In telephony, an arrangement that uses separate leads, called the "E" lead and "M" lead, for signaling and supervisory purposes.
Note 1: The near end signals the far end by applying -48 Vdc to the "M" lead, which results in a ground being applied to the far end's "E" lead. When -48 Vdc is applied to the far end "M"… (Read More →)

See E region, ionosphere.

That portion of the ionosphere existing between approximately 95 and 130 km above the surface of the Earth.
Note: The E Region lies between the D and F regions. Synonyms Heaviside layer, Kennelly-Heaviside layer.

Abbreviation for electronic. A prefix generally indicating an association with The Internet or computerized business or office functions; e.g., an "e-file" (electronic file) or "e-commerce," (electronic commerce).

Enhanced Dolby Audio Coding 3

Enhanced Automatic Carrier Routing

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 electric E-field (transverse) polarization. Synonym E-plane bend.

Abbreviation for electronic cash. Data representing money, which data can be transferred by means of a computer network and can be traded as a token exchangeable for real money. Synonyms digicash, digital cash. [After 2382-pt.35]

Abbreviation for electronic commerce. A way of doing real-time business transactions via telecommunications networks, when the customer and the merchant are in different geographical places. [Mattila]
Note: Electronic commerce is a broad concept that includes virtual browsing of goods on sale, selection of goods to buy, and payment methods. Electronic commerce operates on a bona fide basis, without prior arrangements… (Read More →)

Ethernet Local Area Network Service

Ethernet - Local Management Interface

also E-mail, and email, Abbreviation for electronic mail. An electronic means for communication in which (a) usually text is transmitted (but sometimes also graphics and/or audio information), (b) operations include sending, storing, processing, and receiving information, (c) users are allowed to communicate under specified conditions, and (d) messages are held in storage until called for by the addressee. Some e-mail… (Read More →)

A character string that identifies, on a network, the point of presence of a user or account, and includes all information needed to direct a communication. An Internet e-mail address includes: (a) a user name that identifies a network account; (b) the channel operator @ (pronounced "at"); and (c) a domain name indicating the server computer. An e-mail address outside… (Read More →)

Synonym mail exploder.

Synonym E-bend.

Synonyme-commerce.

enhanced Voice Call Continuity

Abbreviation for electronic magazine. A periodical publication that is stored on a file server and that may be distributed or accessed via a computer network. [After 2382-pt.35]
Note: An e-zine that is distributed primarily over the Web is also referred to as a webzine.

Abbreviation for effective monopole radiated power.

In the transmission of a pulse of an electromagnetic wave representing a bit, the ratio of (a) the energy in each bit, E, to (b) the noise energy density per hertz, N.
Note: E is usually expressed in joules per bit and N is usually expressed in watts per hertz. Thus, the E/N ratio is hertz-seconds per bit. A joule… (Read More →)

End-to-end

Enhanced 9-1-1

An E9-1-1 System Service Provider (E911SSP), is typically but not always an ILEC, and provides systems and support necessary to enable 9-1-1 calling for a single or group of Public Safety Answering Points (PSAPs). In relation to the jurisdictional boundary of the PSAP and the system provider’s scope of authority, this includes:

A method of interconnection for all telecommunications providers… (Read More →)

Emergency Alert Notification

Extensible Authentication Protocol

Ethernet Automatic Protection Switching

See ground.

In satellite communications, the coverage that occurs when the satellite-to-Earth beam is sufficiently wide to cover all of the surface of the Earth exposed to the satellite, i.e., the footprint is as large as it can possibly be from a geographic standpoint.

A network of electrically interconnected rods, plates, mats, or grids, installed and connected, for the purpose of establishing a low-resistance contact with earth.

A radiocommunication service between Earth stations and one or more space stations, which may include links between space stations, in which: information relating to the characteristics of the Earth and its natural phenomena is obtained from active sensors or passive sensors on Earth satellites;
similar information is collected from airborne or Earth-based platforms;
such information may be distributed to Earth… (Read More →)

See ground.

A station located either on the Earth's surface or within the major portion of the Earth's atmosphere and intended for communication:with one or more space stations; or
with one or more stations of the same kind by means of one or more reflecting satellites or other objects in space. [NTIA] [RR] [47CFR]

In a satellite link, one of the non-orbiting communications stations that receives, processes, and transmits signals between itself and a satellite.
Note: Earth terminals may be at mobile, fixed, airborne, and waterborne Earth terminal complexes. Synonym satellite Earth terminal.

In satellite communications systems, the assembly of equipment and facilities necessary to integrate an Earth terminal into a communications network.
Note: The Earth terminal complex includes the Earth terminal and its support equipment and any required interconnect facilities and their support equipment. It does not include facilities at the site that are not necessary to establish and integrate the satellite… (Read More →)

1. Extended Area Service,
2. Emergency Alert System.

An aspect of the assessment of the effectiveness of a Target of Evaluation, namely that it cannot be configured or used in a manner which is insecure but which an administrator or end-user would reasonably believe to be secure [ITSEC].

NPA Codes that due to their unique, recognizable digit pattern (i.e., common 'B' and 'C' digit) convey certain unique knowledge re: a call to a telephone number other than the number being dialed (e.g., 800+). ERCs may be sometimes referred to as “NYY” codes to signify that N = digits 2-9 and YY = repeating digits 0-9.

Emergency Action Termination

The unauthorized interception of information-bearing emanations. [2382-pt.8]

Acronym for extended binary coded decimal interchange code. An 8-bit alphanumeric coded character set.

See signal-to-noise ratio per bit.

Abbreviation for Emergency Broadcast System.

Abbreviation for Earth coverage, electronic commerce, exchange carrier.

Abbreviation forelectronic counter-countermeasures.

1. A wave that has been reflected by a discontinuity in the propagation medium.
2. A wave that has been reflected or otherwise returned with sufficient magnitude and delay to be perceived.
Note 1: Echoes are frequently measured in dB relative to the directly transmitted wave.
Note 2: Echoes may be desirable (as in radar) or undesirable (as in telephone… (Read More →)

See scattering cross section.

In a communication circuit (4- or 2-wire) in which the two directions of transmission can be separated from each other, the attenuation of echo signals that return to the input of the circuit under consideration.
Note: Echo attenuation is expressed as the ratio of the transmitted power to the received echo power in dB.

Seeecho suppressor.

In a system, the reduction of the power level of an echo or the elimination of an echo.
Note: Echo cancellation is usually an active process in which echo signals are measured and canceled or eliminated by combining an inverted signal with the echo signal.

A check to determine the integrity of transmission of data, whereby the received data are returned to the source for comparison with the originally transmitted data. Synonym loop check.

A programming language command that causes an echo response from a computer to be displayed on a monitor or printer for analysis or monitoring of the progress of processing.

See ghost.

In computer systems, on a hard-output or display device, a line of information that verifies (reflects) data entered into the computer.

The ratio in dB of the power of a transmitted signal that is echo loss weighted (as specified in ITU-T Recommendation G.122) to the power of its reflected echo. [T1.255-1997]

The maximum echo path delay for which an echo canceler is designed to operate. [T1.508-1998]

The time in milliseconds (ms) between the incidence of a signal and the incidence of that signal's echo at a measurement point. [T1.255-1997]

See return loss.

The measurement of the depth of a body of water or the distance to an object in a body of water by measuring the time it takes sound or electromagnetic waves of known velocity to reflect from the bottom of the water body or from the distant object.
Note: In echo sounding, damped cw transmission is usually used.

The procedure by which characters entered into a system are not physically revealed [CESG].
Note: Often employed when passwords are entered so that they are not disclosed to casual observers.

A device for connection to a two-way telephone circuit to attenuate echo signals in one direction caused by signals in the other direction.

An echo check used in public switched networks operating in the full-duplex transmission mode, i.e., the two-way-simultaneous mode.

1. Electronic Countermeasures,
2. Entitlement Control Message.

Equal Cost Multipath Routing

Emergency Context Resolution with Internet Technologies

Event-Driven Architecture

Enhanced Data-Rate for GSM Evolution

In a video display, distortion that is concentrated at or near the edge of objects, and that is categorized further by its temporal and spatial characteristics.

An LED that has a physical structure superficially resembling that of an injection laser diode, operated below the lasing threshold and emitting incoherent light.
Note: Edge-emitting LEDs have a relatively small beam divergence, and thus are capable of launching more optical power into a given fiber than are the conventional surface-emitting LEDs. [After FAA]

Abbreviation for electronic document interchange. A computerized system that allows linked computers to conduct business transactions, such as invoicing and ordering, over a telecommunications network.

Abbreviation for extended-definition television.

In a URL, a domain-name suffix indicating an education institution.

End-to-End Path Protection

Electrically Erasable Programmable Read Only Memory

Energy Efficiency and Renewable Energy

End-to-End Resource Planning

Expedited Forwarding

The term "Effective 2-Wire" denotes a condition which permits the simultaneous transmission in both directions over a channel, but it is not possible to insure independent information transmission in both directions. Effective 2-wire channels may be terminated with 2-wire or 4-wire interfaces.

The term "Effective 4-Wire" denotes a condition which permits the simultaneous independent transmission of information in both directions over a channel. The method of implementing effective 4-wire transmission is at the discretion of the Access Service Provider (physical, time domain, frequency-domain separation or echo cancellation techniques).

An envelope of antenna gain contours resulting from moving the boresight of a steerable satellite beam along the limits of the effective boresight area. [NTIA] [RR]

An area on the surface of the Earth within which the boresight of a steerable satellite beam is pointed. There may be more than one unconnected effective boresight area to which a single steerable satellite beam can be pointed. [NTIA] [RR]

The average number of units of data, such as bits, characters, blocks, or frames, transferred per unit time from a source and accepted as valid by a sink.
Note: The effective data transfer rate is usually expressed in bits, characters, blocks, or frames per second. The effective data transfer rate may be averaged over a period of seconds, minutes, or… (Read More →)

The date by which routing and rating changes within the PSTN must be complete for the assigned thousands-block or the assigned CO Code. Also, the date by which the thousands-block becomes an active block. (Also referred to as “the LERG Routing Guide effective date. ”)

The radius of a hypothetical Earth for which the distance to the radio horizon, assuming rectilinear propagation, is the same as that for the actual Earth with an assumed uniform vertical gradient of atmospheric refractive index.
Note: For the standard atmosphere, the effective Earth radius is 4/3 that of the actual Earth radius.

1. The height of the center of radiation of an antenna above the effective ground level.
2. In low-frequency applications involving loaded or nonloaded vertical antennas, the moment of the current distribution in the vertical section divided by the input current.
Note: For an antenna with symmetrical current distribution, the center of radiation is the center of distribution. For an… (Read More →)

The source noise temperature in a two-port network or amplifier that will result in the same output noise power, when connected to a noise-free network or amplifier, as that of the actual network or amplifier connected to a noise-free source.
Note: If F is the noise figure numeric and 290 K the standard noise temperature, then the effective noise temperature… (Read More →)

The arithmetic product of (a) the power supplied to an antenna and (b) its gain.

For an optical fiber, the square of the product of the diameter of the near-field pattern and the sine of the radiation angle of the far-field pattern. The diameter of the near-field radiation pattern is defined here as the full width at half maximum and the radiation angle at half maximum intensity.
Note: Effective mode volume is proportional to the… (Read More →)

The product of the power supplied to the antenna and its gain relative to a short vertical antenna in a given direction. [RR]

In alternating-current power transmission and distribution, the product of the rms voltage and amperage, i.e., the apparent power, multiplied by the power factor, i.e., the cosine of the phase angle between the voltage and the current.
Note: Only effective power, i.e., the actual power delivered to or consumed by the load, is expressed in watts. Apparent power is properly expressed… (Read More →)

1. The power supplied to an antenna multiplied by the antenna gain in a given direction.
Note 1: If the direction is not specified, the direction of maximum gain is assumed.
Note 2: The type of reference antenna must be specified.
2. The product of the power supplied to the antenna and its gain relative to a half-wave dipole in… (Read More →)

Synonym effective transmission rate.

The rate at which information is processed by a transmission facility.
Note 1: The effective transmission rate is calculated as (a) the measured number of units of data, such as bits, characters, blocks, or frames, transmitted during a significant measurement time interval divided by (b) the measurement time interval.
Note 2: The effective transmission rate is usually expressed as a… (Read More →)

A property of a Target of Evaluation representing how well it provides security in the context of its actual or proposed operational use [ITSEC].

In data communications, the ratio of (a) the time to transmit a text automatically at a specified modulation rate to (b) the time actually required to receive the same text at a specified maximum error rate.
Note 1: All of the communication facilities are assumed to be in the normal condition of adjustment and operation.
Note 2: Telegraph communications may… (Read More →)

Ethernet in the First Mile

Abbreviation for electronic funds transfer. The technology that allows for funds to be transferred securely and instantaneously by electronic means from one bank account to another.

Abbreviation for enhanced graphics adapter. A display technology with pixel resolution of 640 x 350, used with early personal computers.
Note: EGA has been replaced by newer display technologies.

Abbreviation for extremely high frequency.

European Home Systems Protocol

Abbreviation for Electronic Industries Association.

Synonym dispersion-unshifted fiber.

Synonym dispersion-shifted fiber.

Any of a number of equipment interfaces compliant with voluntary industry standards developed by the Electronic Industries Association (EIA) to define interface parameters.
Note 1: Some of the EIA interface standards have been adopted by the Federal Government as Federal Standards or Federal Information Processing Standards.
Note 2: The telecommunication-standards-developing bodies of the EIA are now part of the Telecommunications… (Read More →)

European Installation Bias

A systematic and comprehensive framework that a) consists of the ingredients that make up communications infrastructure, b) includes all of these ingredients, c) specifies the 8 ingredients of environment, power, hardware, software, network, payload, ASPR (Agreements, Standards Policy and Regulations; abbreviated as Policy) and human. This framework is used for understanding and mastering vulnerabilities, identifying disciplines, decomposing attributes, preparing for… (Read More →)

A service that allows call originators to place toll telephone calls to Toll-Free Subscribers, from within specified rate areas, without a charge to the call originator. 
Note: The Toll-Free series denotes the service access codes currently of 800, 888, 877, 866, 855, 844, and 833 (As of June 3, 2017).

Excess Information Rate

Abbreviation for Extended Industry Standard Architecture. A 32-bit bus standard that supports the features of microchannel architecture and that requires a special card for 32-bit operations, while maintaining compatibility with the older ISA (Industry Standard Architecture).

Emergency Information Services Interface

Event Information Table

1. A buffer that has an adjustable capacity for data.
2. A buffer that introduces an adjustable delay of signals.

The effect produced by the existence of an electric charge, such as an electron, ion, or proton, in the volume of space or medium that surrounds it.
Note: Each of a distribution of charges contributes to the whole field at a point on the basis of superposition. A charge placed in the volume of space or in the surrounding medium… (Read More →)

1. Of a transmission medium, its length expressed as a multiple or submultiple of the wavelength of a periodic electromagnetic or electrical signal propagating within the medium.
Note 1: The wavelength may be expressed in radians or in artificial units of angular measure, such as degrees.
Note 2: In both coaxial cables and optical fibers, the velocity of propagation is… (Read More →)

A telephone in which the operating power is obtained either from a battery located at the telephone, i.e., a local battery, or from a telephone central office, i.e., a common battery.

Deprecated term. See optoelectronic.

Any one of a number of phenomena that occur when an electromagnetic wave in the optical spectrum interacts with an electric field, or with matter under the influence of an electric field.
Note 1: Two of the most important electro-optic effects having application as modulation mechanisms in optical communication are the Kerr effect and the Pockels effect, in which birefringence… (Read More →)

An optical device in which a signal-controlled element is used to modulate a beam of light.
Note 1: The modulation may be imposed on the phase, frequency, amplitude, or direction of the modulated beam.
Note 2: Modulation bandwidths into the gigahertz range are possible using laser-controlled modulators.

Intelligence information other than signals intelligence derived from the optical monitoring of the electromagnetic spectrum from ultraviolet (
0. 01 m) through the far infrared (1000 m). [JP1]

The technology associated with those components, devices and systems which are designed to interact between the electromagnetic (optical) and the electric (electronic) state. [JP1]
Note 1: The operation of electro-optic devices depends on modification of the refractive index of a material by electric fields.
Note 2: In a Kerr cell, the refractive index change is proportional to the square of… (Read More →)

Acronym for electro-optical intelligence.

Facsimile recording by means of a chemical reaction brought about by the passage of a signal-controlled current through the sensitized portion of the record sheet.

See electrostatic recording.

Nonthermal conversion of electrical energy into light.
Note 1: Electroluminescence is distinguished from incandescence, which is a thermal process.
Note 2: One example of electroluminescence is the photon emission resulting from electron-hole recombination in a pn junction, as in a light-emitting diode (LED).

Electrochemical facsimile recording in which the recorded copy is made by the passage of a signal-controlled current through an electrolyte which causes metallic ions to be deposited, thus forming an image of the object.

1. Electromagnetic compatibility is the condition which prevails when telecommunications equipment is performing its individually designed function in a common electromagnetic environment without causing or suffering unacceptable degradation due to unintentional electromagnetic interference to or from other equipment in the same environment. [NTIA]
2. The ability of systems, equipment, and devices that utilize the electromagnetic spectrum to operate in their… (Read More →)

The control of friendly electromagnetic emissions, such as radio and radar transmissions, for the purpose of preventing or minimizing their use by unintended recipients.

1. For a telecommunications system, the spatial distribution of electromagnetic fields surrounding a given site.
Note: The electromagnetic environment may be expressed in terms of the spatial and temporal distribution of electric field strength (volts/meter), irradiance (watts/meter2), or energy density (joules/meter3).
2. The resulting product of the power and time distribution, in various frequency ranges, of the radiated or conducted… (Read More →)

1. Any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics/electrical equipment. It can be induced intentionally, as in some forms of electronic warfare, or unintentionally, as a result of spurious emissions and responses, intermodulation products, and the like. [JP 1-02]
2. An engineering term used to designate interference in a piece of electronic… (Read More →)

The control of radiated and conducted energy such that emissions that are unnecessary for system, subsystem, or equipment operation are reduced, minimized, or eliminated.
Note: Electromagnetic radiated and conducted emissions are controlled regardless of their origin within the system, subsystem, or equipment. Successful EMI control with effective susceptibility control leads to electromagnetic compatibility.

The intentional insertion of electromagnetic energy into transmission paths in any manner, with the objective of deceiving operators or of causing confusion. [JP 1-02]

1. The electromagnetic radiation from a nuclear explosion caused by Compton-recoil electrons and photoelectrons from photons scattered in the materials of the nuclear device or in a surrounding medium. The resulting electric and magnetic fields may couple with electrical/electronic systems to produce damaging current and voltage surges. EMP may also be caused by non-nuclear means. [JP 1-02]
2. A broadband,… (Read More →)

Radiation made up of oscillating electric and magnetic fields and propagated with the speed of light. Includes gamma radiation, X-rays, ultraviolet, visible, and infrared radiation, and radar and radio waves. [JP 1-02]

Hazards caused by a transmitter/antenna installation that generates electromagnetic radiation in the vicinity of ordnance, personnel, or fueling operations in excess of established safe levels or increases the existing levels to a hazardous level; or a personnel, fueling, or ordnance installation located in an area that is illuminated by electromagnetic radiation at a level that is hazardous to the planned… (Read More →)

The range of frequencies of electromagnetic radiation from zero to infinity.
Note: The electromagnetic spectrum was, by custom and practice, formerly divided into 26 alphabetically designated bands. This usage still prevails to some degree. However, the ITU formally recognizes 12 bands, from 30 Hz to 3000 GHz. New bands, from 3 THz to 3000 THz, are under active consideration for… (Read More →)

The ability of a system, subsystem, or equipment to resume functioning without evidence of degradation following temporary exposure to an adverse electromagnetic environment.
Note: The system, subsystem, or equipment performance may be degraded during exposure to the adverse electromagnetic environment, but the system will not experience permanent damage, such as component burnout, that will prevent proper operation when the adverse… (Read More →)

Of an electronic circuit or device, the degree to which it is subject to malfunction or failure under the influence of electromagnetic radiation.

The characteristics of a system that cause it to suffer a definite degradation (incapability to perform the designated mission) as a result of having been subjected to a certain level of electromagnetic environmental effects. [JP 1-02]

A wave produced by the interaction of time-varying electric and magnetic fields.

Recording by means of a signal-actuated mechanical device.

Synonym bulletin board.

See e-cash.

Synonym teletraining.

See e-commerce.

That division of electronic warfare involving actions taken to ensure friendly effective use of the electromagnetic spectrum despite the enemy's use of electronic warfare.

That division of electronic warfare involving actions taken to prevent or reduce an enemy's effective use of the electromagnetic spectrum.

See EDI.

1. The deliberate radiation, reradiation, alteration, suppression, absorption, denial, enhancement, or reflection of electromagnetic energy in a manner intended to convey misleading information and to deny valid information to an enemy or to enemy electronics-dependent weapons.
Note: Among the types of electronic deception are: (a) manipulative electronic deception--Actions to eliminate revealing or convey misleading, telltale indicators that may be used… (Read More →)

In encryption, the distribution of keying materials among entities by means of an electronic communication.
Note: Electronic distribution does not include electronic key loaders, such as smart cards. [After X9.17]

1. Those measures taken to protect all transmissions from interception and electronic analysis.
2. The technical and non-technical measures taken to protect all classified non-communications electromagnetic emissions. It also takes account of the security aspects of any directly associated electromagnetic communications transmissions [CESG].

An enclosure housing telecommunications electronics equipment. It may consist of a weatherproof enclosure, equipment pad or an equipment hut. Types of equipment contained in an EEE might be switches, carrier electronics, or remote terminals. The EEE may be located remote from a central office, and may be located above or below ground. The temperature and humidity within the EEE may… (Read More →)

See EFT.

An assembly of computer hardware, software and firmware, configured for the purpose of processing, storing or forwarding information [CESG].
Note: [1] The term embraces all sorts of computer systems (with or without links to remote sites), networks and also a wide range of electronic equipment capable of processing, storing or forwarding information, including message switches, personal computers and word processors.… (Read More →)

The technical measures to ensure the security of information handled by communications, non-communications and computer systems [CESG].
Note: A general term covering COMSEC, COMPUSEC, TEMPEST and ELSEC.

Seejamming.

[An] interoperable collection of systems being developed by services and agencies of the U. S. government to automate the planning, ordering, generating, distributing, storing, filling, using, and destroying of electronic key, and management of other types of COMSEC material. [INFOSEC-99]

The path traversed by electromagnetic waves that is not subject to reflection or refraction by the atmosphere. [JP 1-02]

In facsimile, a method of scanning that provides motion of the scanning spot along the scanning line by electronic means.

See e-zine.

See e-mail.

A message system incorporating electronic mail to a central facility which then assumes responsibility for delivering the message in hard copy form.
Note: In DOD, these messages have a specific format known as message text format (MTF). Synonym [loosely] messaging service.

[A] service providing interpersonal messaging capability; meeting specific functional, management, and technical requirements; and yielding a business-quality electronic mail [e-mail] service suitable for the conduct of official government business. [INFOSEC-99] Synonym messaging service.

Software and hardware interfacing merchants and credit-card authorization networks. [Mattila]

The Electronic Program Guide (EPG) is a means of presenting or querying information about the available content to the consumer, allowing interactive selection of desired content. Synonymous with Interactive Program Guide (IPG).

The process of creating messages, distributing them, and reproducing them entirely online, often with a capability for feedback.
Note: Unlike desktop publishing, electronic publishing does not usually generate hardcopy.

The detection, identification, evaluation, and location of foreign electromagnetic radiations emanating from other than nuclear detonations or radioactive sources. [JP 1-02]

The ESE defines the system in security terms, identifying boundaries of security significance. These boundaries may be: a. internal, i.e., security partitions within the system, or b. external, i. e. manual or electronic interfaces to the LSE or the GSE (e. g. terminals, printers or communications lines to other systems) [CESG].

Synonym equilibrium mode distribution.

1. A telephone switching system based on the principles of time-division multiplexing of digitized analog signals.
Note: An electronic switching system digitizes analog signals from subscribers' loops, and interconnects them by assigning the digitized signals to the appropriate time slots. It may also interconnect digital data or voice circuits.
2. A switching system with major devices constructed of semiconductor components.… (Read More →)

The part of e-commerce (electronic commerce) software that processes real-time credit card payments. [After Mattila]

A Web-browser plug-in that handles and stores a user's credit card and payment information. [Mattila]

Any military action involving the use of electromagnetic and directed energy to control the electromagnetic spectrum or to attack the enemy. The three major subdivisions within electronic warfare are: electronic attack, electronic protection, and electronic warfare support. [After JP1]

1. That division of electronic warfare involving actions taken under direct control of an operational commander to search for, intercept, identify, and locate sources of radiated electromagnetic energy for the purpose of immediate threat recognition. Thus, electronic warfare support measures (ESM) provide a source of information required for immediate decisions involving electronic countermeasures (ECM), electronic counter-countermeasures (ECCM), avoidance, targeting, and… (Read More →)

The coupling of a lightwave from one dielectric waveguide into another dielectric waveguide upon the application of an electric field or electrical signal.
Note: Devices that perform ECC can be used as switches.

[A] key generated in a COMSEC device by introducing (either mechanically or electronically) a seed key into the device and then using the seed, together with a software algorithm stored in the device, to produce the desired key. [INFOSEC-99]

Technical and geolocation intelligence information derived from foreign noncommunications electromagnetic radiations emanating from other than nuclear detonations or radioactive sources. [JP 1-02]

1. Protection resulting from measures designed to deny unauthorized persons information derived from the interception and analysis of noncommunications electromagnetic radiations. [INFOSEC-99]
2. The protection resulting from all measures designed to deny unauthorized persons information of value that might be derived from their interception and study of noncommunications electromagnetic radiations, e.g., radar. [JP 1-02]

Recording in which light is used to produce a change in electrostatic charge distribution to form a photographic image.
Note: Subsequent processing is usually required to make the image visible.

Recording in which an electrical signal is directly impressed on the record medium.

The rapid, spontaneous transfer of electrostatic charge induced by a high electrostatic field. Usually the charge flows through a spark (static discharge) between two bodies at different electrostatic potentials as they approach one another. [T1.321-1995]

Having the capability of dissipating or limiting the generation of electrostatic charge, or of providing shielding from electrostatic discharges or electrostatic fields. [T1.321-1995]

The electric field produced by an electrostatic charge. [T1.308-1996]

Recording by means of a signal-controlled electrostatic field.
Note: Subsequent processing is usually required to make the image visible.

A barrier or enclosure that attenuates an electrostatic field. [T1.321-1995]

That type of recording produced principally by signal-controlled thermal action.

In facsimile transmission systems, any segment of a scanning line, the dimension of which along the line is exactly equal to the nominal line width.
Note: An elemental area is not necessarily the same as the scanning spot.

See unit interval.

An atmospheric duct consisting of a high-density air layer that starts at high altitudes and continues upward or remains at high altitudes, thus affecting primarily very-high-frequency (VHF) transmission. [From Weik '89]

Abbreviation for extremely low frequency.

Emergency Location Identification Number

Acronym for electronics intelligence.

In cryptology and within particular elliptic curve parameters, a statistically unique and unpredictable integer in the interval [1, n - 1], where n is the prime order of the base point G. [After X9.62]

In cryptography, given particular elliptic curve parameters (and an elliptic curve private key d), the elliptic curve point Q = dP. [After X9.62]

In electromagnetic wave propagation, polarization such that the tip of the electric field vector describes an ellipse in any fixed plane intersecting, and normal to, the direction of propagation.
Note 1: An elliptically polarized wave may be resolved into two linearly polarized waves in phase quadrature with their polarization planes at right angles to each other. [2196]
Note 2: Circular… (Read More →)

Enhanced LORAN

Acronym for electronics security.

The protection resulting from all measures designed to deny unauthorized persons information of value that might be derived from intercept and analysis of compromising emanations from other than crypto-equipment and telecommunications systems.

1. In Web page design, to link or to insert an inline video image or sound file into the page so that it is hyperlinked and clickable.
2. In a Web page, an HTML tag indicating an embedded object in a Web page.

Modulation achieved using algorithms that quantize the difference between the input and the estimated signal into core bits and enhancement bits. [T1.310-1991]

Customer-premises equipment that had been provided by the Bell Operating Companies prior to January 1, 1984, that was ordered transferred from the BOCs to AT&T by court order.

[A] computer system that is an integral part of a larger system. [INFOSEC-99]

[A] cryptosystem performing or controlling a function as an integral element of a larger system or subsystem. [INFOSEC-99]

Cryptography engineered into an equipment or system whose basic function is not cryptographic. [INFOSEC-99]

Telephone-company-provided premises equipment in use or in inventory of a regulated telephone utility as of divestiture (December 31, 1983).

A channel provided on telecommunications facilities to support administration and maintenance. For primary rate access, the EOC is the extended superframe (ESF) data link. [T1.408-1990]

In non-ADP equipment, a CPU and firmware that are critical to the operation of the equipment.
Note: An embedded processor is not subject to FIRMR regulation when used for control of devices such as weapons systems, communications devices, home appliances, automobile diagnostics, etc.

Abbreviation for electromagnetic compatibility.

Analysis of a system, subsystem, facility, or equipment to determine its electromagnetic compatibility (EMC) status.
Note: The EMC analysis may be theoretical analysis before construction or an empirical analysis after construction.

Abbreviation for emission control.

Abbreviation for equilibrium mode distribution.

Abbreviation forelectromagnetic environment.

The EATF supports session continuity (e.g., Handover) of an emergency call initially established using IMS when movement of the UE requires a change of access network from packet network (e.g., LTE) to circuit network (e.g., GSM or UMTS).

A national public warning system that, together with other emergency notification mechanisms, is part of an overall national public alert and warning system under the jurisdiction of the Federal Emergency Management Agency (FEMA), an agency of the Department of Homeland Security. EAS is a newer version of a national public warning system that replaced the Emergency Broadcast System (EBS) in… (Read More →)

The EBS is composed of AM, FM, and TV broadcast stations; low-power TV stations; and non-Government industry entities operating on a voluntary, organized basis during emergencies at national, state, or operational (local) area levels. [47CFR]

A functional element in a NENA i3 system that uses the LoST protocol [RFC 5222] where location information (either civic address or geo-coordinates) and a Service URN serve as input to a mapping function that returns a URI used to route an emergency call toward the appropriate PSAP or responding agency based on the caller’s location. See CLEI™ Code. (CLEI™… (Read More →)

A modified changeover procedure that is used whenever the normal changeover procedure cannot be used because of failure(s) in the signaling terminal equipment or inaccessibility between the two involved signaling points. [T1.226-1992]

A transmitter of an aircraft or survival craft actuated manually or automatically that is used as an alerting and locating aid for survival purposes. [NTIA] [RR]

A station in the mobile service the emissions of which are intended to facilitate search and rescue operations. [NTIA] [RR]

A web site intended for information sharing by the Federal Response Plan (FRP) community.

A special attendant position used to terminate emergency calls. It provides sufficient signaling and display capabilities to support the functionality of routed, bridged and transferred emergency calls. [After T1.628-1993]

A call identified as receiving emergency service treatment. The call has an associated CESID (caller's emergency service ID), bridging, and transfer numbers. [T1.628-1993]

A 3-5 digit number that represents one or more ESZs, and is defined as one of two types: Administrative ESN or Routing ESN.

A 3-5 digit number that represents one or more ESZs, and is defined as one of two types: Administrative ESN or Routing ESN.

The ESQK identifies a 911 call instance processed through a VoIP Positioning Center (VPC). An ESQK is associated with a Selective Router/Emergency Service Number combination. The ESQK is used to route the call and is delivered to the PSAP as the calling number/ANI for the call, and is subsequently used by the PSAP to request ALI information for the call.… (Read More →)

The first exchange in the call connection capable of invoking the routing portion of the RBTESC service. This may be a local exchange or a transit exchange. It recognizes the emergency call and determines the caller's emergency service zone (ESZ), the transfer number(s), and the priority of the call. [T1.628-1993]

An i3 functional element which is a SIP proxy server that selects the next hop routing within the ESInet based on location and policy. There is an ESRP on the edge of the ESInet. There is usually an ESRP at the entrance to an NG9-1-1 PSAP. There may be one or more intermediate ESRPs between them.

A local exchange that is capable of invoking the bridging and transfer portions of the RBTESC (routing, bridging and transfer of emergency service calls) service. The served user is directly connected to this exchange. [T1.628-1993]

A geographical area within the emergency service serving area in which all callers are served by the same set of emergency service agencies. [T1.628-1993]

A geographical area that represents a unique combination of emergency service agencies (e.g., Law Enforcement, Fire and Emergency Medical Service) within a specified 9-1-1 governing authority’s jurisdiction. An ESZ is represented by an Emergency Service Number (ESN) to identify the ESZ.

A managed IP network that is used for emergency services communications, and that can be shared by all public safety agencies. It provides the IP transport infrastructure upon which independent application platforms and core functional processes can be deployed, including, but not restricted to, those necessary for providing NG911 services. ESInets may be constructed from a mix of dedicated and… (Read More →)

A 10-digit number used for the purpose of routing an E911 call to the appropriate Public Service Answering Point (PSAP) when that call is originating from wireless equipment. The Emergency Services Routing Digit (ESRD) identifies the cell site and sector of the call origination in a wireless call scenario. The Emergency Services Routing Key (ESRK) uniquely identifies the call in… (Read More →)

A period of not more than 72 consecutive hours (the aggregate of which do not exceed 15 days per year) during which emergency calls and services are expedited by emergency response teams. [After T1.304-1989]

Emergency Telecommunications Service (ETS) is a national service, providing priority telecommunications to the ETS-authorized user in times of disaster and emergency (ITU-T Study Group 2) [ITU-T E.107].

The E-CSCF receives the emergency session establishment request from a P-CSCF (in an IMS originating network) or the I-CSCF in an IMS-based NG9-1-1 Emergency Services Network), queries the LRF for routing information, and forwards the call request toward the appropriate PSAP or other emergency services network per the routing information.

1. electromagnetic interference,
2. Exchange Message Interface.

1. Electromagnetic energy propagated from a source by radiation or conduction.
Note: The emission may be either desired or undesired and may occur anywhere in the electromagnetic spectrum.
2. Radiation produced, or the production of radiation, by a radio transmitting station. For example, the energy radiated by the local oscillator of a radio receiver would not be an emission but… (Read More →)

The selective and controlled use of electromagnetic, acoustic, or other emitters to optimize command and control capabilities while minimizing, for operations security (OPSEC): (a) detection by enemy sensors; (b) to minimize mutual interference among friendly systems; and/or (c) to execute a military deception plan. [After JP1]

Protection resulting from measures taken to deny unauthorized persons information derived from intercept and analysis of compromising emanations from crypto-equipment or an information system (IS). [INFOSEC-99] Synonym [in INFOSEC] emissions security.

Of a radio emission, the distribution of power or energy as a function of frequency.

See emission security.

The ratio of power radiated by a substance to the power radiated by a blackbody at the same temperature.

1. Expected Measured Loss,
2. Element Management Layer.

Entitlement Management Message

Extensible MultiModal Annotation Language

Abbreviation for emotion icon. In electronic communication, a multi-character symbol, created with ASCII characters, to express emotions and physical characteristics that would normally be communicated by body language and facial expressions in face-to-face communication.
Note: Emoticons are most often used in informal e-mail messages and newsgroup postings and are usually designed to be viewed sideways. Some examples of emoticons are:… (Read More →)

Abbreviation for electromagnetic pulse.

In FM transmission, the intentional alteration of the amplitude-vs. -frequency characteristics of the signal to reduce adverse effects of noise in a communication system.
Note: The high-frequency signal components are emphasized to produce a more equal modulation index for the transmitted frequency spectrum, and therefore a better signal-to-noise ratio for the entire frequency range.

A number assigned by a service provider for its own internal business purposes. See “Administrative Numbers“ definition.

Abbreviation for electromagnetic radiation.

Abbreviation for electromagnetic radiation hazards.

1. Electronic Message System,
2. Element Management System.

Acronym foremanations security.

Emergency Telecommunications

To duplicate the functions of one system with a different system, so that the second system appears to behave like the first system.
Note: For example, a computer emulates another, different computer by accepting the same data, executing the same programs, and achieving the same results.

Abbreviation for electromagnetic vulnerability.

Enterprise Network

Signaling in which address digits are transmitted in one or more blocks, each block containing sufficient address information to enable switching centers to carry out progressive onward routing.

When applied to privilege: a privilege that is active, i.e., has its effective flag set [POSIX.6].

A signal that permits the occurrence of an event.

In open systems, the technique used by layered protocols in which a lower layer protocol accepts a message from a higher layer protocol and places it in the data portion of a frame in the lower layer.

1. [To] Convert plain text into an unintelligible form by means of a cipher. [NIS]
2. [To] convert plain text to cipher text by means of a cryptographic system. [INFOSEC-99]

The cryptographic transformation of data (see cryptography) to produce ciphertext [7498-2]. Note Encipherment may be irreversible, in which case the corresponding decipherment process cannot feasibly be performed.

1. To convert data by the use of a code, frequently one consisting of binary numbers, in such a manner that reconversion to the original form is possible.
2. [To] Convert plain text to cipher text by means of a code. [INFOSEC-99]
3. To append redundant check symbols to a message for the purpose of generating an error detection and… (Read More →)

See analog-to-digital converter.

See analog encoding.

A law defining the relative values of the quantum steps used in quantizing and encoding signals.

1. [A] generic term encompassing encipher and encode. [INFOSEC-99]
2. To convert plain text into unintelligible forms by means of a cryptosystem.
Note: The term encrypt covers the meanings of encipher and encode. [JP1-02]

See encipherment [7498-2]

1. In cryptography, a set of mathematically expressed processes for rendering information into apparently meaningless form by developing a series of transformations to the normal representation of the information through the use of variable elements controlled by the use of a key. [After X9.65]
2. [A] set of mathematically expressed rules for rendering data unintelligible by executing a series of… (Read More →)

A group of contiguous characters to be encrypted. [After X9.23]

The last certificate considered in a certificate chain.

In start-stop teletypewriter operation, the shifting of the end of all marking pulses, except the stop pulse, from their proper positions in relation to the beginning of the next start pulse.
Note 1: Shifting of the end of the stop pulse is a deviation in character time and rate rather than an end distortion.
Note 2: Spacing end distortion is… (Read More →)

1. In cryptography, a certificate subject that (a) uses its private key for purposes other than signing certificates, or (b) uses its public key for purposes other than signing certificates. [After X.509]
2. The subject of the final certificate in a certification path, i.e., that subject which is not a certificate authority. [After X9.5]

Synonym end office.

For an optical fiber, the optical quality of the surface at the end of the fiber.

A communication device that is connected to the terminals of a circuit.

A central office at which user lines and trunks are interconnected. Synonym end exchange.

A system containing the application processes that are the ultimate source and sink of user traffic.
Note: The functions of an end system can be distributed among two or more processors or computers.

1. The ultimate user of a telecommunications service.
2. A person in contact with a Target of Evaluation who makes use only of its operational capacity [ITSEC].

A control character that may be used to identify either the physical end of a data medium or the end of the usable or used portion of a data medium. [From Weik '89]

In tape relay procedure, the letter and key functions, including the end-of-message indicator, that constitute the last format line.

The character that indicates the end of the selection signal.

A transmission control character used to terminate text.

A transmission control character used to indicate the conclusion of a transmission that may have included one or more texts and any associated message headings.
Note: An EOT is often used to initiate other functions, such as releasing circuits, disconnecting terminals, or placing receive terminals in a standby condition.

A transmission control character used to indicate the end of a transmission block of data when data are divided into such blocks for transmission purposes.

A direct peer to peer communication of terminal equipment (TE) to TE, or TE to a network gateway supporting, for example, PSPDN interworking (public switched packet data network interworking). [T1.606-1990]

1. A characteristic of preserving the privacy and/or unadulterated nature of communicated data across networks which may include, e.g., application relays in store-and-forward or chained applications.
2. The capability that the application relay should be able to forward data (or parts thereof) as received at the relay without needing to completely decode/decrypt that data. (See also ISO/IEC
1074
5. )… (Read More →)

Encipherment of data within or at the source end system, with the corresponding decipherment occurring only within or at the destination end system. (See also link-by-link encipherment. ) [7498-2]

[The] encryption of information at its origin and decryption at its intended destination without intermediate decryption. [INFOSEC-99]

1. Safeguarding information in a secure telecommunication system by cryptographic or protected distribution system means from point of origin to point of destination. [NIS]
2. Safeguarding information in an information system (IS) from point of origin to point of destination. [INFOSEC-99]

The capability changeover procedure to be used whenever the normal one cannot be accomplished (i.e., in case of some failure in the signaling terminal equipment or in case of inaccessibility between the two involved signaling points). [T1.110-1987]

In network topology, a node connected to one and only one yybranch. Synonym peripheral node.

The property of a system, subsystem, equipment, or process that enables it to continue to function within specified performance limits for an extended period of time, usually months, despite a severe natural or man-made disturbance, such as a nuclear attack, or a loss of external logistic or utility support.
Note: Endurability is not compromised by temporary failures when the local… (Read More →)

See endurability.

Synonym orderwire circuit.

Synonym orderwire circuit.

A system that establishes connections between customer installations (CIs) and constituent public service access points (PSAPs), provides automatic location information (ALI), and has provisions for selective routing. [T1.414-1998]

Service, offered over commercial carrier transmission facilities used in interstate communications, that employs computer processing applications that act on the format, content, code, protocol, or similar aspects of the subscriber's transmitted information; provides the subscriber with additional, different, or restructured information; or involves subscriber interaction with stored information.

A company that provides, via a connection to an exchange carrier, services that add value to voice and/or data information. [T1.251-1996]

Synonym [in ITU-T usage] improved-definition television.

Abbreviation for enquiry character.

A transmission control character used as a request for a response from the station with which a connection has been set up.
Note: The response may include station identification, the type of equipment in service, and the status of the remote station.

The OSI term for a layered-protocol machine.

The entrance to a building for both public and private network service cables (including antenna transmission lines, where applicable), including the entrance point at the building wall or floor, and continuing to the entrance room or entrance space. [After ANSI/TIA/EIA-568A]

In a building, the point of emergence of telecommunications service cables through an exterior wall, floor slab, or from a rigid metal conduit or intermediate metal conduit. [After ANSI/TIA/EIA-568A]

In a building, a space in which the joining of inter- and/or intrabuilding telecommunications backbone facilities takes place.
Note: An entrance room may serve also as an equipment room. [After ANSI/TIA/EIA-568A]

1. In cryptosystems, the deliberate planting of apparent flaws in a data processing system for the purpose of detecting attempted penetrations or for confusing an intruder about which flaws to exploit. [2382-pt.8]
2. [The] deliberate planting of apparent flaws in an information system (IS) for the purpose of detecting attempted penetrations. [INFOSEC-99]

E.164 NUmber Mapping

The boundary of the family of curves obtained by varying a parameter of a wave. See figure under amplitude modulation.

Signal distortion that results when the rate of change of phase shift with frequency over the necessary bandwidth of the signal is not constant.
Note: Envelope delay distortion is usually expressed as one-half the difference between the delays of the two extremes of the necessary bandwidth.

See air-conditioning.

1. The security that is inherent in the physical surroundings in which a facility or functional unit is located, such as on ships, on aircraft, and in underground vaults, where locations by their nature provide a certain amount of protection against exploitation of compromising emanation even before other protective measures are implemented.
2. The application of electrical, acoustic, physical, and… (Read More →)

Abbreviation for end office.

Abbreviation for end-of-transmission character.

Abbreviation for engineering orderwire.

Electronic Product Code

Enhanced Packet Data Interworking Function

Electronic Program Guide

A electronic or hard-copy table or listing of the predicted positions of astronomical bodies such as the planets or the Moon; and by extension, the predicted positions of artificial satellites, such as communications satellites, orbiting the Earth. Plural ephemerides.
Note 1: Ephemerides are essential tools for accurate aiming of movable high-gain antennas at, e.g., communications satellites, especially ones that exhibit… (Read More →)

A date in history, chosen as the reference date from which time is measured.
Note 1: An example of an epoch date is the beginning instant of January 1, 1900, Universal Time, for Transmission Control Protocol/Internet Protocol (TCP/IP).
Note 2: TCP/IP programs exchange date or time-of-day information with time expressed as the number of seconds past the epoch date.

Ethernet Passive Optical Network

Extensible Provisioning Protocol

Enhanced Primary Reference Time Clock

Include only initial incremental presubscription costs and initial incremental expenditures for hardware and software related directly to the provision of equal access which would not be required to upgrade the switching capabilities of the office involved absent the provisions of equal access. [47 CFR Pt.36-A]

A diversity combiner in which the signals on each channel are added.
Note: The channel gains can be made to remain always and everywhere equal so that the resultant signal remains approximately constant.

The term "Equal Level Echo Path Loss" (ELEPL) denotes the measure of Echo Path Loss (EPL) at a 4-wire interface which is corrected by the difference between the send and receive Transmission Level Point (TLP). [ELEPL = EPL - TLP (send) + TLP (receive)].

A telegraph or a data code in which (a) all the words or code groups are composed of the same number of unit elements, (b) each element has the same duration or spatial length, (c) each word or code group has the same duration or spatial length, and (d) usually each word or code group has the same number of… (Read More →)

An analog patching facility at which all nominal input and output voice frequency levels are uniform.
Note: The use of an equal-level patch bay permits patching without making transmission level adjustments.

The maintenance of system transfer function characteristics within specified limits by modifying circuit parameters.
Note: Equalization includes modification of circuit parameters, such as resistance, inductance, or capacitance.

For a satellite orbiting the Earth, an orbit in the equatorial plane.
Note: An equatorial orbit has an inclination angle of 0°.

Synonym equilibrium length.

For a specific excitation condition, the length of multimode optical fiber necessary to attain equilibrium mode distribution.
Note: Equilibrium length is sometimes used to refer to the longest such length, as would result from a worst-case, but undefined, excitation. Synonyms equilibrium coupling length, equilibrium mode distribution length.

That condition in a multimode fiber wherein after propagation has taken place for a certain distance, called the "equilibrium length," the relative power distribution among modes becomes statistically constant and remains so for the course of further propagation down the fiber.
Note 1: In practice, the equilibrium length may vary from a fraction of a kilometer to more than a… (Read More →)

Synonym equilibrium length.

Synonym equilibrium mode distribution.

For an optical fiber, a device or optical system used to create an approximation of the equilibrium mode distribution.

A clock that satisfies the particular needs of equipment and, in some cases, may control the flow of data at the equipment interface.

See CLEI™ Code.

(CLEI™ is a trademark of iconectiv, LLC. )

Intermodulation noise introduced into a system by a specific piece of equipment.

In a building, a centralized space for telecommunications equipment that serves the occupants of the building.
Note: An equipment room is considered distinct from a telecommunications closet because of the nature or complexity of the equipment housed by the equipment room. [After ANSI/TIA/EIA-568A]

The portion of a device that is directly connected to facilities internal to a station, such as the data terminal equipment (DTE) side of the DTE/data-circuit-terminating (DCE) interface, switches, and user end instruments.

A mass, or bonded masses, of conducting material that offer a negligible impedance to current flow.
Note: Equipotential ground planes may be in direct contact with the earth or may be physically isolated from the earth and suitably connected to it.

An implementation-defined relation between the values of MAC labels or of Information Labels. Two labels are equivalent if each of the labels dominates the other [POSIX.6].

A standard cross section of cable conductors for use in equating the metallic content of cable conductors of all gauges to a common base. [47 CFR Pt.36-A]

1. In a system, a network that may replace another network without altering the performance of the system.
2. A network with external characteristics that are identical to those of another network.
3. A theoretical representation of an actual network.

A quantitative representation in resistance units of the spectral density of a noise-voltage generator, given by Rn = (Wn)/(kT0), where Wn is the spectral density, k is Boltzmann's constant, T0 is the standard noise temperature (290 K), and kT0 =
4. 00 × 10-21 watt-seconds.
Note: The equivalent noise resistance in terms of the mean-square noise-generator voltage, e2, within a… (Read More →)

The temperature, usually expressed in kelvins, of a hypothetical matched resistance at the input of an assumed noiseless device, such as a noiseless amplifier, that would account for the measured output noise. [From Weik '89]

The product of sheath kilometers and the number of equivalent gauge pairs of conductors in a cable. [47 CFR Pt.36-A]

The amount of thermal noise power on a frequency-division multiplexed (FDM) or wire channel necessary to approximate the same judgment of speech quality created by quantizing noise in a PCM channel.
Note 1: The speech quality judgment is based on comparative tests.
Note 2: Generally,
3
3. 5 dBrnC ±
2. 5 dB is considered the approximate equivalent PCM noise… (Read More →)

The noise temperature referred to the output of the receiving antenna of the Earth station corresponding to the radio-frequency noise power which produces the total observed noise at the output of the satellite link excluding noise due to interference coming from satellite links using other satellites and from terrestrial systems. [NTIA] [RR]

The product of (a) the length of a section of cable in kilometers (sheath kilometers) and (b) the ratio of the metallic content applicable to a particular group of conductors in the cable (e.g., conductors assigned to a category) to the metallic content of all conductors in the cable. [47 CFR Pt.36-A]

Abbreviation for emergency response link.

1. To obliterate information from a storage medium, such as to clear or to overwrite.
2. In a magnetic storage medium, to remove all stored data by (a) changing the medium to an unmagnetized state or (b) changing the medium to a predetermined magnetized state.
3. In paper tape and punched card storage, to punch a hole at every punch… (Read More →)

[A] process intended to render magnetically stored information irretrievable by normal means. [INFOSEC-99]

In frequency-division multiplexing, a position of a translated channel in which an increase signal frequency in the untranslated channel causes an increase signal frequency in the translated channel. Synonym upright position.

Emergency Response Location

A dimensionless unit of the average traffic intensity (occupancy) of a facility during a period of time, usually a busy hour.
Note 1: Erlangs, a number between 0 and 1, inclusive, is expressed as the ratio of (a) the time during which a facility is continuously or cumulatively occupied to (b) the time that the facility is available for occupancy.… (Read More →)

1. Effective Radiated Power,
2. Enterprise Resource Planning.

A block in which there are one or more erroneous bits.

1. The difference between a computed, estimated, or measured value and the true, specified, or theoretically correct value.
2. A deviation from a correct value caused by a malfunction in a system or a functional unit.
Note: An example of an error is the occurrence of a wrong bit caused by an equipment malfunction.

In video, a form of block distortion where one or more blocks in the image bear no resemblance to the current or previous scene and often contrast greatly with adjacent blocks. [After T1.80
1. 02-1996]

The bit-error-ratio requirement allocated to the respective segments of a communications system, such as trunking, switching, access, and terminal devices, in a manner that satisfies the specified system end-to-end bit-error-ratio requirement for transmitted traffic.

A contiguous sequence of symbols, received over a data transmission channel, such that the first and last symbols are in error and there exists no contiguous subsequence of m correctly received symbols within the error burst.
Note: The integer parameter m is referred to as the guard band of the error burst. The last symbol in a burst and the… (Read More →)

In the receipt and processing of digitized television transmissions, a method of covering up errors from dropouts by using the redundancy in most adjacent-frame image information.
Note: Video images are frequently nearly identical from frame to frame. Adjacent video lines frequently have almost the same detail. It becomes possible, therefore, when a "burst error" involving the modification or loss of… (Read More →)

Any technique that will detect or correct errors.

In the reception or processing of digital data, the use of overhead bits and appropriate algorithms to detect, and within certain constraints, restore a corrupted data stream or block with a high degree of confidence.
Note 1: In addition to applications having to do with conventional data processing and storage, error correction can be used in specialized applications such as… (Read More →)

In a computer or communications system, a message that indicates that an error has been made and, sometimes, the nature or type of error. [From Weik '89]

Deprecated term. See error ratio.

The ratio of the number of bits, elements, characters, or blocks incorrectly received to the total number of bits, elements, characters, or blocks sent during a specified time interval.
Note: For a given communication system, the bit error ratio will be affected by both the data transmission rate and the signal power margin.

In computer and communications systems, an audio or visual signal that indicates that an error has been made by the system or its operator.
Note: In most systems, the error signal accompanies an error message and is used to draw operator attention to the error message. [From Weik '89]

A code in which each telegraph or data signal conforms to specific rules of construction so that departures from this construction in the received signal can generally be automatically detected and corrected.
Note 1: If the number of errors is less than or equal to the maximum correctable threshold of the code, all errors will be corrected.
Note 2: Error-correcting… (Read More →)

In digital data transmission, a system employing either forward error correction (FEC) or automatic repeat-request (ARQ) techniques such that most transmission errors are automatically removed from the data unit prior to delivery to the destination facility.

A code in which each telegraph or data signal conforms to specific rules of construction, so that departures from this construction in the received signal can generally be detected automatically.
Note: Error-detecting codes require more signal elements than are necessary to convey the basic information.

A system employing an error-detecting code and so arranged that any signal detected as being in error is either deleted from the data delivered to the data sink, in some cases with an indication that such deletion has taken place, or delivered to the data sink together with an indication that the signal is in error.

Synonym ARQ.

A 1-yysecond interval in which no errored blocks are received.
Note: In general, measurement is over time and is stated as a percentage, i.e., % EFS. [T1.514-1995]

1. A 1-yysecond period with one or more errored blocks.
2. A 1-second interval with one or more bit errors.
Note 1: Severely errored seconds (SES) are defined as a subset of ES.
Note 2: A period of loss of signal is considered as a period of errored blocks. [T1.514-1995]

A specified period of time, during which bits are transferred from a source to a destination, that contains at least one bit in error. Examples of an errored unit of time are an errored second (ES), and a severely errored second. [After T1.507-1996]

1. End System,
2. Expert System,
3. Errored-Second.

Enhanced Subscriber Authentication

Enterprise Service Bus

Abbreviation for escape character.

1. In alphabet coding schemes, a specially designated character, the occurrence of which in the data signifies that one or more of the characters to follow are from a different character code, i.e., have meanings other than normal.
2. In a text-control sequence of characters, a control character that indicates the beginning of the sequence and the end of any… (Read More →)

An indicator consisting of one or more digits which is defined in a given numbering plan and is used to indicate that the digits that follow are from a specific numbering plan which is different from the given number plan.
Note: An escape code can be carried forward through the originating network and can be carried across internetwork and international… (Read More →)

Abbreviation for electrostatic discharge.

Abbreviation for extended superframe.

Emergency Services Interconnection Forum

Abbreviation for electronic warfare support measures.

Emergency Services Messaging Interface

Emergency Services Network

Emergency Services Network Interfaces

1. Ethernet Service Provider,
2. Encapsulating Security Payload,
3. Enhanced Subscriber Privacy.

Abbreviation for electronic switching system.

A network-provided service feature in which a priority dial tone is furnished.
Note 1: Essential service is typically provided to fewer than 10 % of network users.
Note 2: Essential service is recommended for use in conjunction with NS/EP telecommunications services. Synonym critical service.

Abbreviation for end-of-transmission-block character.

A standard protocol (IEEE
80
2. 3) for a 10-Mb/s baseband local area network (LAN) bus using carrier-sense multiple access with collision detection (CSMA/CD) as the access method, implemented at the Physical Layer in the ISO Open Systems Interconnection--Reference Model, establishing the physical characteristics of a CSMA/CD network.
Note 1: Ethernet is a standard for using various transmission media, such… (Read More →)

1. Enhanced Telecom Operations Map,
2. Enhanced Telecommunications Operations Map.

Emergency Telecommunications Service

A number priority level from one to five where one has the highest priority for ETS. (Legacy GETS or, WPS, or NGN-PS) services and five has the lowest priority for ETS (Legacy GETS or, WPS, or NGN-PS) services. The Service User’s priority level for WPS is assigned to a Service User. Defined by the Federal Communications Commission in Report &… (Read More →)

European Telecommunications Standards Institute

Abbreviation for end-of-text character.

End-system Unique Identifier

1. Assessment of an information technology (IT) product or system against defined security-related functional and assurance criteria, performed by a combination of testing and analytic techniques.
2. The detailed examination of a system or a product to search for vulnerabilities and to determine the extent to which the required or claimed security functions are upheld by its implementation [CESG].
Note:… (Read More →)

One of seven increasingly rigorous packages of assurance requirements from CC (Common Criteria) Part
3.
Note: Each numbered package represents a point on the CC's predefined assurance scale. An EAL can be considered a level of confidence in the security functions of an IT (information-technology) product or system. [After CC'99]

Documentation that formally defines the security functions of a system or product against which its evaluation is performed [CESG].
Note: A System Electronic Information Security Policy forms the basis of the evaluation baseline for a system.

Report issued by a CLEF to report any problem, other than those already covered by an SFN, relating to the Target of Evaluation (TOE). Initial distribution should be to the UK Certification Body [CESG]. See also: Security Fault Notification.

An organization working directly for CESG whose purpose is to perform evaluations [CESG].

1. Member of an Evaluation Facility assigned to a particular evaluation [CESG].
2. The independent person or organization that performs an evaluation [ITSEC].

A component of the evaluation criteria for a particular phase or aspect of evaluation, identifying what the evaluator must do to check the information supplied by the sponsor of the evaluator, and the additional activities he must perform [ITSEC].

In a waveguide, a time-varying field having an amplitude that decreases monotonically as a function of transverse radial distance from the waveguide, but without an accompanying phase shift.
Note 1: The evanescent field is coupled, i.e., bound, to an electromagnetic wave or mode propagating inside the waveguide.
Note 2: The evanescent field is a surface wave.
Note 3: In fiber… (Read More →)

A mode of the evanescent field.

Ethernet Virtual Connection

Evolution Data Optimized

See parity, parity check.

1. An occurrence or happening, usually significant to the performance of a function, operation, or task.
2. In Integrated Services Digital Networks (ISDN), an instantaneous occurrence that changes at least one of the attributes of the global status of a managed object.
Note: An event (a) may be persistent or temporary, thus allowing for functions, such as surveillance, monitoring, and… (Read More →)

Enhanced Variable Rate Codec

Abbreviation for electronic warfare.

A method of receiving either amplitude- or phase-modulated signals in which method the carrier is separated from the sidebands, filtered and amplified, and then combined with the sidebands again at a higher level prior to demodulation. Synonym reconditioned carrier reception.

In data transmission, the condition assumed by a device when it receives a command that it cannot execute.

Deprecated term. See insertion loss.
Note: Excess insertion loss was used to indicate that, in an optical-fiber coupler, the loss occasioned by dividing the input power among the ports is not the total insertion loss.

1. A room or building equipped so that telephone lines terminating there may be interconnected as required.
Note: The equipment may include manual or automatic switching equipment.
2. In the telephone industry, a geographic area (such as a city and its environs) established by a regulated telephone company for the provision of local telephone services.
3. In the Modification of… (Read More →)

In telephone networks, access in which exchange services are provided for originating or terminating interexchange telecommunications within the exchange area.

A geographic area served by one or more central offices within which local telephone service is furnished under regulation.

Information exchanged between a claimant and a verifier during the process of authenticating a principal.

1. A carrier authorized to provide telecommunication services within one or more access service areas. [T1.104-1988]
2. A company that provides telecommunications within a LATA (United States) or province (Canada). In Canada, ECs also provide telecommunications among Canadian carriers. [T1.209-1998]

A unique four-character alphabetic code that identifies the legal company name shall be assigned, as appropriate, to represent each exchange carrier.

The facilities included within a local access and transport area.

Synonym subscriber line.

This is a combination of (a) exchange cable and wire facilities (b) exchange central office circuit equipment, including associated land and buildings and (c) information origination/termination equipment which forms a complete channel. [47 CFR Pt.36-A]

1. (or . exe)
1. A filename extension identifying executable code.
2. An identifying extension for a form of self-extracting archive. [Bahorsky]

Synonym supervisory program.

One of several states in which an information system (IS) may operate, and the only one in which certain privileged instructions may be executed. Such privileged instructions cannot be executed when the system is operating in other (e.g., user) states. Synonym supervisor state. [INFOSEC-99]

An organization, activity, or person included in the collective address group of a message and deemed by the message originator as having no need for the information in the message.
Note: Exempted addressees may be explicitly excluded from the collective address group for the particular message to which the exemption applies.

[A] key used exclusively to safeguard communications transmitted over the air during military or organized civil training exercises. [INFOSEC-99]

A trial-and-error attempt to violate computer security by systematically attempting to use a very large number of possible passwords or keys. [After 2382-pt.8] Synonym [loosely] brute-force attack.

Synonym [in ITU-T usage] distribution-quality television.

A device that restores the dynamic range of a compressed signal to its original dynamic range.

The restoration of the dynamic range of a compressed signal to its original dynamic range.

The inherent limit for increasing the capacity of a system beyond its installed capacity.

The term "Expected Measured Loss" denotes a calculated loss which specifies the end-to-end 1004-Hz loss on a terminated test connection between two readily accessible manual or remote test points. It is the sum of the inserted connection loss and test access loss including any test pads.

In layered systems, a service data unit that is delivered to a peer entity in the destination open system before the delivery of any subsequent service data unit sent on that connection.

A station utilizing radio waves in experiments with a view to the development of science or technique. This definition does not include amateur stations. [NTIA] [RR]

A computer system that facilitates solving problems in a given field or application by drawing inference from a knowledge base developed from human expertise.
Note 1: The term "expert system" is sometimes used synonymously with "knowledge-based system," although it is usually taken to emphasize expert knowledge.
Note 2: Some expert systems are able to improve their knowledge base and develop… (Read More →)

A message generated by the network and sent to the user terminal to indicate a congestion condition. [T1.615-1992]

Services that can be accessed from an application program, via an API, and are generally provided only when requested [POSIX.0].

Synonym mail exploder.

1. [A] Channel that allows the violation of the security policy governing an information system (IS) and is usable or detectable by subjects external to the trusted computing base. [INFOSEC-99]
2. Any channel that is usable or detectable by subjects external to the Trusted Computing Base.

Any outside plant facilities subject to the effects of lightning; or to power contacts, power induction, or differences in ground potential any of which exceed 300 Vrms to ground. [T1.316-1997]

In INFOSEC, the potential compromise associated with an attack exploiting a corresponding vulnerability. [2382-pt.8]

A permanently connected voice circuit between selected stations for technical control purposes.

An ACL that contains other entries in addition to the required entries [POSIX.6].

A network-provided service feature in which a user pays a higher flat rate to obtain wider geographical coverage without paying per-call charges for calls within the wider area.

See EBCDIC.

In T-carrier, a synchronization frame that delineates 24 DS1 frames
Note: ESF requires less frequent synchronization than the T-carrier D-4 superframe format. This frees overhead bits for on-line, real-time testing, and monitoring of circuit parameters. ESF also facilitates nonchannelized operation and clear-channel operation.

Television in which (a) improvements are made to the standard National Television System Committee (NTSC) television system, (b) the improvements are receiver-compatible with the standard NTSC television system, and (c) the improvements modify the standard NTSC television system emission standards.
Note 1: EDTV improvements may include (a) a wider aspect ratio, (b) a higher picture definition than NTSC definition, and… (Read More →)

A property of a system, format, or standard that allows changes in performance or format within a common framework, while retaining partial or complete compatibility among systems that belong to the common framework. [FCC ACATS]

See XML.

In telephony, a user end device, separate from a subscriber telephone, which device produces an audible signal indicating that there is an incoming call from a switchboard or exchange. [From Weik '89]

The first bit of each octet of the address field of a packet. The first octet is identified by the extension bit set to 0, and the second octet is identified by the extension bit set to
1. [T1.312-1991]

A facility that provides access to communications for a user or group of users isolated from a central communications node.

A terminal that is added to an existing terminal and that uses the same circuit and address, i.e., port and number, as the terminal to which it is added.

A set of external entities to the application platform with which information is exchanged. External entities include people, exchangeable media that is not mounted in the platform, communication wiring, and all other platforms [POSIX.0].

The interface between the application platform and the external environment across which information is exchanged. The External Environment Interface is defined primarily in support of system and application interoperability. The primary services present at the External Environment Interface comprise: Human/Computer Interaction Services, Information Services, Communication Services [POSIX.0].

In a given communications system, a timing reference obtained from a source, such as a navigation system, external to the given system.
Note: External timing references are usually referenced to Coordinated Universal Time .

A plug-in, add-on, or helper application used with a Web browser to present graphics, audio, or video files.
Note: For example, an external-viewer program could allow the presentation of nonstandard graphics and audio files.

The sum of the absorption coefficient and the scattering coefficient. [From Weik '89]

The ratio of two optical power levels, of a digital signal generated by an optical source, e.g., a laser diode, where P1 is the optical power level generated when the light source is "on," and P2 is the power level generated when the light source is "off. "
Note: The extinction ratio may be expressed as a fraction or in… (Read More →)

Synonym added bit.

Synonym added block.

In information assurance, a sector that is written on a diskette track in excess of the standard number of sectors, as part of a method of copy protection. [2382-pt.8]

In information assurance, a track that is written on a diskette in excess of the standard number of tracks, as part of a method of copy protection. [2382-pt.8]

[The] capability of crypto-equipment or secure telecommunications equipment to resist efforts to extract [the] key. [INFOSEC-99]

An intranet that has been extended to include access to or from selected external organizations such as customers or suppliers, but not the general public.
Note: Connections may be via leased lines, dial-up connections, or network interconnections. The overall network may be, but is not necessarily, a virtual private network. [After 2382-pt.35]

Frequencies from 30 GHz to 300 GHz. See electromagnetic spectrum.

Frequencies from 30 Hz to 300 Hz. See electromagnetic spectrum.

For an optical fiber, that portion of a joint loss that is not intrinsic to the fibers, e.g., loss caused by end separation, angular misalignment, or lateral misalignment.

An oscilloscope display in which a pseudorandom digital data signal from a receiver is repetitively sampled and applied to the vertical input, while the data rate is used to trigger the horizontal sweep.
Note: System performance information can be derived by analyzing the display. An open eye pattern corresponds to minimal signal distortion. Distortion of the signal waveform due to… (Read More →)

A message marker for a special-category message that is intended for delivery only to a specific person, or authorized representative of that person, and therefore no one else. [From Weik '89]