal numbers are represented by binary expressions that differ in the state of one, and only one, one bit. Synonym reflected code.

An optical pattern consisting of discrete steps or shades of gray between black and white.

A circle defined by the intersection of the surface of the Earth and any plane that passes through the center of the Earth.
Note: On the idealized surface of the Earth, the shortest distance between two points lies along a great circle.

Synonym Greenwich Mean Time (GMT). Obsolete term. See Coordinated Universal Time.

Mean solar time at the meridian of Greenwich, England, formerly used as a basis for standard time throughout the world. Obsolete term. Synonym Greenwich Civil Time. See Coordinated Universal Time.

1. An electrical connection to earth through an earth-electrode subsystem.
2. In an electrical circuit, a common return path that usually (a) is connected to an earth-electrode subsystem and (b) is extended throughout a facility via a facility ground system consisting of the signal reference subsystem, the fault protection subsystem, and the lightning protection subsystem.
3. In an electrical circuit,… (Read More →)

The dissipation of rf energy by the earth.

The electrical parameters of earth, such as conductivity, permittivity, and magnetic permeability.
Note 1: The values of these parameters vary with the local chemical composition and density of the earth.
Note 2: For a propagating electromagnetic wave, such as a surface wave propagating along the surface of the Earth, these parameters vary with frequency and direction.

In the presence of an electrical fault, the current that flows in the protective ground wire of a power distribution system.

In an electrical system, an unwanted current that flows in a conductor connecting two points that are nominally at the same potential, i.e., ground, but are actually at different potentials.
Note 1: For example, the electrical potential at different points on the surface of the Earth can vary by hundreds of volts, primarily from the influence of the solar wind.… (Read More →)

An electrically conductive surface that serves as the near-field reflection point for an antenna.
Note: A ground plane may consist of a natural (e.g., Earth or sea) surface, an artificial surface of opportunity (e.g., the roof of a motor vehicle), or a specially designed artificial surface (e.g., the disc of a discone antenna).

The zero reference level used to apply and measure voltages in a system.
Note: A potential difference may exist between this reference level and the ground potential of the Earth, which varies with locality, soil conditions, and meteorological phenomena.

A method of signaling from a terminal or subscriber loop to a switch, in which method one side of a cable pair is temporarily grounded.

In radio transmission, a surface wave that propagates close to the surface of the Earth.
Note 1: The Earth has one refractive index and the atmosphere has another, thus constituting an interface that supports surface wave transmission. These refractive indices are subject to spatial and temporal changes.
Note 2: Ground waves do not include ionospheric and tropospheric waves.

The interface or transition point between the isolated and integrated ground planes. The ground window can be a dimensional area around a bus bar or the bus bar itself. After passing through the ground window, there shall be no additional paths to ground, intentional or unintentional, inside the isolated ground plane. [T1.313-1997]

1. A circuit using a common return path that is at ground potential.
Note: Earth may serve as a portion of the ground-return circuit.
2. A circuit in which there is a common return path, whether or not connected to earth.

A type of analog voicegrade access line signaling that requires the customer interface (CI) to provide a ground on the ring conductor at the network interface (NI) to initiate service requests. [T1.401-1998]

1. In frequency-division multiplexing, a specific number of associated voice channels, either within a supergroup or as an independent entity.
Note 1: In wideband systems, a group usually consists of 12 voice channels and occupies the frequency band from 60 kHz to 108 kHz.
Note 2: this is ITU-T group B (formerly CCITT group B).
Note 3: ITU-T Basic Group… (Read More →)

See facsimile.

In a communications network, a predefined address used to address only a specified set of users. Synonym collective address.

A service feature that (a) enables a controlling telephone to place a call to a specified number of telephones simultaneously, (b) enables the call to be recorded, (c) if any of the called lines is busy, enables the equipment to camp on until the busy line is free, and (d) rings the free line and plays the recorded message.

The busy hour for a given trunk group.

1. The rate of change of the total phase shift with respect to angular frequency, d/d, through a device or transmission medium, where is the total phase shift, and is the angular frequency equal to 2f, where f is the frequency.
2. In an optical fiber, the transit time required for optical power, traveling at a given mode's group velocity,… (Read More →)

In a group of waves that have slightly different individual frequencies, the time required for any defined point on the envelope (i.e., the envelope determined by the additive resultant of the group of waves) to travel through a device or transmission facility.

In frequency-division multiplexing, a distribution frame that provides terminating and interconnecting facilities at the group level, i.e., group modulator output and group demodulator input circuits of FDM carrier equipment.
Note: The basic spectrum of the FDM group is 60 kHz to 108 kHz.

In fiber optics, for a given mode propagating in a medium of refractive index , the velocity of light in vacuum, c, divided by the group velocity of the mode.
Note: For a plane wave of wavelength , the group index may also be expressed,

where n is the phase index of wavelength .

See patch bay.

1. The velocity of propagation of an envelope produced when an electromagnetic wave is modulated by, or mixed with, other waves of different frequencies.
Note: The group velocity is the velocity of information propagation and, loosely, of energy propagation.
2. In optical fiber transmission, for a particular mode, the reciprocal of the rate of change of the phase constant with… (Read More →)

Synonym blocking factor.

Network-compatible software applications that facilitate shared work on information and documents.

1. Global System for Mobility,
2. Groupe Spéciale Mobile,
3. A public all-digital cellular network using TDMA techniques for multiplexing and using a transmission band around 900 MHz. GSM formerly identified the Groupe Speciale Mobile of the European Telecommunication Standards Institute (ETSI); today it is a worldwide standard. A GSM network can provide, besides telephony services, short messaging services (SMS)… (Read More →)

General Service Subscription Management

GPON Transmission Convergence layer

In computer security, a functional unit that provides a security filter between two data processing systems operating at different security levels or between a user terminal and a database to filter out data that the user is not authorized to access. [2382-pt.8]

See frequency guard band, time guard band.

A transmission frequency that is not to be jammed or interfered with because of the value of the information being derived from it.
Note: For example, a guarded frequency will not be jammed when the tactical, strategic, and technical information that can be obtained from the transmissions outweighs the potential operational gain achieved by jamming. [From Weik '89]

Graphical User Interface

Global Unique Identifier

Synonym bound mode.

In an optical fiber, a ray that is confined primarily to the core.
Note: A guided ray satisfies the relation given by ,f21 where r is the angle the ray makes with the fiber axis, r is the radial position, i.e., radial distance, of the ray from the fiber axis, nr is the refractive index at the radial distance r… (Read More →)

A wave having (a) energy concentrated near a boundary, or between substantially parallel boundaries, separating materials of different properties and (b) a direction of propagation effectively parallel to these boundaries.

Generic User Profile