. 23
( 42)


ment that consists of two gates as a unit. 3. To lattice filter A lattice network having reactance in
maintain a closed (energized) state in a pair of re- its arms that makes it a selective circuit.
lay contacts after initial energization from a sin- lattice network See LATTICE, 2.
gle electrical pulse. See LATCHING RELAY. lattice section See LATTICE, 2.
latching current In a thyristor, the minimum lattice structure See LATTICE, 1.
value of anode current (slightly higher than the lattice winding See UNIVERSAL WINDING.
holding current) that will sustain conduction im- laue diagram A pattern of spots on a photographic
mediately after switch-on. plate produced by the scattering of high energy
latching relay An electromechanical or fully elec- radiation as it falls on a thin crystal. This pattern
tronic relay that locks into whichever mode it is is used to determine the nature of the crystal
energized for (on or off). material.
launching • LC

law of natural decay See EXPONENTIAL DE-
law of natural growth See EXPONENTIAL IN-
Input law of normal distribution Gauss™ law of the fre-
quency distribution of a repetitive function, de-
scribing the probability of deviations from the
law of octals Chemical activity occurs between two
atoms lacking eight valence electrons, and con-
tinues until the requirement of eight electrons is
lattice filter
satisfied for all but the first orbit, where only two
electrons are required. Of interest in the study of
launching The energy transference from a cable semiconductors.
into a waveguide. law of radiation See QUANTUM THEORY.
lavalier microphone A small microphone that can law of reflection For a ray of energy striking a
be hung from the user™s neck on a cord or chain. smooth reflective surface, the angle of reflection
law 1. A general, verifiable statement that describes is equal to the angle of incidence, with respect to
the behavior of entities or the relationships be- a plane tangent to the surface at the point of inci-
tween phenomena or concepts. The product of in- dence.
ductive reasoning that follows many observations Lawrence accelerator See CYCLOTRON.
and controlled experiments (e.g., first law of lawrencium Symbol, Lr (occasionally Lw). A short-
thermodynamics, inverse-square law, Kirchhoff™s lived radioactive element produced artificially
laws, and Ohm™s law. 2. The nature of the change from californium. Atomic number, 103. Atomic
of a dependent variable, particularly as depicted weight, about 260.
by a response curve (e.g., square law). lay See DIRECTION OF LAY.
LAWEB Civilian weather bulletins issued every six layer 1. A complete coil winding consisting of turns
hours from ship and shore positions along the laid side by side (not on top of each other). 2. In a
Great Lakes during the sailing season. semiconductor device, a region having unique
lawn mower 1. A facsimile term for a helix record- electrical properties (e.g., n layer). 3. A region
ing mechanism. 2. A radar receiver preamplifier. of the ionosphere. See IONOSPHERIC LAYERS.
law of a curve See LAW, 2. 4. The tape on a reel or in a cassette, encompass-
law of averages In probability and statistics, a ing one complete turn (rotation). 5. In general, a
principle stating that for a large sampling of single stratum of a stratified medium.
events, the numerical probability value will be layer-to-layer transfer In a roll of magnetic tape,
more closely approached than when the sampling unwanted transfer of data between adjacent
is small. Compare LAW OF LARGE NUMBERS. turns on the reel. If severe, this transfer can
law of charges Different electric charges attract cause drop-in or drop-out in a computer. In audio
each other, and similar charges repel each other. applications, it can sometimes be heard as a de-
law of electric charges See LAW OF CHARGES. layed echo or a faint sound occurring just prior to
law of electromagnetic induction See LENZ™S the actual recorded sound.
LAW. layer winding A coil winding in which the turns
law of electrostatic attraction See COULOMB™S are arranged in two or more concentric layers.
LAWS. layerwound coil An inductor wound in layers, one
law of electrostatic repulsion See COULOMB™S on top of the other. Also see LAYER, 1. Compare
law of first wavefront In acoustics, a rule stating layout The arrangement of components on a chas-
that the perceived direction from which a sound sis, printed circuit board, or panel.
arrives is determined by the first wavefront that lazy-H antenna An antenna consisting of two ver-
reaches the listener™s ears. tically stacked collinear elements, producing both
law of induction See FARADAY™S LAW. horizontal and vertical directivity.
law of inverse squares See INVERSE-SQUARE Lb Abbreviation of LAMBERT; also, L (preferred).
LAW. lb Abbreviation of POUND.
law of large numbers In probability and statistics, L band A radio-frequency band extending from 390
a principle stating that with a large sample, the MHz to 1.55 GHz. For subdivisions of this band,
sample average will approximate the population see LC BAND, LF BAND, LK BAND, LL BAND, LP
average. It is often erroneously called LAW OF BAND, LS BAND, LT BAND, LX BAND, LY BAND,
law of magnetism Different magnetic poles attract LC 1. Abbreviation of LIQUID CRYSTAL; also ab-
each other, and similar magnetic poles repel each breviated lix. 2. Abbreviation of INDUCTANCE-
other. CAPACITANCE. 3. Symbol for LC CONSTANT.
402 L carrier • lead frame

L carrier In a telephone system, a carrier having a lead“acid battery A set of two or more lead“acid
frequency between approximately 68 kHz and 10 cells connected in series, usually housed in a
MHz. It can be used in wire-transmission or radio common enclosure. Some batteries of this type,
links. notably automotive batteries, are made from sets
LC band A section of the L BAND extending from of lead“acid cells having a free-flowing liquid acid.
465 MHz to 510 MHz. Other cells have a semisolid “paste” electrolyte.
LC bridge See INDUCTANCE-CAPACITANCE These batteries are popular in consumer elec-
BRIDGE. tronic devices that require a moderate amount of
LC constant Abbreviation, LC. The product of the current. They are also used in uninterruptible
inductance and capacitance required for reso- power supplies (UPSs) for personal computers.
nance at a given frequency. See LEAD“ACID CELL.
LCD Abbreviation of LIQUID-CRYSTAL DISPLAY. lead“acid cell A rechargeable electrochemical cell
LC filter See INDUCTANCE-CAPACITANCE FIL- having an electrolyte of sulfuric acid. The elec-
TER. trodes are lead (negative) and lead dioxide (posi-
L circuit See L NETWORK. tive). Produces about 1.5 volts under no-load
LC meter See INDUCTANCE-CAPACITANCE ME- conditions when fully charged. A large cell of this
TER. type can store several tens of ampere-hours.
LCR See INDUCTANCE-CAPACITANCE-RESIS- Smaller units have less capacity but more versa-
TANCE. tility. Their main advantage is reasonable cost,
LC ratio In a tuned circuit, the ratio of inductance considering that they can be charged and dis-
to capacitance. charged many times.
Filler cap and vent
Sealing compound
L display Also called L scan. A radar display in
which the target appears as two horizontal
traces, one extending from a vertical timebase to Negative
the right, the other to the left. plate
lead Pronunciation, leed. 1. A conductor (usually
a wire) leading to or emerging from a terminal or
electrode. 2. In computations relating phase, the Slotted rubber
extent to which one quantity precedes another
(e.g., current leads voltage by 90 degrees in a
pure capacitance). Compare LAG.
lead Pronunciation, led. Symbol, Pb. A heavy
metallic element. Atomic number, 82. Atomic Rubber
weight, 207.2. It can be used as a shield against Bottom
atomic radiation, and has various applications in
electronics (e.g., as electrodes in batteries and as
a component of solder). See LEAD-ACID BAT-
Bottom of
positive plate

Supports Sediment spaces

lead-acid cell

lead cell 1. A lead-acid cell. 2. A lead-sulfide pho-
tocell; see LEAD SULFIDE, 1.
lead dress See DRESS.
leader 1. The blank section at the beginning of a
magnetic tape. It is usually made of plastic. 2. A
record, preceding a group of records, that identi-
fies the group and provides other data pertinent
to the group. 3. In a lightning stroke, the initial
movement of electrons or positive ions, creating
the ionized path that allows discharge.
lead frame The metal frame holding the leads
of a circuit package (DIP) in place before
lead-in • least-significant digit

lead-in The wire connecting an antenna to a re- leakage 1. The small current that flows through an
ceiver or transmitter. electrical insulator. 2. The electromagnetic field
leading current Current that precedes voltage in that is radiated or received by a feed line that
time. Also see LEAD. should theoretically have 100-percent shielding.
leading edge The rising edge of a pulse; compare leakage current The zero-signal current flowing
TRAILING EDGE. across a reverse-biased semiconductor junction.
leading ghost A twin television image to the left of leakage flux Collectively, magnetic lines of flux
the original on the screen. around a transformer that do not link the pri-
leading load A load in which current leads voltage mary and secondary coils.
(i.e., a capacitive load). leakage inductance Self-inductance caused by
lead-in groove Around the outer edge of a phono- LEAKAGE FLUX. Leakage inductance is effec-
graph record, a blank spiral groove that leads the tively in series with the primary or secondary
stylus into the first groove of the recording. Com- winding of a transformer.
pare LEAD-OUT GROOVE. leakage resistance 1. In an imperfect insulator,
leading whites In a television picture, an abnor- the ohmic resistance, calculated by dividing the
mal condition in which the leading (left) edge of a voltage across the insulator by the current flow-
black object has a white border. ing through the insulator. 2. The quotient of
leading-zero suppression In a digital meter, the voltage and current in a reverse-biased semi-
blanking out of all zeros to the left of the decimal conductor junction.
point. leakage radiation Radiation from parts of a system,
lead-in spiral See LEAD-IN GROOVE. as compared with that from the true radiator.
lead-in tube A tube of insulating material, such as leakage reactance Inductive reactance caused by
plastic or ceramic, used to conduct an antenna leakage inductance in the primary or secondary
lead-in through a wall. circuit of a transformer.
lead-in wire 1. A single wire, used as a feed line for leakance The conductance of an insulating mate-
a shortwave receiving antenna. 2. The feed line rial, measured in siemens. It is equal to the recip-
for a television receiving antenna. 3. A feed line rocal of the leakage resistance in ohms.
for a transmitting antenna. leaky 1. Descriptive of a capacitor in which the di-
lead network A phase-shift circuit containing series electric material is not a perfect insulator. 2. De-
capacitance and shunt resistance; it produces a scriptive of imperfect shielding in a coaxial
leading phase shift. Compare LAG NETWORK. transmission line. 3. Descriptive of a waveguide
lead-out groove Around the inner edge of a phono- with imperfect shielding.
graph record, a blank spiral groove leading into leaky dielectric See LEAKY INSULATOR.
the eccentric or locked groove. leaky insulator An insulator that conducts signifi-
lead-over groove On a phonograph record con- cant current at a specified (test) voltage.
taining several recorded tracks, a blank groove leaky waveguide A waveguide that has imperfect
that conducts the stylus from the end of one shielding, allowing some electromagnetic field to
recording to the beginning of the next. escape.
lead screw 1. A threaded rod that guides the cutter leapfrogging In radar, a phasing process that
across the surface of a disc during its recording. eliminates false echoes resulting from the signals
2. In facsimile transmission, a threaded shaft of other radar sets.
that moves the drum or scanning mechanism leapfrog test A test performed on different loca-
lengthwise. tions by a computer program in memory; it moves
lead sulfate Formula, PbSO4. An insulating com- to another memory area to continue tests on
pound formed in a LEAD-ACID CELL by the other locations.
chemical action between the lead in the plates learning The ability of an artificially intelligent ma-
and the sulfuric-acid electrolyte. If the sulfate is chine to improve or expand its knowledge with
not broken down during charging of the cell, it time. This can occur as a result of accumulation
will eventually ruin the cell. of information; it can also occur in systems that
lead sulfide Formula, PbS. A compound of lead track their errors to avoid repeating them.
and sulfur used as the light-sensitive material in leased line A communications circuit reserved ex-
some photoconductive cells. clusively for a specific user.
lead zirconate titanate A synthetic piezoelectric least-significant bit Abbreviation, LSB. The digit
material. with the lowest place value in a binary number.
leaf electroscope An electroscope using a pair of least-significant character Abbreviation, LSC. In
gold leaves or a single gold leaf and a solid strip of positional notation, the extreme right-hand char-
metal. acter in a group of significant characters. See
leak 1. The loss of energy through a stray path not POSITIONAL NOTATION.
intended for conduction. 2. A point from which least-significant digit Abbreviation, LSD. The
energy is lost through a stray path not intended digit in a number that is at the extreme right (i.e.,
for conduction. the one having the lowest place value).
404 least upper bound • level-0 security

least upper bound The smallest value of a param- item needs fewer positions than have been pro-
eter that can be obtained without changing some vided.
characteristic of a circuit, program or system. left shift A shift operation in which the digits of a
Lecher frame A sturdy assemblage of LECHER word are displaced to the left; the effect is multi-
WIRES. plication in an arithmetic shift.
leg 1. Any one of the distinct branches of a circuit
or network; also called ARM or BRANCH. 2. In a
Diode computer program, a path in a routine or sub-
Standoff Short-circuiting L electron In certain atoms, an electron whose or-
insulator bit is outside of, and nearest to, the orbit of the K
Lenard rays See CATHODE RAYS.
length 1. The number of bits or characters in a
record, word, or other data unit. 2. The end-
to-end dimension of a device, circuit, line, etc.
Scale 3. The start-to-finish duration of a time interval.
length to fault In cable or line measurements from
the home station, the distance (i.e., the cable or
Lecher frame
line length) to the point at which a fault, such as
a short circuit or ground, is located.
lens 1. A usually circular piece of transparent ma-
Lecher lines See LECHER WIRES.
terial with one or both surfaces curved in cross
Lecher oscillator A self-excited radio-frequency
section, used (through its refractive properties) to
oscillator using Lecher wires in place of an induc-
focus or spread rays that pass through it. Lenses
tance-capacitance (LC) tank circuit. Also see
for visible light must be transparent, but those
for other radiation, such as radio waves, need not
Lecher wires A circuit segment consisting of two
transmit light. Also see ANTENNA LENS. 2. In a
parallel wires or rods joined by a coupling loop on
cathode-ray tube, one or more high-voltage elec-
one end, the other end being open. A short-
trodes for focusing an electron beam to a fine
circuiting bar is moved along the wires to vary the
point on the screen.
effective length of the circuit. Radio-frequency en-
lens antenna See ANTENNA LENS.
ergy is inductively coupled into the system
lens disk A NIPKOW DISK having a lens in each
through the loop, and the bar is slid along to var-
ious response points, as indicated by a meter or
lens speed The light-transmitting ability of a lens,
lamp coupled to the wires. The frequency can be
given as an f-stop number: the lens™ focal length
determined by measuring the distance between
divided by its diameter.
adjacent response points. It is used at very-high
lens turret A multiple-lens mount on a camera
frequencies (VHF), ultra-high frequencies (UHF),
that can be rotated for quick lens interchange.
and microwave frequencies. Also called Lecher
frame and Lecher lines.
LEO satellite system A set of several dozen low
Leclanche cell See DRY CELL, 1.
earth orbit (LEO) satellites in polar orbits spaced
strategically around the globe such that, for any
LED phototransistor isolator An optoelectronic
point on the earth, there is always at least one
isolator in which the light source is a light-
satellite in range. The satellites can relay mes-
emitting diode and the light-sensitive component
sages throughout the fleet. Any two points on the
is a phototransistor.
surface are always able to make contact through
LEDE Abbreviation for LIVE END/DEAD END.
the satellites.
Lepel discharger See QUENCHED SPARK GAP.
left-hand lay See DIRECTION OF LAY.
letter-identification word See PHONETIC ALPHA-
left-hand motor rule See FLEMING™S LEFT-HAND
letters patent See PATENT.
left-hand polarized wave See COUNTERCLOCK-
letters shift In a text communications terminal, a
control character that causes all of the following
left-hand taper Potentiometer or rheostat taper in
characters to occur in the lower case. This can be
which most of the resistance is in the counter-
an automatic or a manual control character.
clockwise half of rotation as viewed from the
let-through current The current conducted by a
front. Compare RIGHT-HAND TAPER.
circuit breaker during a short-circuit.
left justified An item of data that occupies consec-
level-0 security In communications, the complete
utive locations in storage, starting at the left-
lack of security measures. Anyone can listen in
hand end of its area; empty locations might
on a conversation at any time, provided they are
appear consecutively at the right-hand end if the
level-0 security • life

willing to spend the money and/or time to obtain In modern form, it is a glass jar covered inside
the necessary equipment. Examples are amateur and out with metal foil and has a rod topped by a
(“ham”) radio and Citizens™ Band (CB) voice com- metal ball that touches the inner foil. It is still
munications. used occasionally in classrooms for demonstrat-
level-1 security Also called wire-equivalent secu- ing static electricity. The Leyden jar was co-
rity. In communications, the implementation of invented by van Musschenbroek and invented
security measures such that the circuit is pro- independently by E. G. von Kleist of Pomerania,
tected to the extent of a typical hard-wired link. among others.
The encryption is anticipated to be unbreakable
for at least 12 months, and preferably for
24 months or more. The technology is updated
electrode Insulating
at least every 12 months, and preferably every
metal cover
6 months. plate
level-2 security Also called commercial-level secu-
rity. In communications, the implementation of
security measures such that the circuit is
deemed safe for ordinary commercial transac-
tions. The encryption is anticipated to be of such
a nature that engineers believe it would take a
hacker at least 10 years, and preferably 20 years Outer metal
or more, to break the cipher. The technology plate
should be updated at least every 10 years, but
preferably every 3 to 5 years, and more often if
Leyden jar
level-3 security Also called mil-spec security. In
communications, the implementation of security Leyden phial See LEYDEN JAR.
involving the most sophisticated forms of encryp- Leyden vial See LEYDEN JAR.
tion and personnel restriction that a government LF Abbreviation of LOW FREQUENCY.
can muster. LF band A section of the L BAND extending from
level 1. The amplitude at which a device is func- 1.35 to 1.45 GHz.
tioning or at which a phenomenon occurs (e.g., L fitting See ELL.
collector-current level, or received signal level). LHD Abbreviation of LOAD/HAUL/DUMP.
2. The minimum amplitude at which a pheno- Li Symbol for LITHIUM.
menon occurs; also called threshold amplitude. 3. librarian program A computer program controlling
A functional plateau or echelon. a LIBRARY.
level clipper See CLIPPER. library In digital-computer and data-processing
level compensator 1. An automatic gain control operations, the permanent storage of data or in-
(AGC) that effectively reduces amplitude varia- structions. Also called permanent mass storage.
tions in a received signal. 2. An automatic gain libration fading In earth-moon-earth (EME) com-
control in telegraph receiving equipment. munications, also known as moonbounce, rapid
level control 1. The adjustment of amplitude or and deep fading, accompanied by phase modula-
threshold. 2. A potentiometer or other variable tion, that takes place because the moon does not
component for adjusting the amplitude or thresh- always show the earth exactly the same portion of
old of a quantity. its surface. The moon “wobbles” slightly back and
level indicator See VOLUME INDICATOR. forth on its axis. This causes changes in the rela-
level translator Any circuit or device that alters tive phases of signals reflected from the topo-
the voltage levels of input signals. An example is graphic features (mountains, in particular) on the
a converter that changes positive-logic signals to lunar surface.
negative-logic signals. licrystal An acronym from liquid and crystal. See
level-triggered flip-flop A flip-flop that responds LIQUID CRYSTAL.
to voltage level, rather than to the frequency of an lidar See LIGHT DETECTION AND RANGING.
input signal. lie detector See POLYGRAPH.
lever switch 1. A switch designed for rapid making life 1. The duration of useful service (or of opera-
and breaking of a circuit. 2. A radiotelegraph key. tion before failure) of electronic equipment. 2. For
Lewis antenna A form of antenna used at ultra- a non-rechargeable cell or battery, the length of
high and microwave frequencies. It resembles a time it will last in a given application before it
horn antenna. must be discarded and replaced. 3. In robotics
Leyden bottle See LEYDEN JAR. and artificial intelligence (AI), a general term that
Leyden jar [Leyden, Holland (also Leiden), site of refers to qualitative similarities between ma-
the invention in 1745 by Peiter van Musschen- chines and animate creatures, including human
broek, 1692“1761.] The first practical capacitor. beings.
406 life test • light-induced electricity

life test An assessment of the life of electronic
equipment”either by means of full-time test
runs or accelerated time tests.
lifter A device in a magnetic tape recorder that Terminal
removes the tape from the recording and play-
back heads under fast-forward and rewind con-
light Visible electromagnetic radiation occurring in
the wavelength band of about 750 nanometers
(red light) to 390 nanometers (violet light). In-
cluded sometimes in the category of light are in-
frared and ultraviolet rays.
light-activated silicon-controlled rectifier Ab-
breviation, LASCR. A silicon-controlled rectifier light
that functions both as a photosensor and a heavy- beam
duty bistable electronic switch, allowing high cur-
rents to be switched by means of a light beam.

light-activated silicon-controlled switch Abbre-
viation, LASCS. A pnpn device that acts simulta-

neously as photocell and electronic switch.
light adaption 1. The process whereby the eye ad- Telescope
justs itself to an increase or decrease in illumina- (for focusing light beam)
tion. 2. Similar action in photoelectric devices.
3. The length of time required for the eye to adjust
itself to an increase or decrease in illumination.
light amplifier A solid-state amplifier using an in- Modem Terminal
put electroluminescent cell and an output photo-
cell, or some similar pair of components. The

device is essentially an optoelectronic coupler
with gain.
light-beam communication A system of commu-
nication in which a beam of light between trans-
light-beam communication
mitting and receiving stations is modulated or
interrupted to convey intelligence. A laser is com-
monly used because it has minimal beam diver-
gence, allowing maximum communication range. light detection and ranging Acronym, lidar. A
light-beam meter An electric meter using a navigation and surveillance system in which laser
LIGHT-BEAM POINTER. light scans in a manner similar to that of RADAR.
light-beam pointer A slender beam of light that re- light dimmer See DIMMER.
places the pointer in a moving-coil meter. The lighted pushbutton See LIGHTED SWITCH.
light comes from a small incandescent lamp and lighted switch A pushbutton switch containing a
is reflected by a mirror attached to the coil; when pilot light that glows to show when the switch is
the coil moves, a spot of light moves over the scale on. Also called illuminated switch.
of the meter. light-emitting diode Abbreviation, LED. A semi-
light-beam receiver The receiver in a LIGHT- conductor device that emits visible light when for-
BEAM COMMUNICATION system. ward biased. Also see LASER DIODE.
light-beam recorder A graphic recorder using a light-emitting film A thin phosphor film that
light-beam pointer. In this device, a small spot of becomes luminescent when a high-frequency
light traces a pattern on moving photographic voltage is applied across its surface. Also see
film, which is subsequently developed to produce ELECTROLUMINESCENCE and ELECTROLUMI-
a permanent record. NESCENT CELL.
light-beam transmitter The transmitter in a light flasher An electronic circuit or simple auto-
LIGHT-BEAM COMMUNICATION system. matic flasher switch for flashing a lamp at regular
light cable A cable, consisting of numerous thin intervals.
optical fibers, through which light can be trans- light flicker See LOAD FLICKER.
mitted for communication or control purposes. light flux See LUMINOUS FLUX.
See, for example, LIGHT-WAVE TELEPHONY. light hood See HOOD.
light chopper A device that modulates a light light-induced electricity See PHOTOELECTRIC-
beam by interrupting it repetitively. ITY.

light load • light sensor

light load A load that is a fraction of the usual Lightning
value for a given application. That is, its resis-
tance or impedance is several times higher than
normal. Cone of
45° 45°
light meter An electronic instrument for measur- protection
ing the intensity of light. It generally consists of
a photodiode, a battery, and a direct-current mi-
croammeter connected in series. A direct-
current amplifier can be used to increase the
light microsecond A unit of electrical distance;
the distance that light, or any electromagnetic
disturbance, travels in free space in 1 microsec-
ond. Approximately equal to 300 meters.
lightning rod
light modulation Variation of the instantaneous
brightness of a visible light beam in synchroniza-
tion with the instantaneous amplitude of a mod- lightning stroke The discharge that occurs with
ulating signal. Also see LIGHT MODULATOR. lightning. The peak current is typically several
light modulator A device with which a beam of tens of thousands of amperes, but in some cases
light can be modulated by an electrical signal. can exceed 1,000,000 amperes. A stroke can con-
light negative Pertaining to negative photocon- sist of one discharge or several individual dis-
ductivity, the decrease in conductivity of a photo- charges in rapid succession.
sensitive material under illumination. Compare lightning switch See GROUND SWITCH.
LIGHT POSITIVE. light-operated relay See PHOTOELECTRIC RE-
lightning The discharge that occurs between posi- LAY.
tive and negative poles in the atmosphere. Com- light-operated switch A PHOTOELECTRIC RE-
mon in and near areas where heavy rainfall is LAY, or a switch operated by such a relay.
occurring. It also can occur in snow storms, in light pen A probe containing a tiny photosensor in
sand storms, and over erupting volcanoes. Gen- its tip. The tip of the light pen is touched to the
erally, the negative pole is in a cloud and the pos- screen of a cathode-ray tube to sense the beam
itive pole is at the surface of the earth, resulting when it passes the spot of contact. It is used as
in a flow of electrons from cloud to ground. Some an input device in some computers and termi-
lightning occurs as a flow of electrons from nals.
ground to cloud, or between two clouds. Such light pipe 1. An OPTICAL FIBER. 2. A cable con-
discharges sometimes attain current levels of sisting of numerous optical fibers in a bundle.
more than 1,000,000 amperes. See FIBEROPTICS, 1.
lightning arrester A device that bypasses high- light positive Pertaining to positive photoconduc-
voltage pulses from most nearby lightning dis- tivity, when the conductivity of a photosensitive
charges to the earth, helping to protect electronic material increases under illumination. Compare
equipment connected to an outdoor antenna or LIGHT NEGATIVE.
power line. Is not a total guarantee of protection, light quantum See PHOTON.
however. light ray A thin beam of light. Theoretically, a ray
lightning conductor 1. A system for protecting emerges from a point source (i.e., it has no width).
buildings from lightning strikes. A common sys- light receiver See LIGHT-BEAM RECEIVER.
tem includes a lightning rod, heavy conductor, light relay A photoelectric device that operates a
and ground rod. The ground rod is placed at least relay, according to fluctuations in the intensity of
six feet from the base of a building and is at least a light beam.
eight feet long. 2. The conductor between the light-sensitive cathode Also called photocathode.
lightning rod and ground rod in a system, as de- A cathode that emits electrons when exposed to
fined in 1. light.
lightning detector See KERAUNOGRAPH and light-sensitive diode A semiconductor diode us-
KERAUNOPHONE. able as a photoconductive cell. Such diodes are
lightning rod A protective device mounted on the available as both junction and point-contact
outside of structures, consisting of a pointed, types.
grounded metal rod that will conduct a lightning light-sensitive material A photoconductive or
discharge to earth. photoemissive substance.
lightning strike A direct hit of an object by a light- light-sensitive resistor See PHOTOCONDUCTIVE
ning stroke. It usually causes extensive damage CELL.
to electrical and electronic equipment through light sensor 1. A light-sensitive device, such as
which the discharge passes. a photocell, photodiode, phototransistor, or
408 light sensor • linear algebra

phototube. 2. A light-sensitive substance, such
as cesium, selenium, silicon, cadmium selenide,
or lead sulfide.
light source Any generator of light. Under some
conditions, the source is regarded as a point.

Peak amplitude
light spectrum See ELECTROMAGNETIC THE-

light-spot scanner Also called flying-spot scanner.
A television camera using (as a source of illumi-
nation) a spot of light that scans what is to be
light transmitter See LIGHT-BEAM TRANSMIT-
light valve 1. An electromechanical device for
varying the intensity of light passing through its
adjustable aperture. 2. See KERR CELL.
light-wave telephony Telephone communication
by means of modulated-light transmission, usu- limiting error The anticipated maximum value of
ally through an OPTICAL FIBER. the absolute error in a computation.
light-year Abbreviation, lt-yr. Pertaining to astron- limiting resistor See CURRENT-LIMITING RESIS-
omy, a unit of distance equal to the distance trav- TOR.
eled by light in one year in a vacuum: 9.460 55 — limiting resolution As a measure of video image
1015 meters (5.878 — 1012 miles). resolution, the maximum number of lines for pic-
likelihood In probability and statistics, the chance ture height that can be discriminated on a test
that an event will occur or that an outcome will chart.
be realized. Also see PROBABILITY, 1, 2. limit switch A switch that is actuated when a
lim Abbreviation of LIMIT. monitored quantity (e.g., current, voltage, or illu-
Lima Pronunciation, LEE-ma. Phonetic alphabet mination) reaches the limit of its range.
word for the letter L. line 1. A wire, cable, or waveguide, along which
limen A unit that has been proposed as the mini- electrical or electromagnetic energy travels from
mum audible change in frequency that can be de- one defined place to another. 2. One lengthwise
tected by at least half of a group of listeners. path in which a force, such as electricity or mag-
limit 1. The lowest or highest frequency in a band. netism, is evidenced. Such a line of flux has theo-
2. In mathematics, a fixed value that a variable retically zero width.
approaches. 3. The upper and lower extremes in line advance 1. The physical separation between
any performance range or value range. the centers of adjacent scanning lines in a televi-
limit bridge A bridge used to check a component sion system. 2. Line feed in a text data transmis-
(e.g., resistance, capacitance, or inductance) in sion system.
terms of the tolerance limits, rather than the line amplifier An amplifier in a telephone line or
nominal (named) value, of that component. Also similar channel, or one feeding such a line from
see BRIDGE, 2. the input end.
limited integrator A circuit that integrates two in- linear 1. In a straight line. 2. In the manner of a
put signals until the corresponding output signal straight line. Thus, linear response is indicated
exceeds a certain limit. when one quantity varies directly with another;
limited stability A characteristic of a circuit or the graph of this response is a straight line (i.e.,
system, allowing proper operation only if the in- one of constant slope). 3. The characteristic of a
put signal and applied voltages are within certain signal that is a replica of another (e.g., an ampli-
maximum and minimum limits. fier output signal of the same waveform as that of
limiter A device or circuit whose output-signal am- the input signal).
plitude remains at some predetermined level, de- linear absorption coefficient A number express-
spite wide variations in input-signal amplitude. ing the extent to which the intensity of an X-ray
limiting The restriction of the maximum peak am- beam is reduced per centimeter of the material
plitude of a signal to a designated level. through which it passes.
limiting amplifier An amplifier that automatically linear accelerator A device in which subatomic
holds the output-signal level to a prescribed value. particles are accelerated in a straight line
limiting current In electrolysis, the highest cur- through a long tube. This action is in contrast
rent that conducts under certain conditions of with that occurring in a circular accelerator, such
ion concentration. This current depends on the as a CYCLOTRON.
electrolyte material, the concentration of the elec- linear algebra A branch of mathematics that deals
trolyte in solution, the electrode substance, and with the solving of linear equations or sets of lin-
the size of the electrolytic cell. ear equations.
linear amplifier • linear scale

linear amplifier 1. An amplifier for which a linear amplification, oscillation, nondigital regulation,
relationship exists between input and output pa- analog instrumentation, and similar applica-
rameters (e.g., a high-fidelity audio amplifier). tions). Compare DIGITAL INTEGRATED CIRCUIT.
2. A class-AB radio-frequency power amplifier that linearity 1. The degree to which performance or
does not distort the envelope of an amplitude- response approaches the condition of being lin-
modulated (AM) or single-sideband (SSB) signal. ear, expressed in percent or parts per million.
It is commonly used by amateur radio operators. Also see LINEAR AMPLIFIER, 1; LINEAR CIR-
linear array A directional antenna having equally CUIT, 1, 2; LINEAR OSCILLATOR, 1; LINEAR RE-
spaced, in-line elements. SPONSE, 1, 2, 3; and LINEAR TAPER. 2. In a
linear circuit 1. A circuit whose output is a faith- cathode-ray-tube image, absence of compression
ful reproduction of the input. See LINEAR AMPLI- or stretching of any portion of the image; that is,
FIER, 1 and LINEAR DETECTOR. 2. A circuit an undistorted reproduction.
whose performance is linear. See LINEAR RE- linearity control In a cathode-ray-tube display,
SPONSE, 1. the potentiometer used to correct image linearity.
linear decrement In a damped wave, a constant See LINEARITY, 2.
decrease in amplitude with time, as opposed to a linearity error 1. The difference between a theo-
decrease that is a logarithmic or otherwise non- retically linear function and the actual function,
linear function of time. Compare DECREMENT. as observed under experimental conditions.
linear detector A detector whose output/input re- 2. The degree of nonlinearity in an amplifier that
lationship is linear. Also see LINEAR, 2, 3; LIN- is supposed to be linear.
EAR CIRCUIT, 1; and LINEAR RESPONSE, 1, 2, linear modulation 1. Modulation in which the
3. instantaneous amplitude of the input signal is
linear differential transformer A device that con- directly proportional to the instantaneous ampli-
verts the physical position of an object into an tude of the output signal. 2. Modulation in which
output voltage or current. The voltage or current the instantaneous amplitude of the input signal
is directly proportional to the displacement. is inversely proportional to the instantaneous
linear distortion Amplitude distortion in which amplitude of the output signal. 3. Modulation in
the output and input signal envelopes are dispro- which the instantaneous amplitude of the input
portionate (in the absence of spurious frequen- signal is directly proportional to the frequency or
cies). phase deviation of the output signal.
linear equation See FIRST-DEGREE EQUATION. linear motor A motor in which the stator and rotor
linear function 1. In Cartesian two-space, a func- are parallel and straight.
tion of the form y = mx + b, where the coordinates linear oscillator 1. An oscillator whose alternat-
are (x,y), the slope is m (any real number) and b is ing-current output amplitude varies linearly with
the point on the y axis at which the graph crosses its direct-current input. 2. A line-type oscillator.
the axis. 2. Any function in any number of di- linear programming A method of determining the
mensions whose graph appears as a straight line optimum value for a certain set of linear equa-
in the Cartesian system of coordinates. tions. Generally, this is done by finding the point
on a plane in space closest to some point not on
y the plane.
linear quantizing A method of quantizing in which
all of the intervals are of equal size or duration.
An example is a linear analog-to-digital converter
linear reflex detector See INFINITE-IMPEDANCE
linear response 1. A response in which the value
x of the dependent variable is equal or directly pro-
portional to the value of the independent variable.
Thus, the graph of the response function is a
straight line over the range of normal operating
and SQUARE-LAW RESPONSE. 2. A type of re-
sponse in which a quantity (such as current)
varies directly with another quantity (such as
voltage). Compare LOGARITHMIC RESPONSE, 2.
linear function 3. Low-distortion response. Also see HIGH FI-
linear scale A scale in which all of the divisions
represent the same differential and are equally
linear integrated circuit An integrated circuit de-
spaced. On a linear scale, a given difference
signed for analog operations (such as signal
410 linear scale • line filter

10 line balance The degree of electrical similarity be-
9 tween transmission line conductors, or between a
9 8
conductor and ground.
8 line-balance converter A device used to isolate
the outer conductor at the end of a coaxial line
from ground.
6 4 line characteristic distortion Fluctuations in the
duration of received signal impulses in text data
Linear Nonlinear
communications, caused by changing current
transitions in the wire circuit.
line circuit The telephone system relay equipment
associated with stations connected to a switch-
2 board.
line code A code between the digits in processing
equipment and the pulses representing the digits
0 in a line transmission.
line conditioning In data communications, the
linear scale modification of private or leased lines by adding
compensating reactances to reduce amplitude
variations or phase delays over a band of fre-
always has the same physical length, no matter quencies.
where on the scale it appears. For example, the line contact stylus A needle used to reproduce
interval between 3 and 4 on a linear scale is the stereo high-fidelity sound from vinyl discs. It has
same as any interval between x and x + 1, where a characteristic oblate ellipsoidal shape.
x is any real value on the scale. line coordinate A symbol identifying a specific row
linear sweep In a television or oscilloscope circuit, of cells in a matrix; a specific cell can be located
the scanning of the electron beam across the with an additional column coordinate.
screen at a constant speed. Also see LINEAR, 1; line cord A flexible two- or three-wire insulated ca-
LINEAR RESPONSE, 1; and LINEARITY, 2. ble connecting equipment to the power line by
linear taper In a potentiometer or rheostat, resis- means of a plug that mates to a standard electri-
tance variation that is directly proportional to cal outlet.
shaft rotation. Thus, half the total resistance cor- line current 1. Current flowing from a power line
responds to movement of the shaft over half the into equipment. 2. Current flowing in a transmis-
arc of full rotation. Compare LOG TAPER. Also
sion line. 3. Current flowing into a parallel-
see TAPER.
resonant circuit.
linear time base For an oscilloscope, the base pro-
line diffuser A circuit that creates minor vertical
vided by sweeping the electron beam horizontally
oscillations of the spot on a television screen,
at a uniform rate. Also see LINEAR SWEEP.
making the individual scanning lines less notice-
linear track On a video tape, the track that con-
tains audio information that accompanies the
line driver An integrated circuit capable of trans-
video data. It was so named because it is a single,
mitting logic signals through long lines.
straight track, in contrast to the video tracks,
line drop The voltage drop along a line supplying
which are angled.
power to a device.
linear tracking In a turntable system, a design
line equalizer See EQUALIZER.
scheme in which the lateral movement of the sty-
line fault A discontinuity in a transmission line,
lus, as the disc is played, occurs in a straight line,
resulting in signal loss at the receiving end of a
rather than in an arc.
linear transformer A radio-frequency transformer
line feed In a text data transmission system, the
consisting of a section of transmission line.
movement of the paper, platen, or cursor to allow
linear variable differential transformer Abbrevi-
for printing or displaying an additional line of
ation, LVDT. A differential transformer exhibiting
linear response. Also see LINEAR RESPONSE, 1,
line filter 1. A circuit that can be inserted in the
utility power cord of an appliance, device, or sys-
tem for transient suppression and the minimiza-
tion of electromagnetic interference (EMI). The
Coupling link
filter employs series inductors, parallel capaci-
tors, and in some cases, a clamping device. In-
stalled between a radio transmitter and the
Input Output
utility lines, such a filter can choke off radio-
frequency (RF) current and help keep utility
wiring from acting as an antenna. Installed in the
linear transformer
line filter • linkage

line-of-sight distance The maximum distance
over which an ultra-high-frequency (UHF) or mi-
crowave signal can be directly transmitted along
the surface of the earth. It is slightly more than
the maximum optical line-of-sight distance.
line oscillator See LINE-TYPE OSCILLATOR.
line plug The plug terminating a line cord. Also see
line printer A machine that prints the results of a
computer run, line by line.
line radio See WIRED RADIO.
line regulation Automatic stabilization of power-
line voltage.
line-sequential system The color television sys-
tem in which the image is reproduced by means
of primary color lines (red, green, and blue) se-
quentially beamed across the screen of the pic-
power cords of home entertainment equipment, ture tube. Compare DOT-SEQUENTIAL SYSTEM
such as stereo audio amplifiers, line filters can and FIELD-SEQUENTIAL SYSTEM.
keep RF from entering the apparatus through lines of cleavage See CLEAVAGE.
the power supply. 2. A circuit containing paral- lines oscillator See LINE-TYPE OSCILLATOR.
lel capacitors and/or series inductors, installed line supervision In electronic security systems, a
in a twisted-pair telephone line to reduce or method of monitoring circuit characteristics to
eliminate the effects of EMI and transients in a detect possible tampering.
telephone set. line switch 1. The main power-line switch to a sys-
linefinder A switching device that finds one of a tem. 2. Within a piece of electronic equipment,
group of calling telephone lines and connects it to the switch that opens and closes the circuit to the
a trunk, connector, or selector. incoming power line.
line frequency 1. The frequency of power-line volt- line-type amplifier A radio-frequency amplifier in
age in the United States, 60 Hz. 2. The rate at which the tuned circuits are transmission lines
which the horizontal lines are traced in a video consisting of parallel wires, rods, or tubing, or of
image. Also see HORIZONTAL FREQUENCY. coaxial cable sections.
line group 1. A group of signals sent by wire trans- line-type oscillator A radio-frequency oscillator in
mission. 2. The frequency spectrum occupied by which the tuned circuits are transmission lines
a group of signals sent by wireless transmission. consisting of parallel wires, rods, or tubing, or of
line leakage Resistance between insulators of two coaxial cable sections.
wires in a telephone line loop. line unit In a wire data transmission system, the
line loss The sum of energy losses in a transmis- terminal unit, or device that converts the text sig-
sion line. nals into electrical impulses and vice versa.
lineman A technician who works mainly with tele- line voltage 1. The voltage between the conductors
phone or telegraph lines. in a power line. 2. The voltage between the con-
line matching transformer A device that provides ductors of a transmission line.
an impedance match in an audio circuit, and also line-voltage drop See LINE DROP.
can adapt balanced to unbalanced audio trans- line-voltage monitor See POWER-LINE MONI-
mission lines (or vice versa). TOR.
line noise 1. Electrical noise (as received by a ra- linguistics The study of languages, including
dio) arising from fluctuations of current or voltage structure, symbology, and phonetics.
in a power line. 2. Noise in a data transmission link 1. The small coupling coil used in link cou-
line. pling. 2. A communication path between two ra-
line of flux 1. A line (usually curved) depicting the dio facilities for the purpose of extending the
points of equal-intensity field strength in the range of one, as between a remote pickup point
vicinity of an electric charge or a charged body. and a broadcast transmitter. 3. A data connec-
Also see FLUX. 2. A line depicting the points of tion between two different computers. 4. The act
equal-intensity field strength in the vicinity of a or process of creating a signal path or data con-
magnetic pole or a magnetized body. Also see nection, as defined in 1, 2, or 3. 5. In a digital
FLUX. computer, a branch instruction, or an address in
line-of-sight communication Radio communica- such an instruction, used to leave a subroutine to
tions between points located so that a straight return to some point in the main program.
line between them does not pass through the linkage Coupling between separated conductors or
earth, or through any major obstructions. Also devices through the medium of electric or mag-
see LINE-OF-SIGHT DISTANCE. netic lines of flux.
412 link circuit • liquid-pressure alarm

Back glass
link circuit A closed-loop coupling circuit having
and polarizer
two coils of a few turns of wire; each coil is placed
near one of the circuits to be coupled.
link coupling Low-impedance coupling via a small
(usually one-turn) input or output coil fed by a Sealed-in
twisted pair or a coaxial line. fluid
Front glass
Input C1 L1 L2 C2

link coupling

linked subroutine A subroutine, entered by a
branch instruction from a main routine, that ex-
ecutes a branch instruction returning control to
the main routine. liquid-crystal display
link fuse A fuse consisting of an exposed length of
fuse wire.
link neutralization Neutralization achieved by improved in recent years with the advent of
out-of-phase current fed back via link coupling active-matrix, also known as thin-film-transistor
from the output to the input of an amplifier. Also (TFT), displays.
called INDUCTIVE NEUTRALIZATION. liquid-filled transformer A transformer filled with
lin-log receiver A radar receiver whose amplitude a protective liquid insulator, such as oil.
response is linear for small signals, but logarith- liquid-flow alarm An electronic circuit that actuates
mic for large ones. an alarm when the flow of a liquid through pipes or
lip microphone A small microphone operated other channels changes from a desired rate.
close to or in contact with the lips. liquid-flow control A servo system that automati-
liquid A state of matter characterized by a level of cally maintains or corrects the rate of liquid flow
molecular motion intermediate between that of through pipes or other channels.
gases and solids; liquids have the ability (like liquid-flow gauge See LIQUID-FLOW METER.
gases) to take the shape of a container and are only liquid-flow indicator See LIQUID-FLOW METER.
slightly compressible. Compare GAS, PLASMA, liquid-flow meter An instrument that indicates
and SOLID. Also see STATE OF MATTER. the rate at which a liquid moves through pipes or
liquid absorption For a solid material, such as di- other channels.
electric, the ratio of the weight of liquid absorbed liquid-flow switch In a liquid-cooled system, a
by the material to the weight of the material. switch that actuates an alarm when the liquid
liquid capacitor See WATER CAPACITOR. slows or stops.
liquid cell See ELECTROLYTIC CELL. liquid-jet oscillograph A graphic recorder using
liquid conductor See ELECTROLYTE. an ink-jet galvanometer to trace the pattern on a
liquid cooling Use of circulating water, oil, or paper chart.
other fluid to remove heat from components or liquid laser A laser in which the active material is
equipment, such as microprocessors or power a liquid.
amplifiers. liquid-level alarm An electronic device that actu-
liquid crystal A liquid exhibiting some of the char- ates visual or audio signal devices when the sur-
acteristics of a crystal. Also see NEMATIC CRYS- face of a liquid inside a tank rises or falls to a
TAL and SMECTIC CRYSTAL. predetermined level.
liquid-crystal display Abbreviation, LCD. A flat- liquid-level control A servo system that automati-
panel display noted for its thin profile, light cally maintains the liquid in a tank at a predeter-
weight, and low power consumption. The sim- mined level.
plest devices are used in calculators, meters, liquid-level gauge An electronic system that pro-
wristwatches, and radios. More sophisticated vides direct readings of the level of a liquid in a
displays are used in computers and portable tank.
video units. This type of display can operate at a liquid-level indicator See LIQUID-LEVEL GAUGE.
much lower voltage than a cathode-ray tube liquid-level meter See LIQUID-LEVEL GAUGE.
(CRT). This makes it ideal for portable electronic liquid load See WATER LOAD.
systems in which batteries are used. Older liquid-pressure alarm An electronic circuit that
displays of this type can be difficult to read from actuates an alarm when the pressure of a liquid
certain viewing angles. This situation has changes.
liquid-pressure control • lm-hr

liquid-pressure control A servo system that auto-
matically maintains or corrects liquid pressure in
pipes or other channels. Left- Right-
liquid-pressure gauge See LIQUID-PRESSURE channel channel
METER. speaker speaker
liquid-pressure indicator See LIQUID-PRESSURE
liquid-pressure meter An instrument that pro-
vides direct readings of liquid pressure in a pipe
or other channel.
liquid-pressure switch A switch that actuates an Listening
external circuit or device when the pressure of a angle
liquid changes.
liquid rheostat See WATER RHEOSTAT.
liser An oscillator that produces an extremely pure
microwave carrier signal.
LISP A digital-computer language written in the
form of lists. A program can be directly inter-
preted as data, and vice versa. The entire lan- Listener
guage is derived from a few basic functions.
Programs are easy to debug. It is used in artificial listening angle
intelligence (AI) research. Also see LANGUAGE.
Lissajous figure Any one of several curves result-
ing from the combination of two harmonically re- to supply 1.5 to 3.5 volts, depending on the par-
lated sine waves. These figures are familiar in ticular chemistry used. These cells can last for
electronics; they are obtained when signals are years in very-low-current applications such as
applied simultaneously to both axes of an oscillo- memory backup.
scope. It is also called Lissajous pattern. Litzendraht wire See LITZ WIRE.
list 1. To print serially the records in a file or in Litz wire A woven wire having a number of copper
memory. 2. To print (instruct a computer to dis- strands, each separately enameled to insulate it
play) every item of input data in a program. 3. A from the others. The wire is woven so that inner
one-dimensional array of numbers. strands come to the surface at regular intervals.
listener fatigue Physiological symptoms, such as It is noted for its low losses at radio frequencies.
headaches, caused by prolonged listening to cer- live 1. Electrically activated (i.e., sustaining volt-
tain sounds (e.g., a pure sine wave or poorly re- age or current). 2. Being broadcast as it occurs.
produced music). 3. Acoustically reflective, as in a LIVE ROOM
listening angle In stereo sound reproduction, the (contrasted with one that is acoustically ab-
angle between the speakers, with respect to the sorbent).
listener. This angle can vary from zero to 180 de- live end 1. In a recording or broadcasting studio,
grees. Larger angles result in increased apparent the part of the room in which the acoustic con-
channel separation. centration is greatest. 2. In a utility circuit, the
listening test The subjective evaluation of audio wire or terminal that carries 117 volts alternating
equipment by listeners. current (the ungrounded end).
liter Abbreviation, l. A metric unit of volume equal live end/dead end Pertaining to a room that is
to 1.0567 U.S. liquid quarts or 0.908 U.S. dry acoustically reflective (live) at one end, and
quart. A liter is the volume of 1 kilogram of water acoustically absorbent (dead) at the other end.
at 4¯C and under a pressure of 1 pascal. live room A room with little or no acoustically ab-
literal operands It is usually applicable to source sorbent material in its ceiling, walls, and floor,
language instructions, operands that specify the with the result that echoes and reverberation are
value of a constant, rather than an address of a pronounced. Compare DEAD ROOM.
location in which the constant is stored. lix Abbreviation of LIQUID CRYSTAL.
lithium Symbol, Li. An element of the alkali-metal LK band A section of the L BAND that extends from
group, and the lightest elemental metal. Atomic 1.150 to 1.350 GHz.
number, 3. Atomic weight, 6.941. LL band A section of the L BAND that extends from
lithium battery See LITHIUM CELL. 510 to 725 MHz.
lithium cell A type of electrochemical cell with ex- LLL Abbreviation of LOW-LEVEL LOGIC.
ceptional energy-to-mass ratio and long shelf life. lm Preferred abbreviation of LUMEN.
lm/ft2 Abbreviation of lumens per square foot. Also
There are several variations in the chemical
makeup; they all contain lithium, a light, highly see LUMEN.
reactive metal. These units can be manufactured lm-hr Abbreviation of LUMEN-HOUR.
414 lm/m2 • loading disk

lm/m2 Abbreviation of lumens per square meter.
Also see LUMEN and LUX.
lm/W Abbreviation of lumens per watt, a unit of lu-
Shortened radiator
minosity. Also see LUMEN.
ln Representation of the natural (base-e) logarithm
function (see NAPIERIAN LOGARITHM). Also
written loge.
L network An impedance-matching circuit, filter,
or attenuator whose schematic representation re- Loading coil
sembles an inverted letter L.
LO Abbreviation of LOCAL OSCILLATOR.
lo Abbreviation of low, usually as a prefix or sub-
script. Also abbreviated L.
load 1. Also called electrical load. A device or circuit
that is operated by the electrical power output of
another device or circuit. Examples: speaker, light
bulb, power amplifier, antenna system. 2. Also
called mechanical load. The mechanical power feed
output demanded of a machine”especially a mo- line
tor. 3. To fill an internal computer storage with in-
formation from an external storage [e.g., from a
magnetic disk to a computer™s random access
memory (RAM)]. 4. To add inductors and/or ca-
pacitors to an antenna system to alter the charac-
teristics of the system”especially the resonant Radial
frequency. 5. To adjust the output circuit of a
radio-frequency power amplifier for optimum
energy transfer to the antenna system.
load-and-go Automatic coding in which a user™s
(source) program is translated automatically into
loaded antenna
machine language and stored.
load capacitance 1. The capacitance present in an
load/haul/dump Abbreviation, LHD. A remote-
electrical load (see LOAD, 1). 2. A capacitance
controlled or computer-controlled robot used in
used as an electrical load.
mining and construction work. Under the direc-
load capacity 1. In pulse-code modulation, the
tion of a human operator or a computer, it loads,
level at which a sine-wave signal has peaks coin-
hauls, and dumps materials (hence its name). It
ciding with the plus/minus virtual decision val-
can use various navigation methods, including
ues of the encoder. 2. The maximum number of
beacons, computer maps, position sensors, and
signals that a medium or line can carry without
vision systems.
serious degradation of reception.
load impedance Symbol, Z L. The impedance pre-
load circuit 1. The circuit that forms the load, or
sented by a load connected to a generator or other
power-consuming portion, of a system. 2. A cir-
cuit that facilitates transfer of power to a load.
loading 1. The matching of source impedance to
load coil See WORK COIL.
load impedance, usually by means of the intro-
load current The current flowing in a load. See
duction of an inductance or capacitance into the
load itself. 2. Any form of impedance matching.
load division A method of connecting two or more
3. The addition of inductance and/or capacitance
power sources to a single load, for optimum
to an antenna system to alter the characteristics
power transfer.
of the system”especially the resonant frequency.
loaded antenna An antenna incorporating a
4. The modification of the acoustic impedance of
a loudspeaker.
crease its electrical (effective) length. See LOAD-
loading coil An inductor inserted in a circuit to in-
crease its total inductance or to provide some
loaded line A transmission line in which inductors
special effect, such as canceling capacitive reac-
or capacitors are inserted at appropriate points to
alter the characteristics of the line.
loading disk Also called capacitance hat. A metal
load end The end of a transmission line to which a
disk mounted atop a vertical antenna to increase
radiator or receiver is connected.
its effective length and thereby lower its resonant
load flicker Fluctuations in the brightness of
frequency. It also increases the bandwidth of the
lamps, caused by intermittent loading of the
power line by other devices.
loading factor • local side

loading factor The ratio of source impedance to lobing 1. In a transmitting or receiving antenna,
load impedance before the introduction of loading the effect of ground reflection, resulting in phase
circuits. reinforcement (lobes) at some elevation angles
loading inductance 1. The inductance present in and phase opposition (nulls) at other angles.
a load. 2. An inductance used as a load. 2. The pattern of secondary maxima in the
loading routine Also called loading program. A radiation response of a directional antenna.
routine permanently in memory; it allows a pro- local action Electrolysis between separate areas of
gram to be loaded into memory from an external a single electrode immersed in an electrolyte. The
storage medium. action is caused by impurities at different spots
load life The longevity of a device in terms of the in the electrode metal, causing one spot to act as
number of hours it can withstand its full power an anode and the other as a cathode, thereby cre-
rating. ating a small battery cell.
load line In a group of voltage-current (EI) curves, local alarm In security applications, a visible
a line connecting points of equal resistance (E/I) and/or audible alarm that can be seen and/or
that are equal to a particular value of load resis- heard easily throughout the protected zone.
tance (impedance). local area network Abbreviation, LAN. A group of
load power The power dissipated in a load. computers and/or terminals that are linked to-
load regulation Automatic stabilization of load re- gether within a relatively small geographic area,
sistance (impedance) at a constant value. such as a college campus. Interconnections are
load resistance 1. The resistance present in a usually made via cable. There are several differ-
load. 2. A resistance used as load. ent configurations, called topologies.
load stabilizer A device for holding load current or local battery In wire telephony, a battery installed
load voltage to a constant value. on the subscriber™s premises.
loadstone Alternate spelling of LODESTONE. local broadcast station A standard broadcast sta-
load termination The load connected to the out- tion licensed in the local service. See LOCAL
put of a circuit or device as the terminal element CHANNEL and LOCAL STATION.
in a circuit or system. local channel A channel in the standard ampli-
load voltage The voltage developed across a load. tude-modulation (AM) broadcast band, intended
load-voltage stabilization Automatic regulation of to serve only the area near the station. Transmit-
load voltage. ter power and operating time are restricted to
load wattage See LOAD POWER. prevent long-distance propagation.
lobe In the directivity pattern of a transducer, a fig- local control The control of a radio transmitter
ure, such as a circle or ellipse enclosing an area from the site (in contrast to remote control).
of intensified response. Applicable especially to local feature focus In robotic systems, the use of
antennas. only a small portion of the available image data to
perform a function. The robot computer recog-
nizes and acts on the data it needs, disregarding
the rest.
80 90 80 70 local feedback Feedback within a circuit stage.
70 60 localizer A radionavigation transmitter whose sig-
50 nal guides aircraft to the centerline of a runway.
40 local oscillator Abbreviation, LO. In a wireless
transmitter, one of the oscillators that contributes
30 to the signal that is ultimately modulated and
20 transmitted. The LO output is mixed with the out-
20 9° put of a variable-frequency oscillator (VFO). The
5 LO frequency can be switchable at increments of
several hundred kilohertz (500 kHz and 1000 kHz
30° are typical), facilitating band changes when mixed
5 with the VFO output. In some transmitters, the
LO can operate at a single, fixed frequency if the
VFO tunes over an exceptionally wide range.
15 local program A program that originates at the
40 same single broadcast station from which it is
40 transmitted.
50 local reception The reception of signals from local
70 80 90 80 70 stations. Compare LONG-DISTANCE COMMUNI-
local side The group of circuits and components
associated with a communications terminal at a
lobe (pattern of
given location.
horizontal half-wave antenna)
416 local station • logarithmic voltmeter

local station A station situated within the same transcendental number e, approximately equal
general area as the receiver, as opposed to a dis- to 2.71828. See COMMON LOGARITHM and
local system library A computer program library logarithmic amplifier An amplifier whose output-
containing standard software associated with a signal amplitude is proportional to the logarithm
specific system. of the input-signal amplitude.
local transmission The sending of signals to re- logarithmic curve A graphical representation of a
ceivers in the same general locality as the trans- logarithmic function, having the form y = k logax,
mitter, as opposed to long-distance transmission. where k is a nonzero real-number constant, and
local trunk In a telephone system, the intercon- a is a positive real number (the logarithmic base).
necting line between local and long-distance logarithmic decrement See DECREMENT.
lines. logarithmic graph Also called log-log graph. A
location In digital computer operation, a memory graph in which the x and y axes are both in-
position (often a register) specified by an address cremented logarithmically. Compare SEMILOG-
and usually described in terms of the basic stor- ARITHMIC GRAPH.
age unit a particular system uses (e.g., a charac- logarithmic horn A horn whose diameter varies
ter is a location in a character-oriented machine). directly, according to the logarithm of the dis-
location counter A register in the control section placement along the axis. See HORN.

of a computer containing the address of the in- logarithmic mean See GEOMETRIC MEAN.
struction being executed. logarithmic meter A current meter or voltmeter

locked groove A continuous blank groove around whose deflection is proportional to the logarithm
the inside of a phonograph record. When the disc of the quantity under measurement. The incre-
is done playing, this groove keeps the stylus from ments on the scale of such an instrument are
running into the label or sliding across the disc. closer together in the upper portion.
locked oscillator 1. A fixed-frequency oscillator, logarithmic rate of decay See EXPONENTIAL DE-
such as a crystal-controlled oscillator. 2. See CREASE.
BRADLEY DETECTOR. logarithmic rate of growth See EXPONENTIAL
lock-in A state of synchronism, as when a self- INCREASE.
excited oscillator is synchronized (locked-in) with logarithmic response 1. Response in which the

a standard-frequency generator. value of a dependent variable is at every point
lock-in amplifier A detector that makes use of a proportional to the logarithm of the independent
balanced amplifier. The output is the difference variable. 2. A type of response in which a quan-
between the collector or drain currents of the two tity (such as current) varies directly with the log-
devices. arithm of another quantity (such as voltage).
locking circuit See HOLDING CIRCUIT. logarithmic scale A graduated scale in which the
locking relay See LATCHING RELAY. coordinates are positioned, according to the loga-
lock-in relay See LATCHING RELAY. rithm of the actual distance from the origin.
lock-out 1. To prevent a hardware unit or routine logarithmic voltmeter See LOGARITHMIC
from being activated (e.g., when there would be a METER.
conflict between operations using the same areas
of memory). 2. A safeguard against an attempt to
Linear Logarithmic
refer to a routine in use.
lock-up relay An electromagnetic relay that can be 1
locked in the actuated state nonmechanically
(i.e., by means of an electromagnet or permanent
locus The set of all points located by stated condi- 4
tions (e.g., the locus of secondary points that are
all equidistant from a primary point is a sphere).
lodestone A natural magnet; a form of the mineral
magnetite. Also spelled loadstone. 10
log 1. Abbreviation of LOGARITHM. 2. A continu-
ous record of communications kept by a station,
or a record of the operation of an equipment.
log10 Abbreviation of common logarithm (base-10
logarithm). Also called Briggsian logarithm.
logarithm Abbreviation, log. The power y to which
a fixed number a, called the base, must be raised
to equal a given number x. Suppose x = ay, where 100
a, x, and y are real numbers. Then, logax = y. The
most common logarithmic bases are 10 and the logarithmic scale

loge • logic probe

loge Abbreviation of logarithm to the base e (the logic comparison An operation in which two op-
NAPIERIAN LOGARITHM). Also written ln. erands are compared for equal value.
logic 1. In digital circuits, the mathematics dealing logic connectives Words connecting operands in a
with the truth or falsity of statements (repre- logic statement; the truth or falsity of the state-
sented by variables) and their combinations. Also ments can be determined from their content and
see SYMBOLIC LOGIC. Generally, “truth” is rep- the connectives™ meanings.
resented by the binary digit 1, and “falsity” is rep- logic diagram 1. A graphic representation of a
resented by the binary digit 0. 2. Collectively, the logic function (e.g., AND, NAND, NOR, OR, and
switching circuits and associated hardware for XOR). 2. The design of a device or system repre-
implementing digital functions (see 1), such as sented by graphic symbols for logic elements and
AND, NAND, NOR, OR, etc. their relationships.
logical decision During a computer program run,
a choice between alternatives based on specified
conditions. For example, one alternative path in a AND
routine might be selected because an intermedi-
ate result was negative.
logical diagram A schematic diagram showing the
interconnection between gates of a logic circuit.
logical equivalence The condition in which two
logical statements have identical truth value for
all possible combinations of truth value of their
constituents. ’
AB + C
logical file A data set composing one or several
logical records. 0 0 0 1
logical implication For logical statements x and y, 0 0 1 0
the condition that y is true whenever x is true: If
0 1 0 1
x, then y.
logical operation 1. An operation using logical op- 0 1 1 0
erators: AND, NOR, OR, and NAND. 2. A process- 1 0 0 1
ing operation in which arithmetic is not involved
1 0 1 0
(e.g., a shift).
logical operator A word or symbol representing a 1 1 0 1
logic function operating on one or more operands. 1 1 1 1
Examples: NOT, OR, AND, NOR, and NAND.
logical shift A shift operation in which digits in a logic diagram and truth table
word are moved to the left or right in circular fash-
ion; digits displaced at one end of the word are re-
turned at the other. Also called CYCLIC SHIFT. logic diode See COMPUTER DIODE.
logic array In logic circuits, a redundant arrange- logic flowchart The logical steps in a program or
ment of identical components in a single package. subroutine represented by a set of symbols.
logic circuit In digital systems, a gating or switch- logic function An expression for an operation in-
ing circuit that performs such logical operations volving one or a combination of logic operators.
as AND, NAND, NOR, OR, and XOR. It can use logic gate See LOGIC CIRCUIT.
diodes, transistors, charge-coupled devices, tun- logic input current In an integrated circuit, the
nel diodes, thyristors, ferroelectric elements, mag- input current to the logic gate at a certain voltage
netic-core elements, or a combination of these. It value.
usually consists of diodes and transistors fabri- logic input levels The range of voltages over which
cated onto an integrated-circuit (IC) chip. the logic trip level occurs, from low to high or high
to low. It is usually expressed in volts for the low
state and the high state; for example, low is “1 to
+2 volts, high is +4 to +6 volts.
logic instruction A command to execute a logical
AND NOT OR function.
logic level 1. One of the two logic states 0 or 1 (on
or off, high or low). 2. Of the two logic states, that
which represents the “true” condition. 3. The volt-
age amplitude of digital signals in a logic system.
logic probe A test probe with a built-in amplifier
and (usually) indicating LEDs; its tip is touched
to various test nodes in a digital logic circuit to
logic circuits
(or gates) trace logic levels and pulses.
418 logic relay • long-term input offset voltage stability

logic relay See BISTABLE RELAY. longitudinal parity Parity associated with bits
logic swing In a logic circuit, the difference be- recorded on one track of a magnetic storage
tween the voltage corresponding to the high state medium to indicate whether the number of bits is
and the voltage corresponding to the low state. even or odd.
logic symbol 1. A symbol used to represent a logic longitudinal redundancy A computer condition,
element in a circuit diagram. 2. A symbol used to generally affecting magnetic tape records, in
represent a logic connective. which the bits in each track of a record do not
log-log graph See LOGARITHMIC GRAPH. meet the required parity, as determined by a
LOGO A high-level computer programming lan- LONGITUDINAL REDUNDANCY CHECK.
guage used for robot control and as an education longitudinal redundancy check A parity check
aid. It is especially useful for teaching children performed on a block of characters or bits (for ex-
how to operate computers and computerized ample, on a track of a magnetic disk). A parity
robots. Statements are simple enough so that character is generated and transmitted as the
elementary-school children can learn to write last character of the block; thus, each longitudi-
short programs. nal block has either even or odd parity.
log-periodic antenna Also called log-periodic dipole longitudinal wave A wave in which the movement
array (LPDA). A broad-spectrum, multiband direc- of particles in a medium is parallel with the di-
tional antenna in which the lengths and spacing of rection of propagation.
the radiator and elements increase logarithmically
from one end of the antenna to the other.
Max Max Max Max
log polar navigation A computerized navigation
system in which polar-coordinate data is con-
verted into rectangular-coordinate data. In the
transformation process, the logarithm of the ra-
dius (range) is taken. This results in improved
image resolution at close range, although it sacri-


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