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fices resolution at greater ranges. longitudinal wave
log taper In a potentiometer or rheostat, resistance
variations that correspond to the logarithm of
shaft rotation, or vice versa. Compare LINEAR long line 1. A single-wire antenna whose length is
TAPER. Also see TAPER. greater than the length of the wave fed to it for
long Abbreviation of LONGITUDE. propagation. Also see LONG-WIRE ANTENNA.
long-distance communication 1. Radio commu- 2. In wire telegraphy, an electrical line that has
nication between stations separated by distances great physical length. 3. In electronics theory, a
too great for ground-wave propagation to be effec- transmission line of indeterminate length, but
tive. 2. In telephone service, communications whose characteristics remain stable and pre-
that require the dialing of an area code in addi- dictable to infinity.
tion to the local exchange number. long-persistence screen A cathode-ray-tube
long-distance loop A direct telephone line con- screen on which the image remains for a time af-
necting a subscriber™s station to a long distance ter the electron beam has passed.
switchboard. long-play Abbreviation, LP. Descriptive of phono-
long-distance reception Reception of radio sig- graph discs designed to play at 33.3 revolutions
nals from stations beyond the range of ground- per minute (rpm). Also see MICROGROOVE
wave propagation. See also LONG-DISTANCE RECORD.
long-distance transmission Transmission of ra- long-range navigation See LORAN.
dio signals to points beyond the range of ground- long-range radar Radar that can detect targets at
wave propagation. See also LONG-DISTANCE distances of 200 miles or more.
COMMUNICATION, 1. long skip Ionospheric radio-wave propagation,
longitude Abbreviation, long. Angular displace- usually via the F layer, between or among sta-
ment, measured in degrees around the earth™s tions separated by large geographic distances.
circumference, to the east and west of the prime The wave angles of departure (from transmitting
meridian that passes through Greenwich, En- stations) and arrival (at receiving stations) are
gland. Compare LATITUDE. Also see MERIDIAN. very small relative to the horizon. Compare
longitude effect The variation (caused by the SHORT SKIP.
earth™s rotation and magnetic field) of the long-term drift Gradual change in the value of a
strength of cosmic rays arriving at different longi- quantity, such as voltage or frequency, observed
tudes on the surface of the earth. over a long period, in contrast to that noted for a
longitudinal current Current flowing in the same brief interval. Compare SHORT-TERM DRIFT.
direction in the parallel wires of a pair (the return long-term input offset voltage stability Ex-
circuit is via ground). pressed in microvolts per month. The extent to
long-term input offset voltage stability • Lorentz force

which the input offset voltage in an integrated cir-
cuit stays stable over long periods of time.
long-term stability Stability reckoned over a pe-
riod of weeks, months or years, as contrasted to
that noted for brief intervals of time (minutes or
long throw A speaker design term that describes a
woofer moving through long excursions; the ob-
jective is to provide good low-frequency response
with low distortion.
long waves Low-frequency radio waves, particu-
larly those in the frequency range of 30 kHz to
300 kHz (10 km to 1 km).
long-wire antenna A horizontal or sloping wire an- looping plug
tenna measuring a full wavelength or more and
fed at a high-current point or at one end. As the
wire is made longer, the main radiation/response loop-input signal A signal introduced into a feed-
lobes get more nearly in line with the antenna, back control loop.
and their amplitudes increase. As the wire is loop pulsing The regular, intermittent breaking of
made shorter, the main lobes get farther from the the direct-current path at the transmitting end of
axis of the antenna, and their amplitudes de- a transmission line; also called DIAL PULSING.
crease. This antenna can produce high gain and loop resistance The resistance of the electrical
excellent low-angle radiation, provided it is path around a complete loop (see LOOP, 1).
straight, is at least several wavelengths long, and loop response time In a security system, the
is clear of obstructions. However, it cannot be ro- length of time between the first sensing of an ab-
tated conveniently to change the direction in normal condition (e.g., an intrusion) and the
which maximum gain occurs. Also, a great deal of recognition of that condition by the controller.
real estate is needed at medium and high fre- loopstick antenna See FERRITE-ROD ANTENNA.
quencies. loop test A means of locating a discontinuity in a
lookup A computer programming technique in circuit by creating a closed loop, including the
which a data item identified by a key is selected suspected fault point.
from an array. loose coupling Coupling that transfers only small
loop 1. An electrical circuit consisting of elements amounts of energy, as when a primary and sec-
connected in series. 2. In a standing-wave sys- ondary coil are spaced so far apart that the coef-
tem, a maximum-response point (e.g., current ficient of coupling is small. Compare CLOSE
loop and voltage loop). Compare NODE, 2. 3. See COUPLING.
LOOP ANTENNA. 4. A signal path (e.g., feed- loosely coupled twin In computer operations, a
back loop). 5. A one- or two-turn coil for low- system in which two processors, each having its
impedance coupling. Also see LINK, 1. 6. In a own operating system, are used with switches so
computer program run, the repetitious execution that they can use common peripherals. Also see
of a series of instructions that terminates when SWITCH.
some specified condition is satisfied by a rela- lopplar Acronym for laser Doppler radar. Also ab-
tional test, at which point the next instruction in breviated as ladar.
the main program is obeyed. lorac A radio-navigation system that operates by
loop antenna 1. A small portable receiving an- means of phase comparison. Similar to LORAN.
tenna in the form of a wire coil. 2. A half-wave Trade name of Seismograph Service Corporation.
conductor bent into a circle or square. The con- loran A long-range radionavigation system in
ductor is broken at the point opposite the feed which two pairs of ground stations transmit
point. It can be used for transmitting and receiv- pulsed signals that are used by aircraft and ships
ing. 3. A full-wavelength, continuous conductor to determine their positions. The name is an
bent into a circle or square. It can be used for acronym for long-range navigation.
transmitting and receiving. loran C A radionavigation system that operates at
loop checking A method of checking the accuracy a frequency of 100 kHz. It operates on the hyper-
of data transmitted over a data link by returning bolic principle.
signals received at one terminal to the transmit- loran D A radionavigation system similar to loran
ting terminal for comparison with the original C. It is used by aircraft, operates independent of
data. ground stations, and prevents unwanted enemy
looped amplification See FEEDBACK FACTOR. detection of aircraft position.
looping plug A double phone-plug unit for simul- Lorentz force For a charge Q moving with velocity
taneously plugging into two phone jacks. Com- v in a magnetic field B and an electric field E, the
force F = Q(E + (v — B)).
pletes (loops) the circuit between the two jacks.
420 loss • lower sideband suppressed carrier

loss Energy that is dissipated without doing useful tions, those radio channels between 30 MHz
work in a circuit or system. See POWER LOSS. and about 70 MHz.
loss angle For an insulating material, 90 degrees low battery 1. The condition of a battery needing
minus the PHASE ANGLE. replacement or recharging. 2. An indicating de-
loss index For an insulating material, the product vice that shows when a battery needs to be re-
of the POWER FACTOR and the DIELECTRIC placed or recharged.
CONSTANT. low-battery bias current The current into a desig-
lossless data compression A process in which nated pin of an integrated circuit required for
the number of bits in a data file is reduced by proper operation of the LOW-BATTERY INDICA-
eliminating redundancies, without sacrificing TOR.
any of the precision or detail in the file. Com- low-battery indicator A device, such as a light-
pression of text and programs must usually be emitting diode (LED) and associated circuitry,
lossless. Image compression need not generally that gives a visible indication of the condition of
SION. low-capacitance probe A test probe in which ca-
lossless line A perfect transmission line (i.e., one pacitance has been minimized to reduce loading
having no resistance loss, no dielectric loss, and and detuning of the circuit under test.
no radiation loss). It is not realizable in practice, low earth orbit Acronym, LEO. An artificial satellite
but useful in some theoretical calculations. orbit that is comparatively low in altitude, resulting
loss tangent See DISSIPATION FACTOR, 1. in a short orbital period (in some cases less than 2
lossy data compression A process in which the hours). See also LEO SATELLITE SYSTEM.
number of bits in a data file (especially a digital low-energy criterion See VON HIPPEL BREAK-
image) is reduced by eliminating redundancies, DOWN THEORY.
with some sacrifice of precision or detail. In image lower sideband Abbreviation, LSB. In an ampli-
compression, some loss can usually be tolerated, tude-modulated wave, the lower band of frequen-
allowing larger compression ratios than would be cies equal to the difference between the carrier
possible if zero loss were mandatory. Lossy com- frequency and the modulating frequency. Com-
pression is not generally acceptable for text files pare UPPER SIDEBAND.
and programs. Compare LOSSLESS DATA COM- lower sideband suppressed carrier Abbreviation,
PRESSION. LSSC. A single-sideband transmission technique
lossy line A line or cable having comparatively in which the lower sideband is transmitted,
high or excessive attenuation per unit length. but the upper sideband and carrier are sup-
loudness The amplitude of sound, especially in au- pressed. Compare DOUBLE SIDEBAND SUP-
dio reproduction equipment, such as a high- PRESSED CARRIER and UPPER SIDEBAND
fidelity stereo amplifier. Also called VOLUME. SUPPRESSED CARRIER.
loudness control See COMPENSATED VOLUME
loudness curves See AUDIBILITY CURVES.
loudness switch/button In a high-fidelity audio
amplifier, a switch or button that can be actuated
when music is played at low loudness. Increases
the volume of the bass relative to the midrange
and treble.
loudspeaker A transducer that converts electrical
impulses into sound waves of sufficient volume to
be heard easily by a number of listeners situated
at some distance from the device. Also called
loudspeaker damping See DAMPED LOUD-
loudspeaker dividing network See CROSSOVER
low 1. The logical digit 0. 2. Of relatively small
magnitude (e.g., LOW VOLTAGE and LOW-
FREQUENCY). 3. In a rechargeable cell or battery,
the condition of being near the end of the dis-
charge cycle.
low band 1. The low or lowest frequency band
used in communications, testing, or processing
in a given situation. 2. Television channels 2 to
6 (54 to 88 MHz). 3. In two-way radio opera-
lowest usable frequency • low power

lowest usable frequency Abbreviation, LUF. The low-level output current 1. A test to ascertain
lowest frequency that can be used successfully at that the fan-out and current-sinking capability of
a given time for communication via the iono- an integrated circuit are as specified. 2. The cur-
sphere. Compare MAXIMUM USABLE FRE- rent flowing into an output with input conditions
QUENCY. that cause the output to be at logic low.
low filter A highpass filter that removes low- low-level signal 1. A signal with small amplitude.
frequency audio noise from the modulating wave- 2. A signal with peak-to-peak voltage so low that
form of a broadcast station. The result is a lower it does not drive an amplifier circuit out of the lin-
level of transmitted hum and rumble. ear range of operation.
low-frequency Abbreviation, LF. 1. Pertaining to low-loss material A material, particularly a dielec-
radio frequencies in the band from 30 kHz to 300 tric, having low electrical loss at a given fre-
kHz (wavelengths from 10 kilometers to 1 kilome- quency. Also see LOSS.
ter). Also see RADIO SPECTRUM. 2. Pertaining to low-noise Pertaining to circuits, especially weak-
audio frequencies below 500 Hz. signal communications receiving amplifiers and
low-frequency compensation 1. In video- converters, designed to generate the smallest
amplifier design, special measures, such as use possible amount of internal noise.
of high coupling and bypass capacitances, to low-noise down converter In a satellite television
boost low-frequency gain. 2. Use of special circuits receiving system, a circuit that converts the sig-
to increase the low-frequency response of an audio nals from the dish antenna to frequencies that
amplifier. Also see BASS BOOST, 1, 2. correspond to the channels on a conventional
low-frequency direction finder Abbreviation, television set.
LDF. A direction finder operated in or below the low order The lesser-value place(s) of characters or
standard amplitude-modulation (AM) broadcast digits in the hierarchy of a group (number or
band, that is, below 1.605 MHz. word). For example, 5 and 6 are low-order digits
low-frequency padder See OSCILLATOR PAD- in the number 123,456.
DER. low-order position The extreme right-hand (least
low-frequency parasitics Parasitic oscillations of significant) position in a number or word.
a frequency lower than that being processed by low-pass filter A combination of capacitance, in-
the amplifier or generated by the oscillator in ductance, and/or resistance, intended to produce
which they occur. large amounts of attenuation above a certain fre-
low-level 1. A logic term for the more negative of quency and little or no attenuation below that fre-
the two (binary) logic levels. 2. Having an ampli- quency. The frequency at which the transition
tude that is below that normally available in com- occurs is called cutoff. At cutoff, the power atten-
parable circuits or systems. 3. In computer uation is 3 dB with respect to the minimum at-
operations, pertaining to programming languages tenuation. At frequencies below cutoff, the power
(such as assembly language or machine lan- attenuation is less than 3 dB. At frequencies
guage) that control the machine, but do not di- above cutoff, the power attenuation is more than
rectly interface with the operator. 3 dB. The simplest circuit consists of a series in-
low-level audio signal In audio operations, a sig- ductor or a parallel capacitor. The inductance-
nal that has not been amplified by any means capacitance (LC) circuit has a combination of
(e.g., the output of a dynamic microphone). Com- series inductors and parallel capacitors. In the
pare HIGH-LEVEL AUDIO SIGNAL. resistance-capacitance (RC) circuit, resistors are
low-level contact A switch or relay contact intended substituted for the inductors. Compare BAND-
for use with low values of current and voltage. PASS FILTER, BAND-REJECTION FILTER,
low-level input current 1. A test used to check an HIGH-PASS FILTER.
input pull-up resistor in an integrated circuit to low power Abbreviation, LP. Power considerably
ensure that the fan-in is as specified. 2. The cur- lower than that ordinarily encountered in a
rent flowing from an input when the highest low-
level output voltage specified is applied to the
input of the device. L L
low-level language A computer programming lan-
guage in which each instruction has only one
equivalent machine code. Examples are machine
In Out
language and assembly language. Compare
low-level logic Abbreviation, LLL. In digital-
computer operations, any logic system that
operates at low voltage or current levels.
low-level modulation Modulation of a radio or
television transmitter at a stage preceding the fi-
low-pass filter
nal radio-frequency (RF) power amplifier.
422 low power • lug

particular application. The term is arbitrary; sev- capital letter L. 2. An attenuator circuit whose
eral hundred watts might be regarded as low schematic representation has the general shape
power in one situation, whereas a fraction of a of an inverted capital letter L. 3. A network sec-
watt would be implied in another. tion consisting of a series (input) impedance arm
low-print recording tape Magnetic tape that is and a shunt (output) impedance arm. See L PAD.
less susceptible to print-through than conven- 4. A right-angle bend in coaxial cable (see ELL).
low Q For a component or circuit, a low quotient for LSSC Abbreviation of LOWER SIDEBAND SUP-
the ratio of reactance to resistance (X/R). This is a PRESSED CARRIER.
relative term because a particular Q value consid- LT band A section of the L BAND extending from
ered low in one situation might be high in other 780 to 900 MHz.
circumstances. Also see FIGURE OF MERIT, 1. LTROM Abbreviation of LINEAR-TRANSFORMER
low voltage 1. A voltage considerably lower than L-type antenna See INVERTED-L ANTENNA.
that ordinarily encountered in a particular appli- L-type voltage regulator A simple voltage regula-
cation. The term is arbitrary; several hundred tor containing a series current-limiting resistor
volts might be regarded as low in one situation, and shunt regulator (zener diode, VR tube, volt-
and a fraction of a volt would be implied in an- age-dependent resistor, etc.). The schematic
other. 2. In a television receiver, the supply volt- representation resembles an inverted capital
age applied to all points other than the letter L.
high-voltage circuit or the picture tube.
low-voltage rectifier In a television receiver, the
Unreg Unreg
rectifier that supplies power for the low-voltage
+ + + +
stages. See LOW VOLTAGE, 2.
LP 1. Abbreviation of LOW POWER. 2. Abbreviation R1
Reg + (High)
of LONG PLAY. 3. Abbreviation of low pressure. R1
L pad An attenuator consisting of one series arm
From From
and one shunt arm, arranged in such a way that
power power VR
the schematic representation of the circuit re-
supply supply
sembles an inverted capital letter L. It is noted for
Reg + (Low)
output output
its constant input resistance or impedance as the
amount of attenuation is varied.
LP band A section of the L BAND extending from
390 to 465 MHz.
lpm Abbreviation of lines per minute: the output ’ ’ ’ ’
speed of a line printer.
lpW Abbreviation of lumens per watt; lm/W is pre-
ferred. L-type voltage regulator
Lr Symbol for LAWRENCIUM.
L + R, L “ R The sum and difference of the left (L)
and right (R) channel signals in a stereo high- lt-yr Abbreviation of LIGHT-YEAR.
fidelity sound system. The L + R signal is the in- Lu Symbol for LUTETIUM.
phase combination of the two channels; the L “ R Lucalox General Electric™s translucent ceramic; its
signal is the out-of-phase combination. chief constituent is polycrystalline alumina. The
L regulator See L-TYPE VOLTAGE REGULATOR. material has many applications in electro-optics.
LRR Abbreviation of LONG-RANGE RADAR. Lucite Trade name for METHYL METHACRYLATE
TANCE TIME CONSTANT. Luddites During the Industrial Revolution, people
LSA diode Abbreviation for limited-space-charge- who sabotaged automated factory equipment be-
accumulation diode. A solid-state diode that acts cause they believed the machines would put
as a microwave oscillator. them out of work. The word comes from the name
LSB 1. Abbreviation of LOWER SIDEBAND. 2. Ab- of Ned Ludd, their supposed leader. The term is
breviation of LEAST-SIGNIFICANT BIT. sometimes applied nowadays to people who fear
LS band A section of the L band that extends from computers, robots, and other technological inno-
900 to 950 MHz. vations because of real or imagined threats to
LSC Abbreviation of LEAST-SIGNIFICANT CHAR- personal job security.
L section 1. A filter section whose schematic rep- lug 1. A contact attached to the end of a wire lead
resentation has the general shape of an inverted to facilitate connection to a binding post. 2. A
lug • LZT

contact attached to a terminal strip, to which
rays Photoconductive
wire leads are soldered.
lum Abbreviation of LUMEN. The preferred (SI)
form is lm.
lumen Abbreviation, lm, and sometimes l or lum.
The SI unit of luminous flux; it is equal to the Signal
light that is emitted in one steradian (the unit output
solid angle) by a uniform point source of one can-
lumen-hour Abbreviation, lm-hr. The amount of Electroluminescent
light that a source having a luminous flux of one cell
LUMEN delivers in a time period of one hour.
luminaire A complete and self-contained lighting lumistor
system, for television-studio use or photographic
use. The kit includes all of the needed parts and ing distributed through a circuit (e.g., lumped ca-
accessories. pacitance and lumped inductance).
luminance The amount of light emitted or scat- lumped capacitor See DISCRETE CAPACITOR.
tered by a surface. This property is expressed in lumped component A discrete component (i.e.,
candelas per square meter (cd/m2). one that is self-contained). Compare DISTRI-
luminance channel In a color television circuit, BUTED COMPONENT.
the channel that processes the Y SIGNAL. lumped constant The total value of any single
luminance signal See Y SIGNAL. electrical property in an electrical or electronic
luminescence The production of visible light, but component.
not heat, by a material stimulated by radiation or lumped-constant delay line A delay line having dis-
electron bombardment. See ELECTROLUMINES- crete capacitance and inductance components.
luminescent cell See ELECTROLUMINESCENT lumped impedance A reactance and/or resistance
CELL. manifested in a definite location. Examples are
luminescent screen A cathode-ray tube whose ordinary components, such as capacitors, induc-
screen is coated with a material that glows under tors, and resistors.
the influence of ionizing radiation, X rays, or elec- lumped inductor See DISCRETE INDUCTOR.
tron beams. lumped parameter Any circuit parameter that can
luminiferous ether See ETHER, 1. be considered as a discrete parameter”even if it
luminosity The luminous efficiency of radiant en- is not made up of a single component.
ergy, as given by the ratio of luminous flux to ra- lumped resistor See DISCRETE RESISTOR.
diant flux (lumens per watt) for a specific lutetium Symbol, Lu. A metallic element of the
wavelength. rare-earth group. Atomic number, 71. Atomic
luminosity factor Abbreviated K, and expressed in weight, 174.967.
lumens per watt. The luminous intensity divided lux The unit of illuminance, equivalent to one LU-
by the actual radiant intensity at a given wave- MEN per square meter.
length of visible light. Luxemberg effect The generation of interference
luminous energy The energy in visible electromag- by cross-modulation of two or more signals
netic radiation. whose paths intersect in the same region of the
luminous flux The rate of transfer or flow of lumi- ionosphere.
nous energy. luxmeter A device for measuring visible illumi-
luminous intensity Luminous flux through a unit nance.
solid angle, expressed in candelas. Also see CAN- LV Abbreviation of LOW VOLTAGE.
lumistor An amplifier or coupling device in which ENTIAL TRANSFORMER.
the input signal varies the brilliance of a lamp, Lw Symbol for LAWRENCIUM; more commonly Lr.
electroluminescent cell, or light-emitting diode, lx Abbreviation of LUX.
and a photocell (or other light-sensitive device) LX band A section of the L BAND that extends from
picks up the fluctuating light and uses it to mod- 950 MHz to 1.15 GHz.
ulate an output current. In a compact lumistor, LY band A section of the L BAND that extends from
the light-emitting and light-sensing components 725 to 780 MHz.
are separate layers in a wafer or block of material. LZ band A section of the L BAND that extends from
Compare LIGHT AMPLIFIER. 1.450 to 1.550 GHz.
lumped Pertaining to a property that is concen- LZT Abbreviation of LEAD ZIRCONATE-TITANATE,
trated at or around a single point, rather than be- a ceramic used in electronics.
M 1. Abbreviation of prefix MEGA-. 2. Symbol for machine language Computer program instruc-
MUTUAL INDUCTANCE. 3. Symbol for MODI- tions and data represented in binary form. In the
FIED INDEX OF REFRACTION. hierarchy of programming languages, it is the
m 1. Abbreviation of prefix MILLI-. 2. Symbol for lowest; the computer works directly with it. All
MASS. 3. Abbreviation of METER. 4. Abbrevia- high-level languages are translated to machine
tion of MILE. (Also, mi.) 5. Symbol for MODULA- language by an assembler, compiler, interpreter,
TION COEFFICIENT. or monitor system.
m2 Abbreviation of square meter, the SI unit of machine learning In artificial intelligence, a com-
area. puter™s ability to learn through repeated calcula-
m3 Abbreviation of cubic meter, the SI unit of vol- tions for particular problems.
ume. machine logic 1. The way that a computer™s func-
MA 1. Abbreviation of MAGNETIC AMPLIFIER. tional parts are interrelated. 2. The facility
(Also, magamp.) 2. Abbreviation of MEGAMPERE. whereby a computer solves problems.
mA Abbreviation of MILLIAMPERE. machine operation The performance by a com-
Mache unit A unit of radioactivity equivalent to puter of a built-in function (e.g., subtraction).
13.47 disintegrations per second (3.64 — 10“10 machine operator A person participating in imple-
curie) per liter. It represents the concentration of menting and overseeing the processing of com-
radon gas per liter (when all radiation is ab- puter programs.
sorbed) that will result in a saturation current of machine word In computer operations, the ad-
10“3 esu (not to be confused with MACH NUM- dress of a memory location composed of the full
BER). number of bits normally handled by each register
machine address See ABSOLUTE ADDRESS. of the machine.
machine code See MACHINE LANGUAGE. machining In industrial robotics, the mechanical
machine cycle In a machine whose operation is modification of parts during assembly. Examples:
periodic, a complete sequence constituting a pe- drilling, welding, sanding, polishing, and paint-
riod of operation. ing.
machine error In a computer or data-processing Mach number For a medium such as air, the ratio
system, an error attributable to a hardware fail- of the speed of a body in motion to the speed of
ure, rather than to a software fault. sound in the medium. (Not to be confused with
machine instruction A computer program in- MACHE UNIT.)
struction written in MACHINE LANGUAGE. macro 1. A control shortcut, in which a function
machine knowledge General term for data stored requiring the actuation of several switches is ab-
in an artificially intelligent computer system, and breviated, via a microcomputer, so that it can be
the ability of the computer to use that data in executed by actuating only one or two switches.
meaningful ways. 2. Abbreviation of MACROINSTRUCTION.

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macro- • magnetic balance

macro- Prefix denoting extremely large. Compare magnetic amplifier An iron-core device that uses
MICRO-. the principle of the saturable reactor to obtain
macro assembly program An assembly program amplification. In its simplest form, it consists of
whose source statements are translated to sev- input and output coils wound on a core of
eral machine-language instructions. square-loop magnetic metal. The input coil con-
macroinstruction A source program instruction sists of two identical windings connected in
that becomes several machine-language instruc- series-opposition so that currents in the output
tions when operated on by a compiler. winding cannot induce voltage in the input wind-
macroknowledge In artificial intelligence, knowl- ing. The output coil is connected in series with a
edge in the large sense (i.e., knowledge about in- load and an alternating-current (ac) supply. A
formation). Example: a set of definitions in an small ac signal applied to the input winding
expert system. Compare MICROKNOWLEDGE. causes a large change in the impedance of the
macroprogram A computer program consisting of output winding and, therefore, a large change in
macroinstructions. the voltage across the load.
macrosonics The theory and applications of high-
amplitude sound waves.
madistor A component that produces changes in
current by means of magnetic-field effects. It is Load
used as an oscillator or amplifier.
magamp Acronym for MAGNETIC AMPLIFIER.
magazine A tape or film cartridge.
magenta One of the primary pigments used in
color printers. It has a pinkish-red hue.
magnal CRT base An 11-pin base typical of many
cathode-ray tubes.
magnesium Symbol, Mg. A metallic element.
Atomic number, 12. Atomic weight, 24.305.
magnesium fluoride phosphor A substance used
as a phosphor coating on the screen of a very-
long-persistence cathode-ray tube. The fluores-
cence and phosphorescence are orange. input
magnesium silicate phosphor A substance used
as a phosphor coating on the screen of a cathode-
ray tube. The fluorescence is orange-red.
magnesium tungstate phosphor A substance magnetic amplifier
used as a phosphor coating on the screen of a
cathode-ray tube. The fluorescence is very light
blue. magnetic analysis See MASS SPECTROMETER.
magnet A device or body of material that has the magnetic attraction 1. The force that causes a
ability to attract to itself pieces of iron and other magnetic pole to draw to itself an opposite mag-
magnetic metals, and the ability to attract or re- netic pole. Thus, a north pole attracts a south
pel other magnets. Also see ELECTROMAGNET, pole, and a south pole attracts a north pole. Com-
NET. causes a magnetic pole to draw to itself a piece of
magnet armature See KEEPER. magnetic material, such as iron or steel.
magnet battery A group of several magnets placed magnetic axis A straight line joining the poles of a
together in parallel (i.e., with similar poles touch- magnet.
ing or resting nearby) to act as a single magnet. magnetic bearing The azimuth, or compass direc-
magnet charger A device that produces an intense tion, measured with respect to magnetic north
magnetic field for restoring weakened magnets or (the direction of the north geomagnetic pole). It is
for making new magnets. usually expressed in degrees and can be read di-
magnetic 1. Pertaining to MAGNETISM. 2. Pos- rectly from a compass.
sessing MAGNETISM. 3. Capable of being magne- magnetic azimuth An azimuth bearing relative to
tized. 2. See MAGNETIC MATERIAL. magnetic north (the direction of the north geo-
magnetic air-gap A space between two magnetic magnetic pole).
poles, either the same (in which case the force is magnetic balance An instrument for measuring
repulsive) or opposite (in which case the force is the force, either attractive or repulsive, between
attractive). two objects that are magnetized, or between a
426 magnetic balance • magnetic field intensity

magnet and a magnetic substance. The device magnetic coupling See INDUCTIVE COUPLING.
can also be used for measuring the intensity of a magnetic course In navigation, a course refer-
magnetic field, either from a permanent magnet, enced to geomagnetic north, rather than geo-
an electromagnet, or from the earth. graphic north.
magnetic bias A steady magnetic force applied to magnetic crack detector See ELECTROMAG-
another magnetic field to set the latter™s quies- NETIC CRACK DETECTOR.
cent point (e.g., sensitizing a relay by using a per- magnetic creeping A gradual increase in the mag-
manent magnet to lower the relay draw-in point). netization of a material under the influence of a
magnetic blowout 1. The extinction of an electric steady magnetizing force.
arc by a strong magnetic field. 2. The apparatus magnetic cycle 1. For a material in an alternating
for accomplishing the action described in 1. magnetic field, the change in magnetic flux as a
magnetic bottle A container envisioned for atomic function of time. 2. The change in the magnetic-
fusion reactions, and that would consist of a field polarity of the earth. This polarity reverses
magnetic field. Conventional containers cannot every few thousand years.
withstand the extremely high temperatures in- magnetic damping The production of a damping
volved in atomic fusion. effect or drag in a machine or meter by means of
magnetic braking See ELECTROMAGNETIC magnetic action on a moving member, in accor-
BRAKING. dance with LENZ™S LAW.

magnetic bridge An instrument comparable to the magnetic declination See DECLINATION.
WHEATSTONE BRIDGE, used to measure mag- magnetic deflection See ELECTROMAGNETIC

netic permeability. DEFLECTION.
magnetic bubble memory See BUBBLE MEM- magnetic density The concentration of magnetic
ORY. flux in a region, expressed as the number of lines
magnetic capacity The maximum magnetization a per unit area of cross section.
given material can receive. magnetic dip At a particular location on the
magnetic card A computer storage medium in the earth™s surface, the angle between the terrestrial
form of a card that can be selectively magnetized magnetic field and a horizontal line.
or imprinted with magnetic ink to represent data. magnetic dipole 1. A molecule or particle with a
magnetic cartridge A variable-reluctance phono- north and south magnetic pole. 2. Any pair of ad-

graph pickup. As the stylus moves in the groove, jacent north and south magnetic poles.
the vibrations are translated into electric cur- magnetic direction finder Abbreviation, MDF. A
rents by a magnet and coil. type of compass operated by an electric signal de-
magnetic centering Centering the beam in a tele- livered by a gyrostabilized magnetic-compass
vision picture tube by means of an electromag- movement.
netic focusing coil, a permanent magnet, or both. magnetic disk A rotating disk coated with a layer
magnetic character A letter, numeral, or other of magnetic material for the recording, storage
symbol written or printed in (visible) magnetic ink and retrieval of information. They are available in
for its automatic sensing or reading in computing various sizes, configurations, and storage capaci-
and signaling operations. ties. Commonly used with personal computers.
magnetic circuit The closed path determined by a Also see DISKETTE and HARD DISK.
line of magnetic flux or by a set of lines of flux. magnetic doublet See DOUBLET, 2.
magnetic clutch A clutch in which the magnetism magnetic drive A device in which mechanical
of one rotating member causes a second member movement is conveyed from one moving part to
to lock in and rotate. There need not be physical another by means of a magnetic clutch.
contact between the two. magnetic drum See DRUM.
magnetic coil The winding in an electromagnet or magnetic effect of electric current The presence
similar device. of a magnetic field around a conductor carrying
magnetic compass A direction-indicating device electric current.
using a horizontally suspended magnetic needle magnetic equator Also called geomagnetic equator.
as the indicator. The needle tends to point in the An imaginary circle around the earth, along which
direction of the north geomagnetic pole. Com- a magnetic needle shows no dip. It is near, but
pare GYROCOMPASS. slightly displaced from, the geographic equator,
magnetic component See ELECTROMAGNETIC and is midway between the geomagnetic poles.
COMPONENT. magnetic feedback Feedback by means of induc-
magnetic conductivity See PERMEABILITY. tive coupling between the output and input cir-
magnetic constant The absolute permeability of cuits of a system. It can be positive or negative.
free space. It is approximately 1.26 — 10“6 H/m. magnetic field The space around a magnetic pole
magnetic controller A controller that uses electro- or magnetized body in which magnetic energy
magnets for some of its functions. acts.
magnetic core The iron core of an electromagnet, magnetic field intensity See MAGNETIC INTEN-
choke, transformer, relay, or similar device. SITY.

magnetic field strength • magnetic media

’ +



magnetic flux

magnetic gap A space separating the materials in
a magnetic circuit. This break is either an air
space or one filled with a comparatively thin piece
of nonmagnetic material (e.g., the gap in a choke-
coil core).
magnetic head See MAGNETIC PICKUP HEAD
magnetic hysteresis See HYSTERESIS, 1.
magnetic inclination See MAGNETIC DIP.
magnetic feedback magnetic induction 1. The magnetization of a
magnetic material, such as iron or steel, when it
magnetic field strength See MAGNETIC INTEN- is placed in a magnetic field. 2. The induction of
SITY. an alternating voltage in a conductor by a nearby
magnetic-field viewer A device for visually exam- alternating magnetic field. Also see ELECTRO-
ining a magnetic field. It consists of a clear plas- MAGNETIC INDUCTION.
tic watchcase filled with iron-oxide particles in magnetic ink Writing or printing ink that is a sus-
liquid suspension. When it is placed within a pension of finely divided particles of magnetic
magnetic field, the particles align themselves in material. Also see MAGNETIC CHARACTER.
the direction of the magnetic lines of flux. magnetic instability 1. The tendency of a mag-
magnetic-film memory A magnetic memory in netic recording medium to deteriorate with time.
which memory cells consist of a thin film (thick 2. Any fluctuation in the intensity of a magnetic
film in some instances) of a magnetic material de- field.
posited on a substrate. Information is written into magnetic intensity The free-space strength of a
and read out of the cell through coils. Also called magnetic field at a particular point. Specifically,
thin-film memory. the force (in dynes) that the magnetic field would
magnetic flip-flop A bistable multivibrator using exert on a unit magnetic pole placed at that point.
magnetic amplifiers or square-loop cores in place magnetic iron oxide See MAGNETITE.
of transistors. magnetic leakage The usually undesired exten-
magnetic flux The intensity of a magnetic field sion of magnetic flux beyond the confines of a
through a given area. The unit of magnetic flux is magnetic body, such as the core of a choke.
the weber, and the symbol is F. It can loosely be magnetic lens See ELECTROMAGNETIC LENS.
expressed as the number of lines passing through magnetic line of flux See LINE OF FLUX, 2.
a region of a certain area or of a unit area, such magnetic load An electromagnetic device operat-
as one square meter. See FLUX. ing on the output of an electrical source. Such de-
magnetic flux density See FLUX DENSITY. vices include actuators, alarms, electromagnets,
magnetic flux linkage The passage of magnetic magnetic tapes and disks, relays, and loudspeak-
lines of flux through separate materials or cir- ers.
cuits, thereby coupling them magnetically. magnetic loudspeaker See MAGNETIC SPEAKER,
magnetic focusing See ELECTROMAGNETIC FO- 1, 2.
CUSING. magnetic material 1. A material, such as mag-
magnetic force The force exerted by a magnet on a netite, that exhibits natural magnetism. 2. A ma-
body of magnetic material, or on another magnet, terial, such as iron or steel, that is capable of
within its field. being magnetized.
magnetic friction 1. See HYSTERESIS, 1. 2. The magnetic media Any medium that stores data as
resistance experienced by a magnetic material tiny magnetic fields; in particular, MAGNETIC
moving in a magnetic field. DISK or MAGNETIC TAPE.
428 magnetic memory • magnetic shielding

magnetic memory 1. See RETENTIVITY. 2. A dig-
ital memory circuit using magnetic fields to store
data bits. Example: BUBBLE MEMORY.
magnetic meridian The circle of the celestial
sphere that passes through the zenith and
earth™s magnetic poles.
magnetic mine A naval mine detonated by a mag-
netic switch that is closed by the proximity of the
steel hull of a ship. Tape
magnetic modulator A core-type device that is
somewhat similar to a magnetic amplifier used
for amplitude modulation. Modulating current
passes through the control winding, and the car-
rier current through the output winding.
magnetic moment Unit, joule per tesla. For a
magnet, the product of pole strength and the dis-
Motion of tape
tance between poles.
magnetic needle The pivoted magnetic pointer in
magnetic recording
a magnetic compass.
magnetic north See NORTH MAGNETIC POLE.
magnetic oxide Iron oxide used as the sensitive such as a magnetic disk or tape. 2. A magnetic
coating of magnetic recording tape. medium on which data has been recorded.
magnetic pickup 1. A phonograph pickup of the magnetic recording head In a tape recorder, the
variable-reluctance type (see VARIABLE-RELUC- transducer that receives current impulses
TANCE PICKUP). 2. A magnetic transducer (such (analogs of the original sound vibrations) from an
as a phono cartridge, tape recording head, or amplifier and converts them into magnetic im-
similar input element). pulses that magnetize spaces on the passing
magnetic-pickup head In a tape recorder, the tape. Compare MAGNETIC PICKUP HEAD.
transducer that receives up magnetic impulses magnetic recording medium 1. A magnetic cylin-
from the passing tape and converts them into al- der, disk, drum, tape, or wire used in the record-
ternating currents. These currents are amplified ing of sound or data. 2. The sensitive material
to obtain the original sound. Compare MAG- with which any of these is coated.
NETIC RECORDING HEAD. magnetic relay A relay having a permanent mag-
magnetic-plate wire Wire in which a magnetic net in whose field a coil, bar, or reed moves to
metal has been plated on top of a nonmagnetic open or close a pair of contacts.
metal. magnetic remanence See RESIDUAL MAG-
magnetic poles 1. The points in a MAGNET at NETISM.
which the magnetic lines of flux converge. 2. The magnetic repulsion The force that causes a mag-
points on the earth at which the geomagnetic netic pole to push away a similar magnetic pole,
lines of flux converge. See NORTH MAGNETIC although they are not in mutual contact. Thus,
POLE and SOUTH MAGNETIC POLE. two north poles repel each other, and so do two
magnetic pressure See MAGNETOMOTIVE south poles. Compare MAGNETIC ATTRACTION.
FORCE. magnetic-resonance accelerator See CYCLO-
magnetic printing 1. Also called magnetic print- TRON.
through. In a recording material, such as mag- magnetics 1. Collectively, magnetic components
netic tape, the transfer of information from one and equipment. 2. Collectively, magnetic materi-
part of the material to another part (or from one als. 3. A branch of physics dealing with magnets
medium to another) by the magnetic field of the and magnetism.
recorded material. This phenomenon, which is magnetic saturation The condition in which a
also called PRINT-THROUGH, sometimes occurs magnetic material passes all of the magnetic lines
in recording tape on a reel. 2. Conventional of flux that its permeability allows. Increasing the
lithography, letterpress, or other reproduction intensity of the magnetizing force will produce no
process in which MAGNETIC INK is used. increase in magnetization.
magnetic print-through See MAGNETIC PRINT- magnetic scan See ELECTROMAGNETIC DE-
magnetic probe A loop or coil inserted in an elec- magnetic screen See ELECTROMAGNETIC
tromagnetic field to sample the magnetic compo- SHIELD.
nent. See, for example, WAVEGUIDE PROBE. magnetic shield See ELECTROMAGNETIC
magnetic recording 1. The recording of sounds or magnetic shielding 1. Enclosing a magnetic field
data by varying the magnetization of a medium, to confine its flux, thus preventing interaction
magnetic shielding • magnetic whirl

with outside bodies. 2. Devices (such as boxes, Lack of uniformity in output then serves as an er-
cans, or shells of iron, steel, or a magnetic alloy) ror indicator. The original quantity is recovered
used for the purpose described in 1. by dropping the extra bit following a parity check.
magnetic shift register A shift register using mag- magnetic tape reader A tape deck for playing back
netic flip-flops. data on magnetic tape.
magnetic shunt A device that allows the useful magnetic tape recorder A recorder-reproducer
magnetic flux of an instrument™s magnet to be using magnetic tape.
controlled. The device consists of a piece of mag- magnetic test coil See SEARCH COIL.
netic material near the magnet in an electrical magnetic thick film A film of magnetic material at
least 10-6 meter in thickness, deposited on a sub-
measuring instrument.
magnetic south See MAGNETIC SOUTH POLE. strate. Compare MAGNETIC THIN FILM.
magnetic speaker 1. A loudspeaker that is essen- magnetic thin film A film of magnetic material,
less than 10-6 meter in thickness, deposited on a
tially an enlarged earphone with a horn that con-
veys and intensifies the sound from the vibrating substrate. Compare MAGNETIC THICK FILM.
diaphragm. 2. A loudspeaker in which the vibra- magnetic transducer A transducer that uses a
tion of a diaphragm or reed in the field of a per- coil, magnet, or both, to convert displacement
manent magnet is conveyed by a pin to a paper or into variable magnetic fields or electric currents.
composition cone. Compare DYNAMIC SPEAKER. Common varieties are the inductance type, trans-
magnetic storage 1. A data bank or memory that former type, and generator type. Compare
stores information in the form of magnetic fields. CAPACITIVE TRANSDUCER, CRYSTAL
2. The data on a magnetic tape or disk. TRANSDUCER, and INDUCTIVE TRANSDUCER.
magnetic storm A disturbance in the earth™s mag- magnetic tuning In a microwave oscillator, a
netic field that typically follows a solar flare. Of- means of tuning in which a ferrite rod in the cav-
ten causes interference to radio communications ity resonator is made to have adjustable magneti-
at low, medium and high frequencies. zation so that the resonant frequency of the
magnetic strip A strip of powdered iron or ferrite cavity varies and the frequency of the oscillator is
on the back of an identification card, bank cash thus adjustable. It is also used at ultra-high fre-
card, or credit card, that carries a code to identify quencies (UHF) and occasionally at very-high fre-
the account number and verify that the secret en- quencies (VHF).
try code (if any) is correct, or that the credit is magnetic-vane meter See IRON-VANE METER.
good. magnetic vector In an electromagnetic field, the
magnetic susceptibility See SUSCEPTIBILITY. vector representing the magnetic component. It is
magnetic switch 1. In security systems, a switch perpendicular to the electric vector.
kept open by the presence of a magnet attached magnetic viscosity A property of certain materi-
to a door, window, or other movable object. When als, described in terms of the time required to
the object is moved, the magnet moves away from magnetize a given substance to a specified level.
the switch, closing the switch and actuating an magnetic whirl One of the circular magnetic lines
alarm. 2. A REED SWITCH operated by a mag- of flux around a straight conductor that carries
netic field. electric current.
magnetic tape Plastic tape coated with a film of
magnetic material; it can be magnetized along its
length to record sounds, video signals, and com-
puter information.
magnetic-tape core A strip of magnetic metal
wound spirally to create a toroid (donut) shape.
Such construction is sometimes used in choke or Current-carrying
transformer cores. Also see TOROID. wire
magnetic tape deck See TAPE DECK.
magnetic tape drive See TAPE TRANSPORT.
magnetic tape head See MAGNETIC PICKUP
magnetic tape library In a computer installation,
the place where magnetic tape files are kept, or
magnetic tape files and the records needed to uti-
lize them.
magnetic tape parity As a safeguard against los-
ing information bits during the transfer of infor-
mation between magnetic tape and a memory
device, a technique in which an extra bit is gener-
ated and added to characters under certain con-
magnetic whirl
ditions, to make the output uniform temporarily.
430 magnetic wire • magnetostriction

magnetic wire The thin wire used in wire record- magnetohydrodynamic generator A device using
ing and playback. See WIRE RECORDER. magnetohydrodynamic principles to generate
magnetism The property of having or causing a electric power directly from gases. In the genera-
magnetic field. It occurs when magnetic dipoles tor, a hot gas is passed through an intense mag-
are aligned and when electric charge carriers are netic field; a pair of collector plates picks up
in motion. electrons from the ionized gas.
magnetite A natural magnetic oxide of iron. Also magnetohydrodynamic gyroscope A gyroscope
called LODESTONE. whose spin is obtained by a rotating magnetic
magnetization curve A curve depicting the mag- field circulating a conducting fluid, such as mer-
netization of a material versus the applied mag- cury, around a closed loop. Also see MAGNETO-
netizing force. See, for example, HYSTERESIS HYDRODYNAMICS.
CURVE. magnetohydrodynamic power generator See
magnetizer A device for magnetizing magnetic ma- MAGNETOHYDRODYNAMIC GENERATOR.
terials, as in the making of permanent magnets. magnetohydrodynamics Abbreviation, MHD. The
Also see MAGNET CHARGER. Compare DEMAG- theory and application of phenomena produced
NETIZER. by electrically conductive fluids and gases in elec-
magnetizing current 1. A current that sets up a tric and magnetic fields.
magnetic field of useful intensity. 2. The half- magnetometer An instrument for measuring the
cycle of an alternating current or the polarity of a strength and direction of magnetic fields.
direct current flowing through a coil wound on a magnetomotive force Abbreviation, mmf. Unit,
permanent magnet (as in a headphone, perma- ampere. The phenomenon that is sometimes de-
nent-magnet loudspeaker, or polarized relay) that scriptively called magnetic pressure. It is analo-
increases magnetic field strength. Compare DE- gous to electromotive force (and to water
MAGNETIZING CURRENT. 3. The field current of pressure) and is the agent that produces a mag-
a dynamo. netic field.
magnetizing force 1. Magnetomotive force (in magneton See BOHR MAGNETON.
gilberts) divided by spatial distance (in meters). 2. magneto-optical rotation The tendency of a mag-
The intensity of a magnetic field that causes a netic field to rotate the plane of polarization of
material to become magnetized. light passing through a substance. Also see
magnet meter See MAGNET TESTER. magneto-optical technology A computer data-
magnet motor See PERMANENT-MAGNET MOTOR. storage technology that uses lasers to guide the
magneto See PERMANENT-MAGNET GENERATOR. read/write head in a magnetic disk drive. This
magnetocardiogram Abbreviation, MCG. A record, greatly increases the amount of data that can be
made by a MAGNETOCARDIOGRAPH, of the pul- effectively stored on, and retrieved from, a mag-
sating magnetic field of the heart. It is used as a netic disk.
diagnostic aid. magneto-optical valve See KERR MAGNETO-
magnetocardiograph An instrument that pro- OPTICAL EFFECT.
duces a record of the pulsating magnetic field magnetopause The high-altitude limit of the MAG-
generated around the torso by natural ion cur- NETOSPHERE.
rents in the heart. magnetoplasmadynamics See MAGNETOHYDRO-
magnetoelectric generator See MAGNETOGEN- DYNAMICS.
ERATOR. magnetoresistance The phenomenon whereby the
magnetofluid mechanics See MAGNETOHYDRO- resistance of a material, such as a semiconduc-
DYNAMICS. tor, changes when it is exposed to a magnetic
magnetofluidynamics See MAGNETOHYDRODY- field. Also see MAGNETORESISTOR.
NAMICS. magnetoresistor A material (such as bismuth
magnetogasdynamics See MAGNETOHYDRODY- wire, indium antimonide, or indium arsenide)
NAMICS. whose resistance varies with the strength of a
magnetoionic duct A propagation path for radio magnetic field in which it is placed.
waves between two points that have the same magnetosphere In the upper atmosphere, a region
geomagnetic longitude on the surface of the extending thousands of kilometers from the
earth. The radio waves tend to travel with the ge- earth, in which charged particles are trapped by
omagnetic lines of flux at some frequencies under the earth™s magnetic field.
certain conditions. magnetostatic field A stationary magnetic field,
magnetoionics The study of the effects of the geo- such as that produced by a permanent magnet.
magnetic field on the propagation of radio waves. magnetostriction The expansion or contraction of
magnetogenerator See PERMANENT-MAGNET a bar or rod of magnetic material (such as Invar,
GENERATOR. Monel metal, Nichrome, nickel, or Stoic metal) in
magnetograph An instrument for automatically proportion to the strength of an applied magnetic
recording a magnetic field. field. Magnetostrictive vibration in such a rod is
magnetostriction • main memory

evated temperature) inside the body, as in heat-
Charged cosmic
particle ing a cancerous tumor for therapeutic purposes.
magnetron A microwave vacuum tube consisting
of a diode (with a cylindrical anode) through
which the field of a powerful external permanent
magnet passes. The magnetic field causes elec-
trons leaving the cathode to travel in spiral paths
Magnetosphere between the electrodes. This action gives the tube
a negative-resistance characteristic, resulting in
oscillation when the tube is connected in an ap-
propriate circuit. Some magnetrons have a built-
in resonant cavity.

plate Cathode
comparable to piezoelectric vibration in a quartz ’’ ’+
crystal. Plate
magnetostriction filter See ULTRASONIC FIL-
TER, 1. Magnets
magnetostriction oscillator An oscillator whose
frequency is controlled by a magnetostrictive rod magnetron
(see MAGNETOSTRICTION). The dimensions of
the rod and the type of metal it contains deter-
magnet steel A high-retentivity alloy of chrom-
mine its vibration frequency and, accordingly, the
ium, cobalt, manganese, steel, and tungsten,
operating frequency of the oscillator.
used in the manufacture of permanent magnets.
magnet tester An instrument used to measure the
flux of a magnet. Also see FLUXMETER.
magnet wire Insulated wire (usually solid copper)
of 14 to 40 gauge, so called because of its original
major use in winding the coils of electromagnets.
+ magnitude 1. General expression for degree, size,
or extent. 2. Signal strength (amplitude). 3. For a
’ number or vector quantity, the absolute value or
length. 4. A measure of the relative or absolute
brightness of celestial objects.
mAh Abbreviation of milliampere-hour.
main British expression for the alternating-current
magnetostriction oscillator
(ac) utility power available in a house or building.
main bang 1. In a radar display, the pip or pulse
magnetostrictive delay line A delay line in which resulting from the actual transmitted signal. This
the signal is propagated through a magnetostric- pulse is blanked out. 2. In a spectrum analyzer,
tive rod. Also see MAGNETOSTRICTION. the pip corresponding to a frequency of zero, and
magnetostrictive microphone A microphone in caused by the local oscillator.
which sound vibrations produce changes in a mainframe 1. The chassis containing the central
magnetostrictive element, which, in turn, are processor and arithmetic and logic circuits for a
converted into output-voltage changes. Also see large computer. 2. The general term for a large,
MAGNETOSTRICTION. powerful computer.
magnetostrictive transducer A transducer in main lobe Also called major lobe. In a directional
which some phenomenon, such as vibration or antenna system, the portion of the directivity pat-
pressure, produces changes in a magnetostriction tern representing the greatest transmitted signal
element, which in turn are converted into output- gain and/or the greatest received signal re-
voltage changes. Also see MAGNETOSTRICTION. sponse. Also see MINOR LOBE, SIDE LOBE.
magnet protector See KEEPER. main memory The principal (immediate process)
magnetrode The trademark of a radio-frequency memory unit in a digital computer or data-
device for externally producing hyperthermia (el- processing system.
432 main path • manual

system (e.g., major feedback loop). Compare MI-
make 1. The closing of a pair or set of contacts.
2. To close a pair or set of contacts.
make-before-break contacts A pair of contacts in
which the movable arm closes with the next con-
tact before breaking with the previous one. Com-
make time The time required for a relay to latch
completely, or for a switch (either mechanical or
electronic) to close completely. Compare BREAK
male plug A plug having one or more protruding
contacts in the form of pins, blades, or prongs.

male plug

main path In a computer program, the sequence of Malter effect The tendency for a layer of semicon-
instruction execution disregarding the execution ductor having a high secondary emission ratio to
of subroutines. become positively charged when bombarded by
main program The part of a computer program electrons. This occurs when a thin insulator sep-
other than a subroutine. arates the semiconductor from a metal plate. The
insulator must be very thin (on the order of 10“7
main routine See MAIN PROGRAM.
mains 1. In a power-distribution center, the lines meters). This results in a potential difference of
that supply the entire system. An example is the up to about 100 volts.
set of lines leading into a house. 2. The utility wires manganese Symbol, Mn. A metallic element.
and associated outlets in a house or building. Atomic number, 25. Atomic weight, 54.938.
maintenance The process of keeping a system, cir- manganese-dioxide depolarizer In a dry cell,
cuit, or component in operating condition, with manganese dioxide mixed with powdered carbon,
minimal down time. the mixture being a depolarizing agent. Also see
maintenance routine A computer program used DEPOLARIZER.
by computer service personnel for diagnosis dur- manganin A low-temperature-coefficient alloy
ing a regular service interval. used in making wire for precision resistors. A typ-
major beats The principal beats produced in a ical composition is: copper (84 percent), man-
beat-note system; they are usually the sum ganese (12 percent), and nickel (4 percent).
and/or difference of two fundamental frequen- manipulator A robot arm and end effector, as used
cies. Compare MINOR BEATS. in mechanical processes.
major face In a hexagonal quartz crystal, one of man-made interference See HUMAN-MADE IN-
the three larger faces. Compare MINOR FACE. TERFERENCE.
majority carrier The predominant charge carrier man-made static See HUMAN-MADE INTERFER-
in processed semiconductor material. Electrons ENCE.
are the majority carriers in n-type material; holes manometer An instrument for measuring gas or
are the majority carriers in p-type material. Com- vapor pressure”especially at low levels.
pare MINORITY CARRIER. manpack A portable radio transceiver that can be
majority logic A logic gate in which the output is used while walking.
high whenever the majority of its inputs is high, mantissa 1. The portion of a logarithm to the right
regardless of which inputs are high. Thus, in a of the decimal point. Thus, in 3.952502 (log10
five-input gate of this type, the output is high 8964), the mantissa is 0.952502. 2. The fixed
when any three or more of the inputs are high. point part of a number in scientific notation;
thus, in 4 — 103, the mantissa is 4.
major lobe See MAIN LOBE.
major loop The principal path for the circulation of manual 1. Actuated or operated directly by me-
information or control signals in an electronic chanical means, rather than automatically. 2. A
manual • maser

book, or a set of online information files, detailing marker 1. A pip that indicates a particular fre-
the operation and maintenance procedures for a quency on a response curve displayed on an os-
device or system. cilloscope screen. 2. A character that identifies
manual input Use of a keyboard, mouse, trackball, the end of a data set. Also called MARK (see
or other electromechanical input device to enter MARK, 4).
data into a computer program or system. marker beacons Individual coded-signal transmit-
manual operation In data processing, an opera- ters placed along a radio range and indicating
tion in which automatic machines are not in- features of the course marked by them.
volved. marker frequency 1. A known frequency that can
manual telegraphy Telegraphy that consists sig- be used to identify a spot-frequency harmonic of
nals transmitted by a hand-operated key and a frequency-standard signal. 2. A known accu-
recorded by hand (pen, pencil, or typewriter). rate signal used to identify the limit of a radio
manual tuning Tuning performed entirely by ad- band. 3. The frequency at some point on a re-
justing variable circuit components by hand. sponse curve as identified by a marker pip (see
manual word generator A device by which an op- MARKER).
erator can originate information words for input marker generator An oscillator that supplies a
into computer memory. marker pip (see MARKER).
manufacturing automation protocol In a factory mark hold In telegraphy, an unmodulated signal
using computer-controlled robots, the set of stan- meaning information is not being sent.
dards for data communication between the mark reading The reading by an optical scanning
robots and the controller and/or between individ- device of marks made in specific areas of a docu-
ual robots. It keeps the factory operating ment; the process also includes the marks™ con-
smoothly. version to digital signals for input to a computer.
MAR Abbreviation of MEMORY-ADDRESS REGIS- mark scanning See MARK READING.
TER. mark sensing A process similar to MARK READ-
Marconi antenna A quarter-wave radio transmit- ING, except that the marks are sensed electri-
ting or receiving antenna operated against an cally.
earth ground. marker trap A wave trap that supplies a dip-type
Marconi effect The undesired tendency of an en- marker pip when used in conjunction with a ra-
tire receiving antenna system, including lead-in dio-frequency test oscillator (see MARKER).
or feeders, to act as a MARCONI ANTENNA. market scanner Also called bar-code reader. A de-
margin 1. A gap or space between two objects, vice that scans a black-bar binary label printed
such as adjacent plates of a capacitor. 2. Clear- on a carton or other package (or magazine), and
ance. 3. The maximum error that can be tolerated indicates the price of the merchandise on the
without risk of improper or abnormal operation. readout of the checkout register.
4. In a teletypewriter, the range of adjustments in mark-to-space ratio In radiotelegraphy, the ratio
which the error frequency is acceptable. of the duration (mark) of a dot to the interval
marginal relay A relay having a small difference (space) between successive dots.
between its on and off currents or voltages. Marx generator An impulse-type high-voltage
marginal test As performed on equipment in a direct-current generator circuit in which several
computer installation, a test to either determine capacitors are charged in parallel through a high-
the cause of an intermittent malfunction, or ver- resistance network. When the capacitor voltage
ify an equipment™s operating tolerances. reaches a critical high value, discharge occurs in
marine broadcast station A coastal station that series through spark gaps, producing a high-
broadcasts information of interest to shipping: voltage pulse for each discharge.
time, weather, ocean currents, etc. maser A low-noise microwave amplifying device in
marine radio Radio communications between which a microwave input signal causes high-
seagoing vessels or between vessels and shore energy-state molecules of ammonia or ruby to fall
stations. to the low-energy state and, as a result, to emit
marine radiobeacon station A land-based radio- large amounts of energy as an output signal. The
navigation station whose transmitted signals are name is an acronym for microwave amplification
used for taking bearings. by stimulated emission of radiation.
mariner™s compass See MAGNETIC COMPASS.
mark 1. In telegraphy, the dot or dash portion of a
character, as opposed to the dead space between
such portions. 2. The intelligence part of a simi-
lar signal (such as sound, light, etc.). 3. The high ac input
(logic 1) state represented by a binary bit, as op-
posed to the low (logic 0) state. 4. A character
identifying the end of a data set. Also called
Marx generator
434 mask • master program file

mask 1. A kind of stencil through which plating, mass spectrometer Abbreviation, MS. An instru-
electrodeposition, or diffusion can be done. ment that permits rapid analysis of chemical
2. The viewing screen, or GRATICULE, of an oscil- compounds via the MASS SPECTRUM.
loscope. 3. To obliterate a signal with a stronger mass spectrum An electron spectrum that can be
one. 4. A bit or character pattern used to change used to identify a chemical element. Different ele-
or extract bit positions in another pattern. ments have nuclei with different charge-to-mass
masking 1. The use of a MASK of any type. 2. The ratios. This results in each element having a
tendency of one effect or phenomenon to obscure unique mass spectrum.
another. It applies especially in audio systems, mass storage In a computer system, a magnetic or
where certain sounds impair the ability of a lis- optical storage medium capable of holding large
tener to hear other sounds that occur at the same amounts of data. Examples: magnetic diskette,
time. 3. The extent to which one effect or phe- magneto-optical diskette, external hard disk,
nomenon obscures another. compact-disk read-only memory (CD-ROM), and
Masonite Masonite Corporation™s tough fiberboard magnetic tape.
used for panels and bases of some electronic mass unit See ATOMIC MASS UNIT.
equipment. master 1. The primary or main element or device
mass The quantity of matter in a body. Like weight, in a system. 2. A primary data medium or record-
mass is expressed in kilograms in the metric (SI) ing from which copies are made. 3. A primary
system and in pounds in the English system. For reference standard. See the following several
a given piece of material, mass can be determined definitions.
by dividing the weight by the acceleration of grav- master clock 1. In a digital computer, the primary
ity. generator of timing pulses. 2. A standard time
mass data Data in excess of the maximum amount clock that drives other (slave) clocks, or to which
that can be stored in the main (internal) storage clocks of lesser accuracy can be referred.
unit of a digital computer (i.e., that which can master console In a computer system, an equip-
only be accommodated by external media such as ment with panel instruments and controls, which
magnetic disks or tapes). permits operations to be governed, monitored,
mass-energy equation Energy (E) is the product of and controlled by a human operator.
a given mass (m) and the square of the speed of master control 1. The main control circuit in a
light (c2): E = mc2. It is also called the Einstein system. 2. A point from which signals or pro-
equation. grams are distributed in a communications or
mass number 1. Symbol, A. A number represent- broadcast system.
ing the total of neutrons and protons in the nu- master data Also called archives. In a computer
cleus of an atom. The approximate mass of an record, data elements that remain unaltered for a
atom is equal to A — mp, where mp is the total pro- long time, and from which copies are made.
ton (rest) mass. 2. The number indicating the master file A computer file of data used routinely
sum of nuclear protons and neutrons in an atom. and remaining unchanged for a long time.
It is usually written following the symbol for the master gain control The principal gain control in
atom: thus, U238 is uranium having 238 nucle- an audio amplifier or mixer [i.e., the one used to
ons. An isotope of an element will have a different adjust the gain (volume) of the entire system].
mass number than that of the normal atom. master instruction tape Magnetic tape on which
mass of electron at rest Symbol, me. The amount various related computer programs are recorded.
of matter in an electron; me = 9.1093897 — master library tape See MASTER PROGRAM FILE.
10“31 kg. master oscillator Abbreviation, MO. The main os-
mass of neutron at rest Symbol, mn. The mass of cillator in an electronic system (e.g., the oscillator
a neutron in the nucleus of an atom; mn = stage in an oscillator-amplifier type of radio
1.6749286 — 10“27 kg. transmitter). This oscillator can be either self-
mass of proton at rest Symbol, mp. The mass excited or crystal-controlled.
of a proton in the nucleus of an atom; mp = master oscillator-power amplifier Abbreviation,
1.6726231 — 10“27 kg. MOPA. A type of transmitter or signal generator
mass resistivity 1. The resistance of a wire one in which a frequency-determining oscillator
meter long having a mass of one gram. It varies, drives a power amplifier, which in turn delivers
depending on the composition of the wire. 2. The an output signal. Because the oscillator is iso-
resistance of a wire one mile long having a weight lated from the output load, this arrangement has
of one pound. It varies, depending on the compo- greater stability than one in which the oscillator
sition of the wire. alone supplies power to the load.
mass spectograph An instrument used to ana- master pattern The etching pattern used for man-
lyze chemical compounds and mixtures in ufacture of a batch of identical printed-circuit
terms of their distinctive mass spectra, exhib- boards.
ited by ionized samples of the materials in a master program file A reel of magnetic tape on
magnetic field. which is recorded the programs regularly used in
master program file • maxima and minima

a data-processing installation. It is also called 100

Current (amperes)
master library tape. 4

Voltage (volts)
master record In a data-processing system, the
current record (usually stored on a disk or tape) 3
that will be used for the next computer run.
Current 2
master relay A relay that operates other (slave) re-
lays. Compare SLAVE RELAY. 20 1
master station See KEY STATION.
0 0
master switch A switch that can actuate or deac-
Relative position
tuate an entire installation or system.
master tape 1. In sound recording and reproduc-
tion, a magnetic tape that contains material from
which other tapes and discs can be made. 2. In Gen. Load
(50 ohms)
automation, a magnetic tape on which is (50 ohms)
recorded the basic signal sequence for controlling
a process and other recorders. 3. In data pro- matched transmission line
cessing, a magnetic tape that must not be erased.
master volume control See MASTER GAIN CON-
TROL. mitted radiotelegraph signals. The carrier wave
masurium See TECHNETIUM. from the transmitter is rectified by a small semi-
MAT Abbreviation of MICROALLOY TRANSISTOR. conductor diode, whose direct-current output
match 1. To mate devices, signals, impedances, powers the oscillator.
etc. for optimum compatibility in terms of signal Mateucci effect The generation of a potential dif-
transfer, equipment interfacing, and other opti- ference in a helically wound, ferromagnetic wire
mizing qualities. 2. The condition of being com- when its magnetization fluctuates.
patibly mated, physically or electrically. mathematical check A test of the validity of the
matched components Circuit components (capac- result of an arithmetic process (by using alternate
itors, coils, diodes, resistors, transistors, etc.) methods, for example).
that are carefully selected for similar or particu- mathematical logic 1. A branch of mathematics
larly compatible operating characteristics. that involves the theoretical behavior of various
matched filter 1. A filter with input and output systems of reasoning. 2. See BOOLEAN ALGE-
impedances matched to the input line and output BRA. 3. See DIGITAL LOGIC.
load, respectively. 2. A filter designed for separat- mathematical model See MODEL, 2.
ing a signal with a particular waveform from mathematical subroutine Within a computer pro-
other signals and noise. gram, a subroutine serving as an arithmetic func-
matched impedance A usually non-reactive tion (i.e., one for performing an operation not
impedance that has the same value as that of an- integral to the monitor program).
other impedance with which it is operated. Maxi- matrix 1. A high-speed switching or memory array
mum power is transferred between impedances used in counters and computers. 2. Generally,
that are matched. any two-dimensional array of objects. 3. A device
matched load A purely resistive load, the im- for solving linear simultaneous equations, con-
pedance of which is the same as the character- sisting of a rectangular array of coefficients.
istic impedance of the feed line. This results in matrix printer See WIRE PRINTER.
optimum power transfer from the line to the load. mat switch A form of PRESSURE SENSOR used in
matched pair A pair of matched components of- some security systems. When weight appears on
fered in a single package. the mat, switches close, actuating an alarm.
matched transmission line A transmission line matter The building material of the universe that
terminated in a purely resistive impedance whose occupies space and has mass that can be mea-
value is identical to the characteristic impedance sured. See, for illustration, ATOMIC THEORY and
of the line. Such a line transfers all of its energy STATES OF MATTER.
to its load without reflection; no standing waves matter waves See DE BROGLIE WAVES.
are on the line. max Abbreviation of MAXIMUM.
matching pad An inductance-capacitance (LC) maxima Points along a curve at which a function
network for matching the impedance of a load to reaches a local maximum value. Also see MAX-
the output impedance of a signal generator. IMA AND MINIMA.
matching stub See STUB. maxima and minima 1. The loops and nodes of
matching transformer An audio-frequency (AF) or current or voltage on an antenna or transmission
radio-frequency (RF) transformer used to match line. 2. The lobes and nulls in a directivity pat-
one purely resistive impedance to another. tern. 3. The bright and dark bands in a visible-
matchtone A transistorized, single-frequency au- light interference pattern. 4. In radar reflections,
dio oscillator that can be used to monitor trans- regions of localized maximum and minimum
436 maxima and minima • Maxwell™s equations

Local maximum record level 1. In a magnetic tape,
maxima magnetic disk, or phonograph disc, the highest
amplitude of input signal that can be recorded
with an acceptable amount of distortion. 2. The
recording-head current or power that results in
third-harmonic distortion of three percent.
maximum signal level 1. In an amplitude-modu-
x lated signal, the peak power. 2. In an amplitude-
modulated facsimile or television system, the
amplitude that results in a black or white picture
(depending on whether the highest amplitude
produces black or white).
maximum undistorted power output Abbrevia-
tion, MUPO. The highest power that an active am-
plifying device will deliver before significant
maxima distortion occurs.
maximum usable frequency Abbreviation, MUF.
The highest frequency that can be used success-

intensity. 5. The study and solution of maximum, fully at a given time, between two specific geo-
minimum, and inflection points on the curve of a graphic locations, for communication via the

function. ionosphere.
maximal flatness For an amplifier or network, the maximum voltage 1. Abbreviation, Em, Emax, Vm,
condition in which peaks are not present in the or Vmax. The peak value reached by an alternat-
normal passband response. ing-current voltage half-cycle, or by a voltage
maximum Abbreviation, max. The highest value in pulse. 2. The highest value of voltage in a series
a range or set. Also see MAXIMA AND MINIMA of voltage measurements or calculations.
and PEAK. maximum wattage See MAXIMUM POWER.
maximum available gain Abbreviation, MAG. The maxterm form In mathematical calculations, the
amplification provided by a circuit or device factored form of a function, expressed as a prod-

whose input and output impedances are correctly uct of sums. For example, the maxterm form of
f(x) = x2 + 5x + 6 is f(x) = (x + 2) (x + 3).
matched to source and load.
maximum current 1. Symbol, Im or Imax. The high- maxwell Symbol, Mx. The cgs unit of magnetic
flux, equivalent to one line of flux or 10“8 weber.
est value reached by an alternating-current half-
cycle or by a pulse current. Also called PEAK Maxwell bridge A four-arm alternating-current
CURRENT. 2. The highest value of current in a bridge for measuring inductance against a stan-
series of current values. dard capacitance.
maximum power 1. Symbol, Pm or Pmax. The high- Maxwell™s equations A set of four equations devel-
est value of power that an equipment can be oped by James Clerk Maxwell in 1864 and 1873,
called upon to supply. 2. The highest value of describing vector quantities pertaining to points in
power in a series of measurements or calcula- space subjected to varying electric and magnetic
tions. forces. Through his classic presentation, Maxwell
maximum-power discharge current For a cell or
battery, the current at which the greatest amount
of power is delivered.
maximum power output See MAXIMUM POWER,
maximum power transfer The condition in which
the largest amount of power is delivered by a
source to a load.
maximum power transfer theorem Maximum
power is transferred from a generator to a load
when the impedance of the load equals the inter-
nal impedance of the generator. Compare COM-
maximum rating 1. The highest value of a quantity
(e.g., current, voltage, or power) that can safely be
used with a given device. 2. The highest value of a
quantity afforded by a given device (e.g., maximum
Maxwell bridge
capacitance of a variable capacitor).

Maxwell™s equations • measurand

predicted the existence of electromagnetic waves,
whose later discovery made radio possible.
Maxwell™s law Also called Maxwell™s rule. Every
part of an electric circuit is acted upon by a force
tending to move it in the direction that results in
the maximum magnetic flux being enclosed. RF output
maxwell-turn A unit of magnetic coupling (linkage)
equal to 1 maxwell per turn of wire in a coil linked
by magnetic flux. Also see MAXWELL.
mayday In radiotelephony, a word spoken as an
international distress signal equivalent to SOS in
radiotelegraphy. The word is the phonetic equiva-
Meacham oscillator
lent of the French m™aidez (help me).
MB Abbreviation of MIDBAND.
Mb Abbreviation of MEGABAR.
MBB Abbreviation of MAKE BEFORE BREAK. provided with a feedback circuit containing a
MBM Abbreviation of magnetic bubble memory. four-arm bridge, one arm of which is a quartz
MBO Abbreviation of MONOSTABLE BLOCKING crystal, and another, a tungsten-filament lamp
OSCILLATOR. acting as a nonlinear resistor. Also called bridge-
MBS Abbreviation of magnetron beam switching. stabilized oscillator.
mc 1. Symbol for MILLICURIE (mCi is preferred). mean 1. A general term meaning average. 2. See
Mc 1. Symbol for MEGACURIE (MCi is preferred). mean charge 1. In an object that is nonuniformly
2. Obsolete abbreviation of megacycle(s), a term charged, the average charge per unit distance,
superseded by MEGAHERTZ. area, or volume. 2. In a capacitor carrying a fluc-
MCG Abbreviation of MAGNETOCARDIOGRAM. tuating current, the average amount of charge
McLeod gauge An instrument for measuring gas held by the plates.
under low pressure. A measured volume of the mean free path 1. In acoustics, the average dis-
gas under test is first compressed (to a lower tance that sound waves travel before striking a
known volume) to a pressure more easily mea- barrier or reflecting surface. 2. The average dis-
sured via a mercury manometer and the applica- tance that sound waves travel between reflections
tion of Boyle™s law. (echoes) in a chamber. 3. In a gas tube, the aver-
MCM Abbreviation of MONTE CARLO METHOD. age of all the free paths of electrons at a specified
McProud test A simple test for checking the track- temperature.
ing efficiency of a phonograph pickup and arm for mean life 1. Symbol, L. The average life of a ra-
microgroove discs. dioactive substance [i.e., the time taken for 1/e
Mc/s Obsolete abbreviation of megacycle(s) per (e = base of natural logarithms) of the substance
second, a term superseded by MEGAHERTZ. to disintegrate]. 2. The time required for excess car-
MCS 1. Abbreviation of Master of Computer Sci- riers injected into a semiconductor to recombine
ence. 2. Abbreviation of missile control system. with carriers of opposite sign. Also called average
MCW Abbreviation of MODULATED CONTINUOUS life.
WAVE. mean proportional See GEOMETRIC MEAN.
Md Symbol for MENDELEVIUM. mean time before failure Abbreviation, MTBF.
MDAS Abbreviation of medical data acquisition sys- The average length of time that a component or
tem. system will perform before the first failure occurs.
m-derived filter A filter whose inductance (L) and It is generally specified in hours.
capacitance (C) values are derived by multiplying mean time between failures Abbreviation, MTBF.
those of a constant-k filter by a factor m between The average length of time that a component or
zero and 1. This factor is a function of the ratio system will perform before failure occurs”either
fÏ/fc, where fÏ is the frequency of infinite attenua- initially or after repair or replacement. It is gener-
tion, and fc is the cutoff frequency. This type of fil- ally specified in hours.
ter exhibits sharper response than the equivalent measured A quantity that is presented to an in-
constant-k filter. strument for measurement.
MDI Abbreviation of MAGNETIC DIRECTION INDI- measured service Any service in which charges
CATOR. are assessed per unit-time usage block. Online
M-display See M-SCAN. computer services are a common example. In
MDS Abbreviation of MINIMUM DISCERNIBLE some cases, other factors, such as distance, af-
SIGNAL. fect the cost per unit time; most long-distance
me Symbol for MASS OF ELECTRON AT REST. telephone services fall into this category.
Meacham oscillator A highly stable radio- measurand Any quantity that is measured with an
frequency oscillator consisting of an amplifier instrument.
438 measurement • medium-scan television

measurement 1. The process by which the magni- chanical television receiver. See, for example,
tude, extent, or duration of a parameter is found. NIPKOW DISK.
2. The value of a parameter, as obtained, accord- mechanical switch A switch actuated by moving
ing to 1. or sliding a lever, pressing a button, or otherwise
measurement error The difference between the applying mechanical pressure.
measured value of a quantity and its true value. mechanical time constant For a torque motor,
Also see NEGATIVE ERROR OF MEASUREMENT the ratio of moment of inertia to damping factor.
measurement range In a measuring device, the mechanical wave filter See ULTRASONIC FIL-
range within which the error is smaller than a TER, 1.
specified value. mechanics The branch of physics concerned with
mechanical analogs Familiar mechanical devices, forces and motion and the laws of gases and liq-
systems, or effects with which certain electrical uids. It is subdivided into kinematics and kinet-
counterparts can be compared for ease in teach- ics.
ing or understanding (e.g., inductance compared mechatronics Combination of the words mechan-
with mass, capacitance with elasticity, voltage ics and electronics, referring to the use of elec-
with pressure, and current with velocity). tromechanical devices (especially robots) in
mechanical axis In a quartz crystal, the axis per- manufacturing. The term was originally coined in
pendicular to the faces of the hexagon. Also see Japan.
Y-AXIS, 2. median 1. The middle value in a sequence of num-
mechanical bandspread Bandspread tuning ob- bers. For example, in the series: 1, 2, 3, 4, 5, 6, 7,
tained by reduction-ratio gearing of the tuning the median is 4. Compare ARITHMETIC MEAN
mechanism. Compare ELECTRICAL BAND- and GEOMETRIC MEAN. 2. In a statistical distri-
SPREAD. bution, the value s in the domain so that the area
mechanical bias 1. A steady pull applied by a under the curve for all values less than s is equal
spring to the armature of a relay to sensitize it by to the area under the curve for all values greater
decreasing the distance that the armature must than s.
move to close the contacts. 2. Bending of a relay medical electronics See ELECTROMEDICAL EN-
frame to position the armature closer to the mag- GINEERING.
net for the purpose defined in 1. medical robot 1. A robot used in a doctor™s office,
mechanical damping Damping action obtained or in a hospital to assist doctors and nurses.
entirely by mechanical devices (such as weights, There are various applications, some of which
dashpots, etc.). have provoked controversy (e.g., robotic surgical
mechanical equivalent of heat The amount of assistant). It generally performs simple, noncriti-
mechanical work required to produce a unit cal tasks. It has been suggested as a means of en-
quantity of heat. For example, 4.183 joules can tertaining hospital patients”especially children.
be converted into 1 calorie of heat. 2. See BIOMECHANISM.
mechanical equivalent of light The expression of medium In a computer system, that storage device
luminous energy in equivalent power units. In onto or into which data is recorded for input into
practical measurements, this is taken as the total memory (e.g., magnetic disk, magnetic tape, opti-
power output of a lamp minus the power ab- cal disk, etc.).
sorbed by a transparent jacket used to remove medium-frequency Abbreviation, MF. Pertaining
the infrared and ultraviolet rays. to frequencies in the range 300 kHz to 3 MHz,
mechanical filter See ULTRASONIC FILTER, 1. representing wavelengths from 1000 meters to
mechanical joint A union of electrical conductors 100 meters.
consisting exclusively of a junction or splice made medium of propagation The substance (or vac-
without brazing, soldering, or welding. uum) through which electromagnetic energy is
mechanical load An electromechanical device that transmitted (e.g., outer space, the atmosphere, or
uses the output of an electrical source. Such de- a dielectric material).
vices include actuators, brakes, clutches, meters, medium-scale integration A method of manufac-


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