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See F region.
- Browse Related Terms: absorption, absorption band, absorption index, Absorptivity, F layer, material absorption, path loss, phonon absorption, Photoelectric Effect, photovoltaic effect, sudden ionospheric disturbance (SID)
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- That portion of the ionosphere existing between approximately 160 and 400 km above the surface of the Earth, consisting of layers of increased free-electron density caused by the ionizing effect of solar radiation. Note 1: The F region reflects normal-incident frequencies at or below the critical frequency (approximately 10 MHz) and partially absorbs waves of higher frequency. Note 2: The F1 layer exists from about 160 to 250 km above the surface of the Earth and only during daylight hours. Though fairly regular in its characteristics, it is not observable everywhere or on all days. The principal reflecting layer during the summer for paths of 2,000 to 3,500 km is the F1 layer. The F1 layer has approximately 5 ÃÂ 105 e/cm3 (free electrons per cubic centimeter) at noontime and minimum sunspot activity, and increases to roughly 2 ÃÂ 106 e/cm3 during maximum sunspot activity. The density falls off to below 104 e/cm3 at night. Note 3: The F1 layer merges into the F2 layer at night. Note 4: The F2 layer exists from about 250 to 400 km above the surface of the Earth. The F2 layer is the principal reflecting layer for HF communications during both day and night. The horizon-limited distance for one-hop F2 propagation is usually around 4,000 km. The F2 layer has about 106 e/cm3. However, variations are usually large, irregular, and particularly pronounced during magnetic storms.
- Browse Related Terms: F Region, flutter, meteor burst communications, near-vertical-incidence skywave, power margin, propagation mode, radio fadeout, reflecting layer, reflecting loss, reflection, skip distance, skip zone, sky wave, Sporadic E, traveling wave, tropospheric scatter, tropospheric wave
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In laser diodes, a phenomenon in which a high field intensity of stimulated optical radiation causes degradation of the facets, i.e., those forming the cavity mirrors, decreasing reflectivity and resulting in a decrease of the internal quantum efficiency and an increase in the threshold current.
- Browse Related Terms: active laser medium, facet erosion, optical disk, Raman scattering, spontaneous emission, Stimulated Emission, superluminescent LED, superradiance, threshold current
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A fixed, mobile, or transportable structure, including (a) all installed electrical and electronic wiring, cabling, and equipment and (b) all supporting structures, such as utility, ground network, and electrical supporting structures. 2. A network-provided service to users or the network operating administration. 3. A transmission pathway and associated equipment. 4. In a protocol applicable to a data unit, such as a block or frame, an additional item of information or a constraint encoded within the protocol to provide the required control. 5. A real property entity consisting of one or more of the following: a building, a structure, a utility system, pavement, and underlying land. [JP1]
- Browse Related Terms: aggregator, automatic ringdown circuit, B channel, Block Holder, compatibility testing, exchange access, facility, maintenance, MJU, network administration, number portability, open video systems, pair-gain system, point code (PC), positioned interface structure, second dialtone, service bit, service integrity, service signals, service-provider portability, system services API, terminal service profile (TSP), Toll Free Service End-User Subscriber, verified off-hook
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A group of interconnected equipment and transmission media uniquely identified and dedicated to a specific type of service. [T1.238-1994/97]
- Browse Related Terms: access provider, card session, facility assembly, fixed access, multimedia communication system, NIC, non-fixed access, PCS application, PCS session, PCS switching center, Personal Communications Service, point of access, protection switching (PS), record, seizing
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A two-digit code (FC) used in the exchange-carrier-to-interexchange carrier (EC-to-IC) facility/service selective signaling protocol and the IC-to-EC facility/service selective signaling protocol that identifies the type of facility requested. [T1.104-1991]
- Browse Related Terms: acceptance limit (AL), access service area, exchange carrier (EC), facility code, other common carrier (OCC), point of presence (POP), point of termination (POT), public switched network (PSN), service code, specialized common carrier (SCC), switched exchange access network, tariff, teletext, viewdata, wireline common carrier
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The electrically interconnected system of conductors and conductive elements that (a) provides multiple current paths to the earth electrode subsystem, and (b) consists of the earth electrode subsystem, the lightning protection subsystem, and the fault protection subsystem.
- Browse Related Terms: air terminal, facility grounding system, fault protection subsystem, neutral ground
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The particular group of facilities to route the call. [T1.667-1999]
- Browse Related Terms: access channel, access function, application entity (AE), application service element (ASE), basic call process (BCP), call control function (CCF), call segment, carrier selection, connection control, connectionless service, facility group, feature code, monitor window, network access point (NAP), network data, network interworking, network operator, network provider, originating line information (OLI), physical plane, plain old telephone service (POTS), plane, point in call (PIC), recipient, route index, route list, service control, service independence, service logic, service management access function (SMAF), service node (SN), service subscriber (SS), service switching and control point (SSCP), service switching function (SSF), service switching point (SSP), serving area ID, single point of control, single-ended service feature, terminal type
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The specific member of a trunk group or a multi-line hunt group. [T1.667]
- Browse Related Terms: endurable operation, facility group member, persistent data, trunk hunting
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In a facsimile receiver, a device that changes the signal modulation from frequency-shift keying (FSK) to amplitude modulation (AM). 2. In a facsimile transmitter, a device that changes the signal modulation from amplitude modulation (AM) to frequency-shift keying (FSK).
- Browse Related Terms: baseband, black facsimile transmission, black recording, Carson bandwidth rule, center frequency, facsimile converter, maximum modulating frequency, non-return-to-zero (NRZ), out-of-band emission, picture frequency, software defined radio, white facsimile transmission
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- A form of telegraphy for the transmission of fixed images, with or without half-tones, with a view to their reproduction in a permanent form. [47CFR] In this definition the term telegraphy has the same general meaning as defined in the Convention. [NTIA] [RR] 2. The process by which fixed graphic images, such as printed text and pictures, are scanned, and the information converted into electrical signals that may be transmitted over a telecommunications system and used to create a copy of the original, or an image so produced. Note 1: Wirephoto and telephoto are facsimile via wire circuits. Radiophoto is facsimile via radio. Note 2: Technology now exists that permits the transmission and reception of facsimile data to or from a computer without requiring hard copy at either end. Note 3: Current facsimile systems are designated and defined as follows:
- Group 1 Facsimile: The mode of black and white facsimile operation, defined in ITU-T Recommendation T.2, that uses double sideband modulation without any special measures to compress the bandwidth. Note 1: A 216 à279-mm document, i.e., an 8ý à11-inch document, may be transmitted in approximately 6 minutes via a telephone-type circuit. Additional modes in this group may be designed to operate at a lower resolution suitable for the transmission of 216 à279-mm documents in 3 to 6 minutes. Note 2: The CCITT frequencies used are 1300 Hz for white and 2300 Hz for black. The North American standard is 1500 Hz for white and either 2300 or 2400 Hz for black.
- Group 2 Facsimile: The mode of black and white facsimile operation, defined in ITU-T Recommendation T.3, that accomplishes bandwidth compression by using encoding and vestigial sideband, but excludes processing of the document signal to reduce redundancy. Note: A 216 à279-mm document, i.e., an 8ý à11-inch document, may be transmitted in approximately 3 minutes using a 2100-Hz AM/PM/VSB, over a telephone-type circuit.
- Group 3 Facsimile: The mode of black and white facsimile operation, defined in ITU-T Recommendation T.4, that incorporates means for reducing the redundant information in the signal by using a one-dimensional run-length coding scheme prior to the modulation process. Note 1: A 216 à279-mm document, i.e., an 8ý à11-inch document, may be transmitted in approximately 1 minute or less over a telephone-type circuit with twice the Group 2 horizontal resolution. The vertical resolution may also be doubled. Note 2: Group 3 Facsimile machines have integral digital modems. Note 3: An optional two-dimensional bandwidth compression scheme is also defined within the Group 3 Facsimile Recommendation. Note 4: When any CCITT or CCIR Recommendation is modified by the ITU-T, the modified document is designated as an ITU-T Recommendation.
- Group 3C Facsimile: The Group 3 digital mode of facsimile operation defined in ITU-T Recommendation T.30. Note: Group 3C is also referred to as Group 3 Option C or as Group 3-64 kb/s.
- Group 4 Facsimile: The mode of black and white facsimile operation defined in ITU-T Recommendation T.563 and CCITT Recommendation T.6. Note 1: Group 4 Facsimile uses bandwidth compression techniques to transmit, essentially without errors, a 216 à279-mm document, i.e., an 8ý à11-inch document, at a nominal resolution of 8 lines/mm in less than 1 minute over a public data network voice-grade circuit. Note 2: When any CCITT or CCIR Recommendation is modified by the ITU-T, the modified document is designated as an ITU-T Recommendation.
- Type I Facsimile: The mode of digital black and white facsimile operation defined in MIL-STD-188-161 used for transmission of bi-level information (e.g., text and simple graphics). Note: Type I facsimile is interoperable with the black-and-white facsimile mode of STANAG 5000 and is designed for operation over noisy communications links such as tactical channels.
- Type II Facsimile: The mode of gray-scale facsimile operation defined in MIL-STD-188-161 used for transmission of multi-level information (e.g., photographs). Note: Type II facsimile is interoperable with the black-and-white facsimile mode of Type I or STANAG 5000 equipment and is designed for operation over noisy communications links such as tactical channels.
- Browse Related Terms: clock, embedded processor, facsimile (FAX), master clock, Plenum, Radio Regulations, turnkey
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At any point in a frequency-shift facsimile system, the numerical difference between the frequency that corresponds to a white signal and the frequency that corresponds to a black signal. Note: Facsimile frequency shift is usually expressed in hertz. [From Weik '89]
- Browse Related Terms: amplitude-vs.-frequency distortion, attenuation distortion, balanced code, blue noise, channel offset, chip time, continuous wave (cw), facsimile frequency shift, protected frequency, single-frequency interference, slope, spot jamming, transition frequency, twist
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In facsimile systems, the baseband signal that results from the scanning process.
- Browse Related Terms: aspect ratio, available line, Compression Ratio, cooperation factor, facsimile picture signal, facsimile transmitter, nominal linewidth, pel, phasing, PIXEL, radio baseband, scanning, solid-state scanning, underlap, white signal
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In a facsimile system, the equipment that converts the facsimile picture signal into a recorded copy.
- Browse Related Terms: aperture distortion, characters per inch (cpi), continuous tone copy, contouring, facsimile receiver, facsimile recorder, photosensitive recording, record medium, recording spot, reproduction speed, spot speed, Stagger, start-record signal, stop-record signal
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In a facsimile receiver, the device that performs the final conversion of the facsimile picture signal to an image of the object, i.e., makes the recorded copy.
- Browse Related Terms: aperture distortion, characters per inch (cpi), continuous tone copy, contouring, facsimile receiver, facsimile recorder, photosensitive recording, record medium, recording spot, reproduction speed, spot speed, Stagger, start-record signal, stop-record signal
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In a facsimile system, the signal level at any point in the system. Note 1: The facsimile signal level is used to establish the operating levels. Note 2: The facsimile signal level is usually expressed in dB with respect to some standard value, such as 1 mW (milliwatt), i.e., 0 dBm.
- Browse Related Terms: Bias, bit error ratio tester (BERT), carrier level, facsimile signal level, peak signal level, primary radar, quantizing levels, received signal level (RSL), reference system, reference transmission level point, secondary radar, signal level, signal-to-crosstalk ratio, singing margin, system loading
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In a facsimile system, the equipment that sends and receives facsimile signals. Note: Full-duplex facsimile transceivers can send and receive at the same time; half-duplex facsimile transceivers cannot.
- Browse Related Terms: analog facsimile equipment, confirmation to receive, facsimile transceiver, FAX, noisy black, noisy white, radio detection, receive loudness rating (RLR), run-length encoding, signal contrast, transcoding, transmission time
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In a facsimile system, the equipment that converts the baseband picture signals, i.e., the baseband signals resulting from scanning the object, into signals suitable for transmission by a communications system.
- Browse Related Terms: aspect ratio, available line, Compression Ratio, cooperation factor, facsimile picture signal, facsimile transmitter, nominal linewidth, pel, phasing, PIXEL, radio baseband, scanning, solid-state scanning, underlap, white signal
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1. In signal propagation, see fading. 2. In video, the act of dissolving a video picture to either a color, pattern, or titles. Note: Fading a video image is often used as an artistic tool in video productions, usually seen as a fade to black. 3. In audio, a decrease in the sound level until it is no longer audible.
- Browse Related Terms: bitmap, bits per pixel (BPP), black burst, chroma keying, chroma noise, chrominance, chrominance signal, color balancing, color bar test signal, color bars, color decoder, color phase, color processing, color subcarrier, color-difference signal, colorimetry, complementary colors, composite video signal, Continuous Tone, contrast, fade, masking, reference color space, tristimulus values
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A design allowance that provides for sufficient system gain or sensitivity to accommodate expected fading, for the purpose of ensuring that the required quality of service is maintained. 2. The amount by which a received signal level may be reduced without causing system performance to fall below a specified threshold value. Synonym fading margin.
- Browse Related Terms: Active Sensor, bandwidth compression, carrier synchronization, channel-associated signaling, equal gain combiner, fade margin, polarization diversity, Receiver, request-repeat (RQ) signal, request-to-send signal, ringdown circuit, selective fading, signal sample, spectral purity, transmitter, transparent loopback