FIBER OPTIC CENTER GLOSSARY

View: Glossary, Acronyms, Military Specifications for Connectors

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There are 208 names in this directory beginning with the letter D.
D TYPE
A description for the 9, 15 and 25 pin connectors widely used for data communications and microcomputer peripherals. It looks very loosely like a "D" when viewed vertically.

D-1 Format
A serial digital recording format.

D-2 Format
A composite digital recording format.

D-3 Format
A composite digital recording format.

D-Block Carrier
A 10-MHz personal-communications-services carrier serving a basic trading area in the 1865-to-1870-MHz band paired with the 1945-to-1950-MHz band.

D-CHANNEL
Delta/Data Channel. A sort of status line in the ISDN arena. A 16 Kbps line carrying control signals and call data in the BRI interface. A 64 Kbps line in the PRI interface.

D4
D4 connectors are made from a 2.5mm diameter ceramic (zirconia) ferrule for durability and one of the older generation connectors which is keyed, and spring loaded and has a 2mm diameter ferrule.

Daisy Chain
Connections in series that render all of the connections common.

Dark fiber
An unused fiber installed for future use.

Data communications
The transmission of data from one point to another.

Data communications equipment (DCE)
A device, typically a modem, used in RS-232 data networks.

Data compression
A mathematical technique that encodes data so that it uses less space (bandwidth) during transmission or storage.

Data encryption
A mathematical technique that encodes data so that it is more secure during transmission or storage. The data must be decrypted for use.

Data Grade Circuit
A telephone line capable of carrying high-speed data. The line is specially conditioned to accommodate this.

Data Link
1) The physical means of connection one location to another for the purpose of transmitting and receiving data.  2) Synonymous with communication link.

Data Link Layer
Layer 2 of the Open Systems Interconnect (OSI) model; it defines protocols governing data packetizing and transmission into and out of each node.

Data Service Unit
DSU. A device for transmitting data on digital transmission facilities. Sometimes incorporated with a CSU.

Data Set
Another term for modem.

Data terminal equipment (DTE)
Used with RS-232 data equipment, DTE is a specific pinout configuration on standard RS-232 DB9 or DB25 connectors. Usually a DTE device is a terminal with a male connector; its complementary device (DCE) normally has a female connector.

Data Transmission
The conveying of data from one place for reception elsewhere by signals transmitted over a data circuit.

dB
(1) Abbreviation for decibel; (2) The loss of a signal in a conductor expressed in decibels, denoting the ratio of the power input to output; (3) One tenth of a bel.

dB Loss
The loss of a signal in a conductor expressed in decibels.

dB/km
A logarithmic unit describing the ratio of loss of power per kilometer distance. These values are always referenced to a specific wavelength, e.g., 0.35 dB/km at 1310 nm, and are used by fiber and cable manufacturers to define the optical fiber’s attenuation.

DB15
A standardized connector with 15 pins for Ethernet transceivers.

DB25
A standardized connector with 25 pins for parallel or serial connections.

DB9
A standardized connector with nine pins for token ring and serial connections.

dBc
Decibel Carrier

dBd
Decibel Dipole

dBi
Decibel Isotropic

dBm
Decibels relative to one milliwatt. A positive number indicates the power is above one milliwatt; a negative number indicates the power is below. This unit has become common in fiber optic communication systems because the power of light sources used with optical fibers is on the order of one milliwatt.

DC
Direct current. Current which moves in a single direction in a steady flow. Normal household electricity is alternating current (AC) which repeatedly reverses its direction. However, many electronics devices require DC, and therefore must convert the current into DC before using it.

DC Resistance
Provides an effective check on cable and connector integrity. Both cabling and connectors have inherent DC resistance. Loop resistance is the combined resistance of each individual wire in a two-wire pair. It is tested for each pair by placing a known DC voltage on one wire in the pair, shorting the Remote Handset and reading the voltage loss at the Display Handset. DC loop resistance testing is essential to isolating poor connector punch downs, cable damage and shorts.

DCS-1800
1) Digital Cordless Standard 1800. 2) Digital Communications Service 1800 MHz is an upbanded variant of the Global System for Mobile Communications.

Dead Face
The term which describes the various methods used to protect contacts when not engaged.

Dead Front
Mating surfaces of a connector designed so that the contacts are recessed below the surface of the connector insulator body to prevent accidental short-circuiting of the contacts.

Deadweight
The largest weight of cargo, bunkers and stores a ship is able to carry. Expressed in metric tons (1000 kg) or long tons (1016 kg). The deadweight tonnage is the most important commerical measurement. Normally the maximum payload for a ship is three to ten percent lower than the deadweight, due to the weight of bunkers and stores, etc.

Deadzone
An area where an OTDR cannot make measurements. It is limited by the laser’s pulse width, the reflection of the front panel connector, and detector circuitry. The shorter the pulse width, the shorter the deadzone.

Deadzone box
A package with internal fiber that is used to test fiber spans with an OTDR, allowing attenuation and connector reflectance to be measured within the OTDR’s dead zone. The internal fiber must be at least 20 times the OTDR’s minimum pulse width, and they are most commonly sold in lengths of 500 or 1,000 meters.

Deceleration Stress
Additional stress imposed on a wire rope due to decreasing the velocity of the load

Decibel (dB)
1)A unit of measurement to express logarithmic differences of power level. It is used to express power gain in amplifiers or power loss in passive circuits or components. Expressed as dB.  2)A unit to express differences of power level. A term that expresses two power levels used to indicate gains or losses in a system.

Decibel/kilometer (dB/km)
A unit of measurement for fiber optic attenuation.

Decoder
1) A device used to separate the individual component portions of a composite signal.  2) A device the decodes scrambled television broadcast signals.

Defect
Any non-conformance with the normally accepted characteristics of a part.

Degradation
A gradual deterioration in performance.

degree of polymerization
the number of monomeric units in a macromolecule or oligomer molecule. (IUPAC)

Delamination
The separation of layers in a laminate because of failure of the adhesive, either in the adhesive itself or at the interface between the adhesive and the adherend.

Delay Line
1) A device used to delay a signal for a specified length of time. 2) A cable made to provide very low velocity of propagation with long electrical delay for transmitted signals.

Delay Skew
The difference in propagation delay between any two pairs within the same cable sheath. Also known as Propagation Delay/Delay Skew. Delay Skew is a measurement of the signaling delay difference from the fastest pair to the slowest. Delay Skew is calculated from Propagation Delay measurements.

Delayed Strain
See latent strain.

Demarcation point
The point of interconnection between telephone company terminal equipment and a building’s wiring where the operational control or ownership changes.

Demodulation
The process of separating the information signal from the carrier signal.

Demultiplexer (Demux)
A device that separates the two or more signals that have been combined into a multiplexed signal. An optical demultiplexer separates signals at different wavelengths. An electronic demultiplexer separates signals that have been electronically multiplexed by time (TDM) or frequency (FDM).

Denier
Unit of measure for the linear mass density of fibers. It is defined as the mass in grams per 9000 meters.

Dense wavelength division multiplexing (DWDM)
A method of increasing the amount of data that can be transmitted over an optical fiber.

Density
Ratio of weight (mass) to volume of a material – ie grams per cubic centimeter or pounds per gallon.

Depolarization of scatter light
The phenomenon, due primarily to the anisotropy of the polarizability of the scattering medium, resulting from the fact that the electric vectors of the incident and scattered beams are not coplanar and that, therefore, light scattered from a vertically (horizontally) polarized incident beam contains a horizontal (vertical) component. (IUPAC)

Depolymerization
Separation of a complex molecule into simple molecules; also softening of a sealant by the same action.

Depressed-clad optical fiber
The inner cladding, next to the core, has a lower index of refraction than the outer cladding region. Depressed refers to the IR mismatch between the two claddings, resulting in a small MFD that reportedly fusion splices more readily but tends to be more sensitive to the bending losses encountered in most enclosures.

Depth of Crimp
Thickness of the crimped portion of a connector measured between two opposite points on the crimped surface. The distance the indentor penetrates into the barrel. (MIL-STD)

Derating Factor
A factor used to reduce the current carrying capacity of a wire when used in environments other than that for which the value was established.

Design Factor
In a wire, the ratio of the minimum break strength to the total working load. Typical ratio is 5:1, but standards vary based upon industry, environment, and application

Destructive Test
See test, destructive.

Detector
A device that picks up light from fiber and converts the information into an electrical signal. A device such a photodiode or photodetector that converts optical energy into electrical energy. They can be made from silicon, germanium, gallium arsenide, indium gallium arsenide or from other semiconductors, depending on the wavelengths to detect. The positive-intrinsic-negative (PIN) and the avalanche photodiode (APD) types are used in fiber optics. PIN types can be used for analog or digital systems, while APDs with their internal amplification can only be used in digital systems.

Detector-amplifier
A device in which an optical detector is packaged with electronic amplification circuitry.

Device-Under-Test (DUT)
The cable, harness, or other assembly that is being tested by the cable tester.

Device, As Related to a Work Station
An item such as a telephone, personal computer, or graphic or video terminal.

Device, As Related to Protection
A protector, a protector mount, a protector unit or a protectomodule.

Dewetting
A situation where a lead was at one point in the soldering process wetted by the solder, but due to extended time or temperature, the presence of intermetallics, volatiles or other causes, has become withdrawn from the wetted surface.

Dextrin
A water based product derived from the acidification and/or roasting of starch.

DIACID
A molecule with two carboxylic acid (-COOH) functional groups

Diameter
Distance measured across the center of a circle circumscribing the wires of a strand or the strands of a wire rope

DIAMINE
A molecule with two amine (-NH2) functional group

Diamond Lapping Film
Diamond lapping films cut and polish the hard ceramic ferrules and the softer fibers close to the same rate, easily controlling fiber undercut or protrusion. Diamond also helps assure the ferrule geometries meet the Telcordia GR 326 version 3 specifications, and leave the ferrule in a condition ready for the final polish film. Diamond is always recommended for the intermediate steps of machine polishing of single mode or multimode ceramic connectors, and for single mode hand polishing of ceramic connectors. When stopping at a diamond of 1um or less, a good surface finish results with great geometries, but with a return loss of -35 dB at best. If back reflection of -55 dB or better is required, see our Final Polish Films.

Die Closure
The gap between indenter dies at full handle closure. Usually defined by Go/No-Go dimensions.

Dielectric
A nonconducting or insulating material that resists passage of electric current.  1) A material having electrical insulating properties. (MIL-STD)  2) Any insulating material between two conductors which permits electrostatic attraction and repulsion to take place across it.  3) A non-conducting material or a material having the property that the energy required to establish an electric field is recoverable, in whole or in part, as electric energy. A vacuum is a dielectric.

Dielectric Breakdown (DWV)
The voltage required to cause an electrical failure or breakthrough of the insulation. The insulation barrier is insufficient and only a small air gap keeps metal conductors from shorting. When high voltage is applied, the tester detects the weak insulation through an electrical arc (electricity flowing through the insulation).

Dielectric Cable
A nonconducting cable, such as fiber optic cable, without metallic members.

Dielectric Constant
Also called permittivity. That property of a dielectric which determines the amount of electrostatic energy that can be stored by the material when a given voltage is applied to it. Actually, the ratio of the capacitance of a capacitor using the dielectric to the capacitance of an identical capacitor using a vacuum as a dielectric.

Dielectric Constant (K)
The ratio of the capacitance of a condenser with dielectric between the electrodes to the capacitance when air is between the electrodes. Also called Permittivity and Specific Inductive Capacity (SIC).

Dielectric Constant (Permittivity)
1)The ratio of the capacitance using the material in question as the dielectric, to the capacitance resulting when the material is replaced by air.  2)That property of a dielectric which determines the electrostatic energy stored per unit volume for a unit potential gradient. The ratio of the capacitance using the material in question as the dielectric, to the capacitance resulting when the material is replaced by air. The dielectric constant is the most important design parameter for coaxial cables and determines dimensions, losses and propagation characteristics.

Dielectric Curing
The use of a high frequency electric field through a joint to cure a synthetic thermosetting adhesive; a curing process for wood and other nonconductive joint materials.

Dielectric Heating
The heating of an insulating material when placed in a radio-frequency field, caused by internal losses during the rapid polarization reversal of molecules in the material.

Dielectric Loss
Power dissipated in an insulating medium as the result of the friction caused by molecular motion when an AC Electric field is applied. In a coaxial cable, the losses caused by the transformation of electromagnetic energy into heat within the dielectric material.

Dielectric Loss Factor (Dielectric Loss Index)
A measure of the loss characteristics of a dielectric material.

Dielectric Strength
1)The voltage which an insulation can withstand before breakdown occurs. Usually expressed as a voltage gradient (such as volts per mil).  2)The maximum voltage that a dielectric material can withstand, under specified conditions. without rupturing. Usually expressed as a voltage gradient such as volts per mil.

Dielectric Test
A test in which a voltage higher than the rated voltage is applied for a specified time to determine the adequacy of the insulation under normal conditions. Sometimes called a "Hi-Pot" test (high potential).

Dielectric Withstanding Voltage
The maximum potential gradient that a dielectric material can withstand without failure.

Differential group delay (DGD)
A delay caused by different arrival times of optical signals, which results in modal dispersion. In multimode fibers, DGD is the delay difference of the various modes. In single-mode fibers, DGD is the delay caused by chromatic, waveguide, and polarization mode dispersion.

Diffraction
Phenomenon that results when light passes by an opaque edge or through an opening, generating weaker secondary wavefronts. These secondary wavefronts interfere with the primary wavefronts as well as with each other to form various patterns.

Diffraction Grating
An array of fine, parallel, equally-spaced reflecting or transmitting lines that mutually enhance the effects of diffraction to concentrate the diffracted light in a few directions determined by the spacing of the lines and by the wavelength of the light.

Digital
(1) Pertaining to the utilization of discreet integral numbers in a given base to represent all the quantities that occur in a problem or a calculation. It is possible to express in digital form all information stores, transferred or processed by a dual-state condition; e.g., on-off, open-closed and true-false. (2) Compare with analog.

Digital Advanced Mobile Phone System (DAMPS)
Digitally-enhanced AMPS based on the ID-54 standard. Also referred to as TDMA.

Digital Cordless Telephone US (DCTU)
A version of Digital European Cordless Telecommunications proposed for the US personal-communications-services market.

Digital European Cordless Telecommunications (DECT)
DECT is a digital cordless telecommunications system initially intended for wireless-public-branch-exchange applications, but which may also be used in the consumer market. DECT supports voice and data communications

Digital signal (DS)
A hierarchy of digital signal speeds used to classify capacities of digital lines and trunks. The fundamental speed level is DS-0 (64 kb/s). A signal that represents information by a series of fixed, encoded, rectangular pulses, usually consisting of two possible voltage levels. Each voltage level indicates one of tow possible values or logic states, such as on or off, open or closed, true or false. See also Analogue Signal.

Digital Signal Processor (DSP)
A microprocessor that digitizes analog signals.

Digital subscriber line (DSL)
A generic name for a family of digital lines provided by local telephone companies to their subscribers.

Digital transmission
A technique in which all information is converted into binary digits for transmission (string of discrete "on-off" or "high-low" pulses).

Digital video
Video signals represented by discrete numerical values rather than by continuously varying signal levels as in analog video. Because of this, it is simpler to maintain the fidelity of the video information as it travels through a transmission medium.

Digitize
The conversion of an analog or continuous signal into a data stream of binary digits.

Diluent
An ingredient usually added to an adhesive to reduce the concentration of bonding materials.

Dilute solution
A solution in which the sum of the volumes of the domains occupied by the solute molecules or particles is substantially less than the total volume of the solution. (IUPAC)

Dimer
Two monomers linked together. A polymer containing two monomers.

DIN
DIN connector is an electrical connector that was originally standardized in the early 1970s by the Deutsches Institut für Normung (DIN), the German national standards organization. … Some DIN connector standards are: DIN 41524, for circular connectors often used for audio signals.

DIN 7/16
Coaxial connector interface with screw type coupling mechanism. Larger than N interface and suitable for medium to high power applications. Frequency range is DC - 7.5 GHz.

Diode
An electronic device that restricts current flow chiefly to one direction. 

Diode adapter receptacle
Designed to house LED or PIN/APD diodes in a receptacle that allows the mating plug to position the fiber for an optimum coupling efficiency.

Dip Coating
An insulating coating applied to the conductor by passing the conductor through an applicator containing liquid insulating medium.

Dip Solder Terminal
The terminals on a connector which are inserted into holes in a PC board and then soldered into position.

Diplexer
A component used to provide two functions, such as multiplexing or filtering optical signals. For example, a diplexer used at an FTTx optical network terminal filters the downstream 1490-nm wavelength and multiplexes the upstream 1310-nm wavelength to or from a single fiber.

Dipole Antenna
Antenna with the gain, pattern and impedance defined at and near resonance of one-half wavelength. This antenna is split at its electrical center for connection to a transmission line. The radiation pattern is maximum at right angles to the axis of the antenna.

Direct Burial Cable
A cable installed directly in the earth.

Direct Buried
See buried.

Direct Capacitance
The capacitance measured directly from conductor to conductor through a single insulating layer.

Direct Current (DC)
An electric current that flows in only one direction, substantially constant in value.

Direct Current Resistance (DCR)
The resistance offered by any circuit to the flow of direct current.

Direction of Lay
The lateral direction in which the strands of a conductor run over the top of the cable conductor as they recede from an observer looking along the axis of the conductor or cable. Also applies to twisted cable.

Directional Antenna
An antenna which transmits or receives in certain directions more effectively than others.

Directional Coupler
A fiber optic coupler that preferentially transmits light in one direction.

Directionality
A quantification of how much light is passing in any direction, measured in dB. If a 0 dBm signal passes through a coupler with 50 dB directionality, only –50 dB (0.01 ?m) will pass in the wrong direction.

Directly-modulated laser (DML)
A laser directly modulated by electrical voltage and current.

Disconnect
A reusable conductive device designed to be separated from its mated part.

Discontinuity
1) A broken connection or the loss of a specific connection characteristic.  2) The temporary interruption or variation in current or voltage.

Discrete Wiring
Wire or wires having distinct identity and purpose.

Discruptive Discharge
A sudden, large increase in current through an insulation medium due to the complete failure of the medium under the electrostatic stress.

Dispersion
In fiber optics, the variation of the refractive index of a material with wavelength, causing light of different wavelengths to travel at different velocities in the material.

Dispersion compensation module (DCM)
Dispersion compensation modules use a chirped fiber Bragg gratings (FBG) and a optical circulator, which act as an individual wavelength or channel filter. Faster wavelengths are reflected further in the filter than slower wavelengths, enabling the slower wavelengths to catch up to the faster ones. The amount of delay is determined by the physical characteristics of the FBG. DCMs typically have insertion losses around 5 dB, consisting only of circulator and reflection losses. Tunable versions are also available.

Dispersion-compensating fiber (DCF)
A type of specialized fiber designed to offset or compensate for chromatic dispersion in single-mode fibers.

Dispersion-shifted fiber (DSF)
Specified by ITU-T G.653, this fiber provides low attenuation and dispersion at 1550 nm. It could not be used with DWDM as it caused four wave mixing, and has been obsoleted and replaced by G.655 nonzero dispersion-shifted (NZDS) fiber.

Disruptive Discharge
A sudden, large increase in current through an insulation medium due to the complete failure of the medium under the electrostatic stress.

Dissipation
Unusable or lost energy, such as the production of unused heat in a circuit.

Dissipation Factor
The tangent of the loss angle of the insulating material. (Also referred to as loss tangent, tand and approximate power factor.)

Dissipation Factor (Loss Tangent)
A measure of the loss characteristics of a dielectric material

Distortion
An unwanted change or addition to a signal or waveform when it is amplified. This definition excludes noise which is an extraneous signal superimposed on the desired signal.

Distributed feedback (DFB) laser
A laser that uses an internal grating to reduce the line width of the laser, and may be used for analog applications, e.g., AM/FM/DWDM.

Distributed Processing
A system or network whereby the processing is done at each individual workstation and not at a central device. A LAN is an example of distributed processing.

Distribution Cable
In telecommunications and CATV systems, the transmission cable between the distribution amplifier and the drop wire . A tight-buffered non breakout style cable mostly used for indoor installations. Jackets can be plenum, riser, or low smoke zero halogen to meet building codes. Internally, the fibers have a 900-micron coating. In the outside plant, the term “distribution cable” is used by service providers to describe the cable between the feeder (backbone) and drop cables.

Distribution Frame
A structure with terminations for connecting the permanent cabling of a facility in such a manner that interconnection or cross-connections may be readily made.

Distribution Panel
A combination of a patch panel and splice panel.

Distributor
The term used for the functions of a collection of components (for example, patch panels, patch cords) used to connect cables.

Disturbed Conductor
A conductor that receives energy generated by the field of another conductor or an external source such as a transformer.

Doctor Bar
Device that controls the amount of adhesive applied.

Doctor Blade
A scraper mechanism that regulates the dimensional thickness of adhesive on the spreader rolls or on the surface being coated. (Synonyms: doctor knife; doctor bar.)

Doctor Roll
A revolving roller mechanism resulting in a wiping action for regulating the adhesive supplied to the spreader roll.

Dog-Leg
Permanent short bend or kink in a wire rope caused by improper use

Domain
An area including all peripherals and nodes under control of a single computer or server in a network.

Domains
sequences or regions in block copolymers.

Domestic Wire Rope
Wire rope that is stranded and closed in the United States of America

Domstat
Domestic communications satellite

Dopant
A material, usually germanium or boron oxide, added to silica to change its index of refraction.

Doping
Controlled addition of small quantities of an impurity to a pure substance in order to change its characteristics, e.g., increase the refractive index of the fiber core.

DOS
Disk Operating System

Dot Coding
Process of tool imprinting a 22-10 AWG PIDG terminal. Sot coding indicates whether the proper tool has been used.

Double Bond
Two covalent bonds (two shared pairs of electrons between two atoms) represented by "=" (Examples: C=C, C=O)

Double Crimp
The process of tow or more mechanical crimping operations on the same location in a single terminal.

Double Shield
Two shields, on over the other, used to improve the shield effectiveness.

Double spread adhesive
An application of adhesive to both adherends or as two layers on one adherend.

Double-strand chain
Ladder chain a chain that comprises constitutional units always joined to each other through four atoms, two on each constitutional unit. (IUPAC)

Double-strand copolymer
Ladder copolymer a copolymer, the macromolecules of which are double-strand chains. (IUPAC)

Double-strand polymer
Ladder polymer a polymer, the macromolecules of which are double-strand chains. (IUPAC)

Dowel
A cylindrical pin used to reinforce the strength of an assembly joint.

Downline Impedance
LAN Cable Testers perform this function using a Time Domain Reflectometer (TDR) that samples and analyzes the impedance of a link. Relative Impedance is measured as a function of length and each cable can be viewed in graphical format along its length to ascertain where the anomalies are located, whereas Characteristic Impedance is usually measured in a laboratory with complex test equipment such as an expensive network analyzer. The TDR measures relative impedance in the field to find crimps, kinks and/or stretched cable that would show up as a blips, peaks or valleys on the otherwise flat line graph of a good link. (also see FAULT FIND)

Downlink
The transmission of RF signals from a satellite to an earth station.

Drain Wire
In a cable, an insulated wire laid over the component or components, usually under aluminized Mylar and used for a ground connection.

Draw
A step during the optical fiber manufacturing process in which a consolidated preform is loaded into a high temperature furnace and “drawn down” to the diameter of an optical fiber’s cladding, then cooled.

Draw Feed Stock
Rod or wire that is subsequently drawn to a smaller size.

Drawing
In the manufacturing of wire, pulling the metal through a die or series of dies for reduction of diameter to a specified size.

Driver IC
An amplifier in an integrated circuit that increases signal current to the LED for greater transmission distance.

Drop Cable
A cable connecting a workstation or peripheral to the main network cable.

Drop Ceiling
A ceiling that creates an area or space between the ceiling material and the structure above the material. Synonym: False Ceiling, Suspended Ceiling.

Drop Ship
A process where customers buy the parts and materials and they are shipped to the manufacturer. The manufacturer then builds the products and deliver completed assemblies or cables to the customer. 

Drop Wire
A telephone cable, usually consisting of one insulated telephone pair, which is used to connect a subscribers premises to open wire lines on poles.

Drum
A cylindrical flanged barrel of uniform or tapering diameter on which rope is wound for operation or storage. It may be smooth or grooved

Dry
To change the physical state of an adhesive or a substrate by the loss of solvent constituents by evaporation or absorption, or both.

Dry bond adhesive
Synonym for contact adhesive.

Dry fit
It is when fiber is inserted into a plug’s ferrule or termini to verify the strip length and fit prior to insertion of the bonding adhesive. This helps the technician to recognize the “feel” of the fiber insertion process.

Dry Strength
The strength of an adhesive joint determined immediately after drying under specified conditions or after a period of conditioning in a standard laboratory atmosphere.

Drying agent
A component of a sealant that accelerates the oxidation of oils or unsaturated polymers.

Drying temperature
The temperature to which an adhesive or an assembly is subjected to dry the adhesive.

Drying time
1) The period of time during which an adhesive or an assembly is allowed to dry, with or without the application of heat or pressure, or both; 2) The interval of time between the point of liquid adhesive application to the adherend substrate and the time at which adhesive particle coalescence occurs.

Dual Coaxial Cable
Two individually insulated conductors laid parallel or twisted and placed within an overall shield and sheath.

Dual in-line package (DIP)
Only refers to pigtailed dual in-line packaged devices.

Dual MTJ Testing
Using two MTJs, one at either end of DUT, not necessarily Bir-Directional.

Dual Self-Normal Jack
A jack that provides a connection between the two rear connectors, except when interrupted by the insertion of a video patch plug in either of the two front panel receptacles.

Dual-Fiber Cable
A type of fiber optic cable that has two single-fiber cables enclosed in a jacket of extruded plastic.

Dual-Mode Phone
A phone that operates on analog and digital networks.

Dubbing
Electronic duplicating of recorded audio and/or video signals.

Duct
(1) A single enclosed raceway for wires or cables. Also Conduit, Raceway; (2) a single enclosed raceway for wires or cables usually used in soil or concrete, (3) an enclosure in which air is moved. Generally part of the HVAC system of a building.

Ductile
Capable of being drawn out or hammered thin, or of being flexed or bent without failure.

Ducts
The main feeder channels in which communication cable is routed between buildings in a campus environment. See also Campus Backbone Cable.

DUKPT
Derived Unique Key Per Transaction

Dummy Connector Assembly electrical
Two or more electrical connectors having common mounting or mounted on each other, each one capable of being independently replaced. Excludes items which are furnished as mated pairs or sets. (MIL-STD)

Dummy Connector Plug
A connector device designed to mate with a receptacle connector to perform protective, environmental and/or electrical shorting functions.

Dummy Connector Receptacle
A connector receptacle which does not have provisions for attaching conductors. It is generally used for storage of a cable assembly connector plugs. (MIL-STD)

Dummy Load
A dissipative device used at the end of a transmission line or waveguide to convert transmitted energy into heat, so essentially no energy is radiated outward or reflected back to its source.

Duplex
Referring to a type of data transmission, either half or full. Half duplex permits only one-way communication. Full duplex allows simultaneous two-way transmission.

Duplex Cable
(1) A cable composed of two insulated single conductor cables twisted together. (2) A cable composed of two fibers typically 62.5/125 mm Multi-Mode, placed in parallel under a thermoplastic sheath.

Duplex Parallel
Typically used in the thermocouple industry to denote two parallel conductors of dissimilar metals insulated in parallel without twist and jacketed. Commonly applied to thermocouple grades and extension wires

Duplex Transmission
1) Data transmission over a circuit capable of transmitting in both directions at the same time.  2) Synonymous with full duplex transmission.

Durability
As related to adhesive joints, the endurance of joint strength relative to the required service conditions.

Durometer
A measurement used to denote the hardness of a substance, usually an elastomer.

Dust Cap
A protective cover that fits tightly over the connector ferrule, plug, or sleeve. Usually made of plastic, it is used to keep the connector endface clean.

Dust Cover
An item which is specifically designed to cover the mating end of a connector for mechanical and/or environmental protection. (MIL-STD)

DUT
Device Under Test.

DVB Project
Digital Video Broadcasting Project

DWDM
See DENSE WAVELENGTH DIVISION MULTIPLEXING.

Dwell cycle
The period of time after a panel has been cured in radio frequency, but before pressure is released to allow additional cure and equalizing.

Dynamic range
For an optical instrument, defined (in dB) as the ratio of the smallest signal that can be observed at a specified wavelength separation in the presence of a strong nearly-saturating signal.
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