Electronics (Mike Jaroch)
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D'ARSONVAL METER MOVEMENTThe permanent-magnet moving-coil movement used in most meters [3] [16]. | ||
DAMPED WAVEA sinusoidal wave in which the amplitude steadily decreases with time. Often associated with energy loss [9]. | ||
DATA PROCESSINGThe execution of a systematic sequence of operations performed upon data. Synonymous with information processing [13]. | ||
DATA TRANSMISSIONThe transfer of information from one place to another or from one part of a system to another [15]. | ||
dBmAn abbreviation used to represent power levels above or below a 1-milliwatt reference [16]. | ||
DEAD SHORTA short circuit having minimum resistance [1]. | ||
DECIMALPertaining to the number representation system with a radix of ten [13]. | ||
DECIMAL DIGITIn decimal notation, one of the characters 0 through 9 [13]. | ||
DECIMAL NOTATIONA fixed radix notation where the radix is ten [13]. | ||
DECIMAL NUMERALA decimal representation of a number [13]. | ||
DECIMAL POINTThe radix point in decimal representation [13]. | ||
DECOUPLING CAPACITORA capacitor used to transfer unwanted signals out of a circuit; for example, coupling an unwanted signal to ground. Also called a BYPASS CAPACITOR [8]. | ||
DEFLECTION COILSIn a cathode-ray tube, coils used to bend an electron beam a desired amount [18]. | ||
DEFLECTION PLATESTwo pairs of parallel electrodes, one pair set forward of the other and at right angles to each other, parallel to the axis of the electron stream within an electrostatic cathode-ray tube [6]. | ||
DEGENERATIONThe process whereby a part of the output signal of an amplifying device is returned to its input circuit in such a manner that it tends to cancel part of the input [7]. | ||
DEGENERATIVE FEEDBACKFeedback in which the feedback signal is out of phase with the input signal; also called NEGATIVE FEEDBACK [8]. | ||
DEGREE-OF-FREEDOMThe number of axes about which a gyro is free to precess [15]. | ||
DEIONIZATION POTENTIALThe potential at which ionization of the gas within a gas-filled tube ceases and conduction stops; also referred to as extinction potential [6]. | ||
DEIONIZATION TIMEIn a spark gap, the time required for ionized gas to return to its neutral state after the spark is removed [18]. | ||
DELTAA three-phase connection in which windings are connected end-to-end, forming a closed loop that resembles the Greek letter delta. A separate phase wire is then connected to each of the three junctions [5]. | ||
DEMODULATIONThe removal of intelligence from a transmission medium [12]. | ||
DEMODULATORA circuit used in servosystems to convert an ac signal to a dc signal. The magnitude of the dc output is determined by the magnitude of the ac input signal, and its polarity is determined by whether the ac input signal is in or out of phase with the ac reference voltage [15]. | ||
DeMORGAN'S THEOREMA theorem which states that the inversion of a series of AND applications is equal to the same series of inverted OR applications, or the inversion of a series of OR applications is equal to the same series of inverted AND applications. | ||
DENSITY(1) The compactness of a substance. (2) Mass per unit volume [10]. | ||
DEPLETION REGIONThe region in a semiconductor where essentially all free electrons and holes have been swept out by the electrostatic field which exists there [7]. | ||
DEPOT-LEVEL MAINTENANCE (SM&R CODE D)Supports SM&R Code I and SM&R Code O activities through extensive shop facilities and equipment and highly skilled personnel [14]. | ||
DESIGNATIONOperational phase of a fire-control or track radar during which the radar is directed to the general direction of a desired target [18]. | ||
DETECTIONThe separation of low-frequency (audio) intelligence from the high-frequency carrier [17]. | ||
DETECTORA mixer or converter in a superheterodyne receiver [18]. | ||
DICEUncased chips [14]. | ||
DIE BONDINGProcess of mounting a chip to a package [14]. | ||
DIELECTRICAn insulator; a term applied to the insulating material between the plates of a capacitor [2]. | ||
DIELECTRIC CONSTANTThe ratio of a given dielectric to the dielectric value of air [2] [11]. | ||
DIELECTRIC FIELDThe space between and around charged bodies in which their influence is felt. Also called ELECTRIC FIELD OF FORCE or an ELECTROSTATIC FIELD [1]. | ||
DIELECTRIC HEATINGThe heating of an insulating material by a high-frequency electric field [10]. | ||
DIELECTRIC HYSTERESIS LOSSPower loss of a capacitor because of the changes in orientation of electron orbits in the dielectric; the changes in orientation are caused by rapid reversal in polarity of line voltage. The higher the frequency, the greater the loss [2]. | ||
DIELECTRIC LEAKAGEPower loss of a capacitor because of the leakage of current through the dielectric. Also relates to leakage resistance; the higher the leakage resistance, the lower the dielectric leakage [2]. | ||
DIELECTRIC LOSSESThe losses resulting from the heating effect on the dielectric material between conductors [10] [11]. | ||
DIELECTRIC STRENGTHThe ability of an insulator to withstand a potential difference without breaking down (usually expressed in terms of voltage) [4]. | ||
DIFFERENCE FREQUENCYSee BEAT FREQUENCY [18]. | ||
DIFFERENCE OF POTENTIALA voltage between two points [6]. | ||
DIFFERENTIAL AMPLIFIERA circuit that amplifies the difference between two input signals [8]. | ||
DIFFRACTIONThe bending of waves (as light or RF) when the waves are met with some form of obstruction [10]. | ||
DIFFUSION(1) The scattering of reflected light waves from an object, such as white paper [10]. (2) Controlled application of impurity atoms to a semiconductor substrate [14]. | ||
DIGITA symbol that represents one of the nonnegative integers smaller than the radix. For example, in decimal notation a digit is one of the characters from 0 through 9 [13]. | ||
DIGITAL COMPUTER(1) A computer in which discrete representation of data is used. (2) A computer that operates on discrete data by performing arithmetic and logic processes on these data [13]. | ||
DIODEAn electron tube containing two electrodes: a cathode and a plate [6]. (2) A two element, solid-state device made of either germanium or silicon; it is primarily used as a switching device [7] [13]. | ||
DIODE DETECTORA demodulator that uses one or more diodes to provide a rectified output with an average value that is proportional to the original modulation [12] [18]. | ||
DIPOLEA common type of half-wave antenna made from a straight piece of wire cut in half. Each half operates at a quarter wavelength of the output [10]. | ||
DIRECT CURRENTAn electric current that flows in one direction only [1]. | ||
DIRECT SHORTSame as SHORT CIRCUIT [3]. | ||
DIRECTIONAL ANTENNAAn antenna that radiates most effectively in only one direction [18]. | ||
DIRECTIONAL COUPLERA device that samples the energy traveling in a waveguide in one direction only [11]. | ||
DIRECTIVITYThe ability of an antenna to radiate or receive more energy in some directions than in others. The degree of sharpness of the antenna beam [10] [11] [18]. | ||
DIRECTLY HEATED CATHODEA wire, or filament, designed to emit the electrons that flow from cathode to plate. The filament is designed so that a current is passed through it; the current heats the filament to the point where electrons are emitted [6]. | ||
DIRECTORThe parasitic element of an array that reinforces energy coming from the driver element [10]. | ||
DISCRETE COMPONENTSIndividual transistors, diodes, resistors, capacitors, and inductors [14]. | ||
DISCRIMINATORA circuit in which amplitude variations are derived in response to phase or frequency variations [18]. | ||
DISPERSIONThe refraction of light waves that causes the different frequencies to bend at slightly different angles [10]. | ||
DISPLACEMENT CURRENTThe current that appears to flow through a capacitor [2]. | ||
DISTILLED WATERWater that has been purified through a process of evaporation and condensation [18]. | ||
DISTORTIONAny unwanted change between an input signal and output signal [6] [8]. | ||
DISTRIBUTED CONSTANTSThe constants of inductance, capacitance, and resistance in a transmission line. They are spread along the entire length of the line and cannot be distinguished separately [10]. | ||
DISTRIBUTIVE LAWIn Boolean algebra the law which states that if a group of terms connected by like operators contains the same variable, the variable may be removed from the terms and associated with them by the appropriate sign of operation (for example, A(B + C) = AB + AC) [13]. | ||
DOMAIN THEORYA theory of magnetism based upon the electron-spin principle. Spinning electrons have a magnetic field. If more electrons spin in one direction than another, the atom is magnetized [1]. | ||
DOMINANT MODEThe easiest mode to produce in a waveguide, and the most efficient mode in terms of energy transfer [11]. | ||
DONORAn impurity that can make a semiconductor material an N-type by donating extra "free" electrons to the conduction band [7]. | ||
DONOR IMPURITYSee PENTAVALENT IMPURITY [7]. | ||
DOORKNOB TUBEAn electron tube that is similar to the acorn tube but larger. The doorknob tube is designed to operate, at high power, in the uhf frequencies [6]. | ||
DOPINGThe process of adding impurities to semiconductor crystals to increase the number of free charges that can be moved by an external, applied voltage. Doping produces N-type or P-type material [7] [14]. | ||
DOPPLER EFFECT(1) The apparent change in frequency or pitch when a sound source moves either toward or away from a listener [10]. (2) In radar, the change in frequency of a received signal caused by the relative motion between the radar and the target [18]. | ||
DOPPLER FREQUENCYThe difference between transmitted and reflected frequencies; caused by the Doppler effect [18]. | ||
DOUBLE NEGATIVE LAWIn Boolean algebra, the law which states that the complement of a complement is the equivalent of the original term [13]. | ||
DOUBLE RECEIVERA fine and coarse synchro receiver enclosed in a common housing with a two- shaft output (one shaft inside the other) [15]. | ||
DOUBLE-MODINGIn a transmitter output tube, the abrupt and random change from one frequency to another [18]. | ||
DOUBLETAnother name for the dipole antenna [10]. | ||
DOUBLING UPThis is a type of two-equipment installation where one unit can be substituted for another in the event of failure [17]. | ||
DOWN LINKThe frequency used to transmit an amplified signal from a satellite or other craft back to earth [17]. | ||
DRIFT SPACEIn an electron, a region free of external fields in which relative electron position depends on velocity [11]. | ||
DRIVEN ARRAYAn array in which all of the elements are driven [10]. | ||
DRIVEN ELEMENTThe element of an antenna connected directly to the transmission line [10]. | ||
DRIVERThe final stage of amplification [8]. | ||
DRUM-TYPE ARMATUREAn efficient, popular type of armature designed so that the entire length of the winding is cutting the field at all times. Most wound armatures are of this type [5]. | ||
DRY CELLAn electrical cell in which the electrolyte is not a liquid. In most dry cells the electrolyte is in the form of a paste [1]. | ||
DRY-AIR SYSTEMProvides dehumidified air for electronic equipment that is moisture critical [18]. | ||
DUAL IN-LINE PACKAGE (DIP)IC package having two parallel rows of preformed leads [14]. | ||
DUAL-GATE MOSFETA two-gate MOSFET in which either gate can control the conductor independently, a fact which makes this MOSFET very versatile [7]. | ||
DUCTILEEasily drawn out (as to form filaments or wires) [4]. | ||
DUCTINGTrapping of an RF wave between two layers of the earth's atmosphere or between an atmospheric layer and the earth [18]. | ||
DUMMY ANTENNASee DUMMY LOAD [16]. | ||
DUMMY LOADA dissipative but nonradiating device that has the impedance characteristics of an antenna or transmission line. Also called ARTIFICIAL LOAD [11] [16] [17]. | ||
DUPLEXERA radar device that switches the antenna from the transmitter to the receiver and vice versa [18]. | ||
DUTY CYCLEIn a transmitter, ratio of time on to time off [12] [18]. | ||
DYNAMIC MICROPHONEA device in which sound waves move a coil of fine wire that is mounted on the back of a diaphragm and located in the magnetic field of a permanent magnet [12]. | ||