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external armature In a dynamo-type machine, an
armature that rotates around the outside of the
field magnets, as opposed to the usual (inside) ar-
Sensitivity rangement.
external capacitor A high-value capacitor con-
nected externally to an oscillator or sweep gener-
ator to lower its frequency.
external circuit A circuit or subcircuit connected
and external to a main equipment.
external controls 1. Control devices that are con-
nected to, but operated away from, a main cir-
cuit. 2. Manual or screwdriver-adjusted controls
that are mounted on the panel of an equipment,
as opposed to those mounted in the case or be-
Photovoltaic Meter
hind the panel.
cell
external critical damping resistance The value of
exposure meter external resistance that must be connected to a
galvanometer or other meter to produce critical
damping.
external damping device A resistor or short-
expression control A volume control in an elec-
circuiting bar connected temporarily between the
tronic organ.
terminals of a meter to keep its movement immo-
extended double Zepp antenna See DOUBLE-
bile during transportation.
EXTENDED ZEPP ANTENNA.
272 external feedback • extreme


external feedback Negative or positive feedback Extra-class license An amateur-radio license that
through a separate path outside of and around conveys all available amateur operating privileges
the main circuit. Example: negative feedback in the United States. The highest class of ama-
through a resistance-capacitance (RC) path be- teur license.
tween the output terminals and the input termi- extract 1. To remove a signal or quantity from
nals of an amplifier. some product containing it, or from its source.
Examples: extracting a fifth harmonic from a
complex signal, extracting the direct-current (dc)
component from a signal containing both alter-
nating current (ac) and dc. 2. To derive a factor
(e.g., to extract a root). 3. To separate certain
classes of information from an aggregate of infor-
mation.
extract instruction In computer operations, the
instruction to generate a new word by the serial
arrangement of designated segments of specified
words.
extractor 1. A circuit or device for removing a sig-
nal (or a signal component) from another circuit
External or device. A demodulator probe, for example, ex-
feedback tracts the modulation from a modulated signal.
2. A device for removing used active devices from
a circuit board. Such extractors can also employ
heat to desolder, as well as remove the devices.
external feedback
extraneous component A usually undesired in-
herent effect that results from the physical
external impedance Load impedance (i.e., an nature of a component or device. Examples:
impedance connected to the output terminals of a distributed capacitance of a coil, internal induc-
generator or amplifier). tance of a capacitor.
external load See EXTERNAL IMPEDANCE. extraneous emission Undesired emission from a
external loudspeaker See EXTERNAL SPEAKER. transmitter (e.g., excessive harmonics).
externally caused chatter In a relay, contact extraneous response The unintended response of
chatter caused by mechanical vibration outside a circuit or device (e.g., image response in a su-
of the relay. perheterodyne communications receiver).
externally caused failure Failure of a circuit or extraneous root In the solution of an equation de-
component resulting from unfavorable environ- rived from another equation, one or more roots
mental factors. that satisfy the derived equation but not the orig-
external memory In computer operations, a mem- inal one.
ory unit outside of the computer mainframe. extraneous signal A superfluous and potentially
external power supply A power supply unit situ- interference-causing signal.
ated apart from the powered equipment. Such extranuclear Outside the nucleus of an atom.
separation is helpful in eliminating the disturbing extraordinary ray Of the two rays resulting from
effects of heat, hum, and vibration associated the double refraction of electromagnetic waves,
with internal power units. the one that does not follow the usual laws of re-
external Q For a microwave tube, the quantity fraction. Also see X WAVE.
1/(1/Q1 + 1/Q2), where Q1 is the loaded Q and Q2 extraordinary wave See X WAVE.
is the unloaded Q. extrapolar 1. Outside of electrical or magnetic
external S-meter A signal-strength meter con- poles. 2. Not between electrical or magnetic poles.
nected to a receiver, but not installed in its panel. extrapolation Estimation of values beyond the
external speaker A loudspeaker that doesn™t share range of available data. An example is the exten-
an enclosure with an amplifier, receiver, or other sion of a curve beyond its final plotted point to de-
device that drives it. Such isolation is helpful in termine a value for a variable. There is always
eliminating the undesirable effects of vibration some margin for error, which increases as the
and acoustic feedback. process is extended further and further beyond
external storage In computer operations, storage the range of actual data values. Commonly done
media (such as magnetic diskettes or tapes) that by computers (e.g., prediction of the probable
are outside of the computer. path of a hurricane 12, 24, 36, and 48 hours in
extinction potential See DEIONIZATION POTEN- advance).
TIAL. extrared See INFRARED.
extinction voltage See DEIONIZATION POTEN- extraviolet See ULTRAVIOLET.
TIAL. extreme 1. The lowest or highest value of a
273
extreme • E zone


quantity. 2. The lowest or highest point of the de- extrusion The process of forming a material such
pendent variable in the range of a function. 3. An as metal or plastic, by forcing it through dies.
unusual value for a parameter (e.g., temperature Many pieces of electronic hardware are mass pro-
extreme and pressure extreme). duced in this manner. Examples are insulating
extremely high frequency Abbreviation, EHF. A rods and tubes, metal cans, and metal tubing.
frequency near the upper limit of the radio-fre- eye-in-hand system In robotics, a scheme that
quency spectrum”especially one in the 30- to uses a vision system, servo, and microprocessor
300-GHz band. to precisely manipulate an END EFFECTOR, such
extremely low frequency 1. Abbreviation, ELF. as a robot gripper (“hand”). A camera (the “eye”) is
Pertaining to a signal or current within the audio- contained in the end effector itself, and is de-
frequency (AF) range, but not used for audio ap- signed to work at close range (i.e., approximately
plications. 2. Electromagnetic emissions from a one meter down to a fraction of a millimeter).
cathode-ray tube (CRT), resulting from the cur-
rents in the deflecting coils and/or electron
beam. 3. The 60-Hz electromagnetic field gener-
ated by utility power lines and wiring.
extrinsic base-resistance/collector-capacitance
product Units: seconds, milliseconds, and mi-
croseconds. For a bipolar transistor, the product
RBCC, where RB is the base resistance and CC is
the collector capacitance. This product is a time
constant that determines the high-frequency op-
erating limit of the transistor.
extrinsic conductance For a material, the con-
ductance resulting from impurities or such exter-
nal factors as environmental conditions.
extrinsic properties For a semiconductor mate-
rial, properties resulting from doping (e.g., altered
resistivity or majority/minority carrier differenti-
ation). Also see EXTRINSIC SEMICONDUCTOR.
extrinsic semiconductor A semiconductor mate-
rial, such as germanium or silicon, to which a
controlled amount of a suitable impurity material
has been added to give the semiconductor a de- eyelet connection A connection made by fasten-
sired resistivity and polarity. Compare INTRINSIC ing conductors together with an eyelet or by sol-
SEMICONDUCTOR. dering leads or pigtails to an eyelet.
extrinsic transconductance Symbol, gm. For a eyepiece A small lens system for viewing an oscil-
bipolar transistor, the first derivative of collector loscope screen through a camera setup.
current, with respect to base-emitter voltage. It is EZ Symbol for voltage drop across an impedance.
the ratio of a small change in collector current E zone A portion of the earth including most of the
(dIC) to the small change in base-emitter voltage eastern hemisphere. When propagation forecasts
(dVBE) that produced it, collector voltage being are made, this region is one of three longitude
constant; gm = dIC/dVBE. zones specifie
F 1. Symbol for FORCE. 2. Symbol for FLUORINE. of permanent pictures, writing, and other graphic
3. Abbreviation of FAHRENHEIT. 4. Abbrevia- material.
tion of FARAD. 5. Abbreviation of FERMI. 6. Sym- facsimile receiver The complete device or system
bol for FOCAL LENGTH. 7. Symbol for FUSE. that selects, amplifies, and demodulates a picture
8. Symbol for FARADAY CONSTANT. signal received up from the air, wires, or cable,
f 1. Abbreviation of FEMTO. 2. Symbol for FRE- and uses the elements of this signal to reproduce
QUENCY. 3. Symbol for FUNCTION. the picture. Also see FACSIMILE.
F0 Symbol for DAMPING FACTOR. facsimile recorder The machine that puts a trans-
F1 layer The lower part of the ionosphere™s F RE- mitted facsimile image on paper.
GION. Also called F1 region. facsimile transmitter The complete device or sys-
F2 layer The upper part of the ionosphere™s F RE- tem that generates signals depicting graphic ma-
GION. Also called F2 region. terial (pictures, writing, printing, etc.) and sends
fA Abbreviation of FEMTOAMPERE. them to a distant point via cable, wire lines, or ra-
fabrication tolerance The amount of variation dio for subsequent reproduction. Also see FAC-
that can be tolerated in the manufacture of com- SIMILE.
ponents. factor 1. A data element that is an operand in an
Fabry-Perot interferometer A resonant cavity, of- arithmetic operation. 2. To find the two or more
ten used with lasers, that has mirrors at each numbers whose product is the number being fac-
end; the interferometer produces the optical tored. 3. One of two or more numbers whose
equivalent of standing waves. product is the number being factored.
face 1. A flat crystal surface whose orientation can factorial Symbol, !. For an integer n, the product of
be expressed as its position relative to other all positive integers up to and including n. Thus,
5! = 1 — 2 — 3 — 4 — 5 = 120. The term n! is read “n
faces. 2. The viewer™s side of a screen. 3. The
scale part of a meter. factorial.”
face material In a tape recorder, the plastic used factor of merit See FIGURE OF MERIT.
to coat the face of a head. factor of safety See SAFETY FACTOR.
face-parallel cut See Y-CUT CRYSTAL. fade in To gradually increase an audio or video sig-
face-perpendicular cut See X-CUT CRYSTAL. nal”especially for recording.
face side The side of pressure-sensitive insulating fade out 1. To gradually decrease an audio or video
tape that is coated with adhesive. signal”especially for recording. 2. The complete
facom A radionavigation system that operates by disappearance of a radio communications signal.
means of phase comparison at low frequencies. See FADING.
Effective over long distances and under poor con- fader 1. In sound amplification systems, an atten-
ditions. uator circuit that enables the operator to fade out
facsimile Also called fax. The transmission and re- one signal and fade in another. Ordinarily, a
ception, through the medium of radio or by wire, fader does not provide mixing action. 2. In an au-


Copyright © 2001 by The McGraw-Hill Companies, Inc.
Click here for Terms of Use.
275
fader • fan-out


tomotive high-fidelity sound system, a control cent to 10 percent of its peak amplitude. Com-
that adjusts the volume of the front speaker set pare RISE TIME.
and rear speaker set. Usually, this is a single false add A logic add (i.e., addition without car-
knob; increasing the front volume decreases the ries).
rear volume, and vice-versa. false alarm 1. Improper operation of an electronic
fading 1. Repeated increases and decreases of ra- security system, resulting in actuation of the
dio communications signal amplitude at the re- device when no breach of security has occurred.
ception point. Fading of a radio wave results from 2. In radar, the presence of a false echo that
multiple propagation paths from transmitter to causes the attendant circuits or personnel to act
receiver, causing the received waves to arrive in as though an enemy target is present.
constantly varying phase relationships. 2. In a false error A condition in which a computer sys-
cell or battery power supply, a gradual loss of tem erroneously signals the existence of an error.
power-delivering capability that occurs during false precision See MISLEADING PRECISION.
the discharge cycle. false retrieval The incorrect specification of crite-
ria for information to be selected for retrieval so
that an unwanted item of data is selected. Also
Ionized
called false drop.
layer
family Any group of components, circuits, ratings,
or characteristics, classed together because of
some common or analogous feature or applica-
tion. Examples: IC family, family of curves, and
family of equations.
family of curves A group of curves plotted on the
TX RX
same axes, that depict the performance of a circuit
Earth
or device at several levels of a third parameter (e.g.,
curves showing transistor collector current vs. col-
lector voltage for several levels of base current).
fading

Collector
factory automation The use of robotic devices, to current,
the greatest extent possible, as laborers in manu- Base
milliamps
facturing plants. current,
8_
microamps
Fahnestock clip A flat, sheet-metal spring clip for
holding a wire (usually in a temporary bread-
150
board setup).
6_
Fahrenheit scale A temperature scale on which 100
the freezing point of water is 32 degrees, and the
boiling point of water is 212 degrees. Compare 50
4_
ABSOLUTE SCALE and CELSIUS SCALE.
failsafe Pertaining to devices or circuits that, upon
25
failure, cause no damage or serious malfunction.
2_
failsoft In a computer, a system in which operation
is maintained”even in the event of partial fail- 0
ure. Efficiency is reduced but the computer does
0_
not completely shut down.
_
_




_




_




failure The condition wherein a circuit, system, or 5 10 15
0
device is not operating correctly.
Collector voltage, volts
failure analysis 1. The process of determining the
failure rate for a component, system, or device.
family of curves
2. The process of determining the cause of a
failure.
fan antenna See DOUBLE-V ANTENNA.
failure mode The particular way in which a failure
fan-in 1. A number of inputs entering a common
of equipment or a method occurs.
input terminal. 2. In digital computer operations,
failure unit A unit of machine or device failure:
one failure per billion (109) hours of operation. the number of inputs that can be accommodated
by a logic circuit. Compare FAN-OUT.
fall-in The time when synchronous speed is at-
fan-in circuit A circuit having a number of input
tained in a synchronous motor.
lines entering a common input point. Also see
falling characteristic A NEGATIVE RESISTANCE
FAN-IN, 1.
characteristic.
fan-out 1. One common output terminal feeding a
fall time 1. Decay time. 2. The time required for
number of output lines. 2. In digital computer
the amplitude of a pulse to decrease from 90 per-
276 fan-out • fatigue


operations, the number of outputs that can be fed yond the near field of a loudspeaker (see NEAR
by a logic circuit. Compare FAN-IN. FIELD, 2).
fan-out circuit A circuit in which a number of out- far infrared Also called far IR. The lower-frequency
put lines leave a common output terminal. Also portion of the infrared (IR) spectrum.
see FANOUT, 1. farming robot A robot that performs labor in an
fantasy robot A robot as portrayed in science fic- agricultural setting. Examples: fruit-picking
tion or fantasy. Such robots are usually, but not robot, field-watering robot, cow-milking robot.
always, androids (that is, they have humanoid Such machines are usually overseen by a central
form). Some fictional robot characteristics are computer, via which the farmer can monitor and
later realized. Science fiction can even give roboti- control the robots™ actions.
cists ideas for future designs. far zone See FAR FIELD, 1, 2.
farad (Michael Faraday, 1791“1867) Abbreviation, fast access storage In a computer memory, the
F. The basic unit of capacitance. A capacitor has section from which information can be most
a capacitance of 1 F when a charge of 1 volt per quickly accessed, depending on the relative speed
second across the capacitor produces a current of of other system devices.
1 ampere through it. fast-break, fast-make relay A relay that opens
faraday An electrical quantity approximately equal and closes rapidly.
to 9.65 — 104 coulombs; it is the quantity of elec- fast-break, slow-make relay A relay that opens




Y
tricity required in electrolysis to free 1 gram rapidly and closes slowly.
atomic weight of a univalent element. The equiv- fast charge The rapid charging of a rechargeable




FL
alent, and preferred, unit is the COULOMB. Also cell or battery, particularly of a nickel-cadmium
called Faraday constant. (NICAD) or nickel-metal-hydride (NiMH) device.
Faraday cage See ELECTROSTATIC SCREEN. fast diode See COMPUTER DIODE.
Faraday constant See FARADAY. fast drift The rapid change of a quantity or setting,
AM
Faraday cylinder A cylindrical metal shield placed usually in one direction. Compare SLOW DRIFT.
around electrical equipment or circuits to prevent fast-food robot A robot that prepares and/or
electromagnetic fields from affecting the equip- serves items in a fast-food establishment.
ment or circuits. Robots have not yet gained wide acceptance in
Faraday rotation 1. A change in the polarization of this setting, mainly because of technical difficul-
TE

an electromagnetic wave as it passes through a ties and prohibitive cost. Another problem is
medium. 2. Constant and random fluctuations in that some customers are put off or intimidated
the polarization of radio signals as they pass by robots.
through the earth™s ionosphere. This phenomenon fast-forward Abbreviation, FF or FFWD. In a tape
affects signals having linear polarization at fre- recorder, a mechanism for running the tape
quencies well below 10 GHz. It has little or no ef- through the machine rapidly.
fect on circularly polarized signals, or on signals at fast groove The informationless groove between
frequencies above 10 GHz. It can be a problem tracks on a disk recording.
with some satellite communications links. fast-make/fast-break relay A relay that closes
Faraday effect See MAGNETO-OPTICAL ROTA- and opens rapidly.
TION. fast-make, slow-break relay A relay that closes
Faraday™s disk dynamo See DISK DYNAMO. rapidly and opens slowly.
Faraday shield See ELECTROSTATIC SCREEN. fast-forward playback In a videotape recorder, the
Faraday™s law The voltage induced in a conductor playing back of the tape at faster than real-life
moving in a magnetic field is proportional to the speed. It allows the viewer to move quickly ahead
rate at which the conductor cuts the magnetic in a program, and also to watch the images so as
lines of flux. to know when to resume normal replay.
Faraday™s laws of electrolysis 1. In electrolysis, fast-reverse playback In a videotape recorder, the
the mass of a substance liberated from solution is playing back of the tape rapidly backwards. It al-
proportional to the strength and duration of the lows the viewer to move quickly back in a pro-
current. 2. For different substances liberated by gram, and also to watch the images so as to know
the same current in a certain time, the masses when to resume normal replay.
are proportional to the electrochemical equiva- fast time constant 1. The property of responding
lents of the substances. Also see ELECTRO- quickly to changes in input parameters. 2. In
CHEMICAL EQUIVALENT; ELECTROLYSIS, 1; radar, a method of defeating attempts at jamming
and ELECTROLYTE. by modification of the receiving circuitry.
faradic current The lopsided alternating current fathometer See ACOUSTIC DEPTH FINDER.
produced by an induction coil. fathom 1. To measure the depth of a body of water,
faradmeter An alternate term for MICROFARAD as in the use of sonar for this purpose. 2. A unit
METER. of length (distance) equal to six feet.
far field 1. The region beyond the near field of an fatigue 1. The degradation of the performance of
antenna (see NEAR FIELD, 1). 2. The region be- circuits or materials with time. 2. The tendency of




Team-Fly®
277
fatigue • feedback factor


bodies and materials to weaken, deform, or frac- feedback 1. The transmission of current or voltage
ture under repeated strain. from the output of a circuit or device back to the
fault 1. A defective point or region in a circuit or input, where it interacts with the input signal to
device. 2. A failure in a circuit or device. modify operation of the device. Feedback is posi-
fault current 1. A momentary current surge. 2. A tive when it is in phase with the input, and is neg-
leakage current. ative when it is out of phase. 2. To input the
fault finder A troubleshooting instrument or de- result at one point in a series of operations to an-
vice (e.g., a multimeter). other point; the method allows a system to moni-
fault resilience 1. A design scheme for an elec- tor its actions and make necessary corrections.
tronic or computer device or system so that if a
component or circuit fails, the system will con-
+12 V
tinue to operate, although perhaps at reduced ef-
Feedback
ficiency. The operator is notified of the problem so (negative)
that it can be repaired with minimal downtime. 2.
In a computer system, the property of being as
nearly sabotage-proof as possible.
fault tolerance Total redundancy in an electronic
or computer system so that if a component or cir-
cuit fails, the system will continue to function at Output
full efficiency. Every component has a backup
that automatically takes over in case of failure.
The operator is notified of the problem, so the de- Input
fective part or circuit can be replaced while its
backup keeps the circuit working continuously at
100-percent capacity.
Faure plate A storage battery plate consisting of a
lead grid containing a chemical electrolytic paste.
fax Abbreviation of FACSIMILE.
fc Abbreviation of FOOT-CANDLE.
fc Abbreviation of CARRIER FREQUENCY.
FCC See FEDERAL COMMUNICATIONS COMMIS- feedback, 1.
SION.
fco Abbreviation of CUTOFF FREQUENCY.
feedback amplifier 1. An amplifier whose perfor-
F connector A type of antenna feedline connection
mance (especially frequency response) is modi-
especially common on television receivers and
fied by means of positive, negative or both
videocassette recorders.
positive and negative feedback. 2. An amplifier
F display See F SCAN.
placed in the feedback path of another circuit to
FDM Abbreviation of frequency-division multiplex.
increase the amplitude of feedback.
FE Abbreviation of FERROELECTRIC. See FERRO-
feedback attenuation 1. In an operational-
ELECTRICITY.
amplifier circuit, the attenuation in the voltage
Fe Symbol for IRON.
from output to input. 2. In an audio-frequency or
feasibility study The procedures for evaluating
radio-frequency amplifier circuit, the reduction of
the potential gains in applying a computer sys-
feedback by electronic means.
tem to a job or to an organization™s process, or in
feedback bridge A bridge circuit in the feedback
modifying or replacing an existing system.
channel of an amplifier or oscillator.
FEB Abbreviation of FUNCTIONAL ELECTRONIC
feedback capacitance 1. A capacitance through
BLOCK.
which feedback current is coupled from the out-
Federal Communications Commission Abbrevia-
put to the input of a circuit or system. 2. The in-
tion, FCC. Established in 1934, the U.S. Govern-
terelectrode capacitance of a vacuum tube.
ment agency that regulates electronic com-
feedback control 1. The variable component (po-
munications. The FCC succeeded the Federal Ra-
tentiometer or variable capacitor) used to adjust
dio Commission (FRC), which was established in
the level of feedback current or voltage. 2. The
1927; the FRC succeeded the Radio Division of
control of circuit performance by means of feed-
the Bureau of Navigation in the Department of
back.
Commerce, whose jurisdiction over radio began
feedback cutter A device used for the purpose of
in 1912.
cutting grooves in phonograph disks. Feedback is
feed 1. To supply power or a signal to a circuit or
used to provide a flat frequency response.
device. 2. The method of supplying such a signal
feedback factor For a feedback amplifier, the
or power. See, for example, PARALLEL FEED and
quantity 1 “ bA, where A is the open-loop gain of
SERIES FEED. 3. To cause data to be entered
the amplifier and b is the FEEDBACK RATIO.
into a computer for processing.
278 feedback input current • feedthrough terminal


feedback input current In a feedback network, feedthrough capacitor A capacitor whose design
the current drawn by the feedback input. This is like that of a feedthrough terminal; it is
current affects the design parameters of a net- mounted in a hole in a chassis. The center screw
work. or wire is the “high” terminal of the capacitor, to
feedback loop The part of a circuit that provides which connections can be made above or below
controlled feedback in an operational-amplifier the chassis. The body of the device is the “low”
circuit. terminal of the capacitor; it is soldered to the
feedback oscillator A circuit in which oscillation chassis or secured with a nut.
is obtained by feeding a portion of the output of
an active amplifying device back to the input cir-
cuit by inductive coupling. Also called tickler os-
Chassis wall
cillator.
feedback path A path over which feedback, either
positive or negative, can occur in a circuit. The
feedback can be intentionally produced, or it can
Metal flange
be undesirable.
feedback percentage Symbol, n. In a feedback cir-
Center
cuit, the percentage of output voltage that is fed
conductor
back; n = 100Vf/Vo, where Vf is the feedback volt-
age and Vo is the open-loop output voltage. Com-
pare FEEDBACK RATIO.
feedback ratio For a feedback system, the ratio
Vf/Vo, where Vf is the voltage that is fed back
and Vo is the open-loop output voltage of the
system.
feedback rectifier See DIODE FEEDBACK RECTI-
FIER.
feedback regulator In a controlled-feedback cir-
cuit, the device that determines the amount of
feedthrough capacitor
feedback.
feedback resistance 1. The internal base resis-
tance of a point-contact transistor. 2. The resis- feedthrough component A passive device perma-
tance in a feedback loop. nently installed in a panel or plate (e.g., a
feedback transfer function The transfer function FEEDTHROUGH CAPACITOR or FEED-
of a feedback loop exclusively. THROUGH INSULATOR).
feedback winding A special winding on a magnetic feedthrough insulator An insulator mounted
amplifier or saturable reactor, for the introduc- tightly in a hole in a wall or chassis, and provided
tion of feedback currents. with a center hole for a lead.
feeder 1. A conductor or set of conductors that
carries electric power from one point to another.
2. The transmission line connecting a transmitter Panel or
to an antenna. chassis
feeder cable 1. A communication cable running in Nuts
a primary route from a central station (or in a sec-
ondary route from a main feeder cable) as a
means of making connections to distribution ca-
Threaded
bles. 2. In a cable television system, the cable
shaft
carrying transmission from the head end to the
trunk amplifier. Also called TRUNK CABLE.
Nuts
feeder loss Loss of energy resulting from resis-
tance in, or radiation from, feeder lines. Insulating
feeding In character recognition, a system in material
which documents go into the transport of a char-
acter reader at a steady, specified rate. feedthrough insulator
feed pitch The distance between feed holes.
feed reel The tape supply reel of a tape recorder.
feedthrough 1. The usually undesirable transmis- feedthrough terminal A terminal mounted tightly
sion of a signal through a circuit without being in a hole in a chassis or wall; it consists of a
processed by the circuit, because of unavoidable screw going through a feedthrough insulator.
capacitive coupling, for example. 2. Contraction Connections can be made to either end of the
of FEEDTHROUGH COMPONENT. screw.
279
FE-EL • ferrite limiter


FE-EL Abbreviation of ferroelectric-electrolumines- fermium Symbol, Fm. A radioactive metallic ele-
cent. ment that is artificially produced. Atomic num-
feeler 1. A wire or blade contact (e.g., a finger that ber, 100. Atomic weight, 257.
senses holes in a punched card). 2. The wire por- ferpic Acronym for ferroelectric ceramic picture de-
tion of a point-contact diode. vice. An image-storing device containing a photo-
Felici mutual-inductance balance An inductive conductive film, transparent electrodes, and a
null circuit for determining mutual inductance ferroelectric ceramic, in layers.
(Mx) in terms of a standard mutual inductance ferreed A form of magnetic switching device, simi-
(Ms). The secondary coils of two mutual-induc- lar to a reed relay, that maintains its position in-
tance circuits are connected in phase opposition. definitely without the need for a continuous
The standard mutual inductor, which is variable, current.
is adjusted for null. At null, Mx = Ms. ferret A vehicle or craft equipped for determining
the locations of enemy radar transmitters.
ferri- A prefix used to denote magnetic properties.
Mx ferric oxide Formula, Fe 2O3. A red oxide of iron
used to coat magnetic recording tape.
Null ferristor A high-frequency magnetic amplifier us-
Primary Secondary
detector ing a ferroresonant circuit.
Generator ferrite A high-resistance magnetic material con-
Secondary
sisting principally of ferric oxide and one or more
Ms other metals. After being powdered and sintered,
ferrites exhibit low eddy-current loss at high fre-
Primary quencies and make ideal core material for induc-
tors and switching elements. Also used in
television deflection yokes and in miniature an-
Felici mutual-inductance balance
tennas. Also see FERROSPINELS.
ferrite antenna See FERRITE-ROD ANTENNA.
ferrite bead 1. A magnetic storage device in the
female plug A plug whose contacts are separated
form of a bead of ferrite powder fused onto the
by a recess into which the prongs of a mating
signal conductors of a memory matrix. 2. A tiny
male plug are inserted. Compare HERMA-
ring of ferrite that can be slipped over a wire or
PHRODITE PLUG and MALE PLUG.
cable to choke off radio-frequency (RF) currents.
femto- Abbreviation, f. A prefix meaning quadril-
lionth (10“15).
femtoampere Abbreviation, fA. A unit of extremely
low current; 1 fA equals 10“15 A. Ferrite
femtofarad Abbreviation, fF. A unit of extremely bead
low capacitance; 1 fF equals 10“15 F.
femtovolt Abbreviation, fV. A unit of extremely low Cable
voltage; 1 fV equals 10“15 V.
fence A system or string of early warning radar
stations.
Fermat™s principle The principle that the path of a
ray of radiant energy between two points in any
medium is the shortest distance between those ferrite bead
points in that medium. This path is also the path
of least propagation time. This might not neces-
ferrite core A coil or switching-element core made
sarily be a straight line. On a flat plane, the path
from a ferrite; specifically, in a core memory, a
of least time between any two points is always a
small magnetic toroid that can retain its polarity
straight line, assuming constant velocity of prop-
when charged by a pulse.
agation. However, on a sphere, the path of least
ferrite core memory A magnetic memory in which
time between two points is represented by a great
ferrite cores are interconnected by a network of
circle.
input and output wires.
fermi Abbreviation, F. An extremely small unit of
ferrite isolator A microwave device that permits
length and wavelength, equal to one quadrillionth
(10“15) of a meter. energy to pass with negligible loss in one direction
through a waveguide or coaxial line, while absorb-
Fermi-Dirac distribution function The probabil-
ing energy passing in the opposite direction.
ity that an electron will be in a certain quantum
ferrite limiter A device used in the antenna circuit
state under conditions of thermal equilbrium.
or front end of a receiver, to prevent overload
This is determined as the probability that the
while maintaining a linear response. Used mostly
electron will be in a given energy band at a par-
at ultra-high and microwave frequencies.
ticular instant of time.
280 ferrite loopstick • fetch


ferrite loopstick See FERRITE-ROD ANTENNA. factor (selectivity attainable) can be extremely
ferrite memory A static memory using ferrite high. The core confines much of the magnetic
cores. See CORE MEMORY. flux within itself. When the coil current exceeds
ferrite-rod antenna Also called loopstick antenna. a certain level, core saturation occurs, and further
A small antenna that can be used for wireless re- increases in the current will not produce a cor-
ception at frequencies below approximately responding increase in magnetic flux. This de-
20 MHz. This antenna consists of a coil wound creases the effective inductance, and reduces the
on a solenoidal, high-permeability, powdered- efficiency because power is dissipated as heat in
iron core, usually less than 20 centimeters (cm) the core.
long and 1 cm in diameter. A series or parallel ferromagnetic material A substance that concen-
capacitor, in conjunction with the coil forms a trates magnetic lines of flux relative to their con-
tuned circuit. The operating frequency is deter- centration in free space. Iron, powdered iron, and
mined by the resonant frequency of the induc- ferrite are common examples.
tance-capacitance (LC) combination. Response ferromagnetic resonance The point at which the
is maximum off the sides of the coil, and a sharp permeability of a magnetic material peaks at a
null occurs off the ends. This antenna has nar- microwave frequency.
row bandwidth. The null can be oriented to min- ferromagnetic spinels Highly permeable and re-
imize system response to undesired local signals sistive ceramic-like materials. The low eddy-
or humanmade noise. Compare SMALL LOOP current losses and high permeability of these
ANTENNA. materials suit them for use as cores in radio-
ferrite switch A device that regulates the flow of frequency (RF) transformers and inductors. Also
power through a waveguide. The electric-field see FERRITE.
vector is rotated, resulting in a high degree of at- ferromagnetic tape Magnetic tape used for wind-
tenuation when actuated, but little or no attenu- ing closed transformer cores.
ation when not activated. ferrometer An instrument for testing hysteresis
ferroelectric 1. Producing ferroelectricity. 2. A fer- and permeability in steel and iron.
roelectric material. Ferron detector See IRON-PYRITES DETECTOR.
ferroelectric amplifier See DIELECTRIC AMPLI- ferroresonant circuit An inductance-capacitance
FIER. (LC) circuit in which the coil is a saturable reac-
ferroelectric capacitor A capacitor in which a fer- tor. Because of coil nonlinearity, the circuit is res-
roelectric material is the dielectric. onant at only one value of alternating-current (ac)
ferroelectric cell See FERROELECTRIC CAPACI- voltage, and exhibits both negative resistance
TOR. and bistable operation.
ferroelectric crystal A crystal of ferroelectric ma- ferroresonant counter A digital counter using fer-
terial. roresonant flip-flops, rather than semiconductor
ferroelectric flip-flop A flip-flop based on the hys- devices.
teresis of a ferroelectric capacitor. Compare FER- ferroresonant flip-flop A flip-flop using one or two
RORESONANT FLIP-FLOP. ferroresonant circuits instead of semiconductor
ferroelectricity Electric polarization in certain devices. See BISTABLE MULTIVIBRATOR. Com-
crystalline materials. The effect is analogous to pare FERROELECTRIC FLIP-FLOP.
the magnetization of a ferromagnetic material by ferroresonant shift register A shift register using
a magnetic field. ferroresonant circuits instead of semiconductor
ferroelectric-luminescent Pertaining to a ferro- devices.
electric cell that emits light. ferrosoferric oxide See MAGNETITE.
ferroelectric material A nonlinear dielectric mate- ferrospinels See FERROMAGNETIC SPINELS.
rial capable of producing ferroelectricity. Exam- ferrous Pertaining to a substance that contains
ples: barium titanate, barium strontium titanate, iron and is magnetizable.
potassium dihydrogen phosphate, guanadine Ferroxcube A nonmetallic ferromagnetic material
aluminum sulfate hexahydrate (GASH), Rochelle having high permeability and resistivity, and a
salt, and triglycene sulfate. Curie point near room temperature. These char-
ferromagnetic 1. Pertaining to a substance that acteristics make the material suitable for the
conducts a magnetic field with relative ease. 2. cores of radio-frequency (RF) inductors and
Pertaining to a material in which a magnetic-field transformers, and for high-frequency magnetic
change causes a voltage, which in turn results in shields.
a measurable current flow. Fessenden oscillator In underwater communica-
ferromagnetic-core inductor A coil of wire de- tions, a transmitter of acoustic waves.
signed to introduce inductive reactance into a cir- FET Abbreviation of FIELD-EFFECT TRANSISTOR.
cuit or system, wound around a core consisting of fetch An operation in a computer run in which the
ferromagnetic material that greatly increases the location of the next instruction is taken from
inductance for a given number of turns. With memory and changed if necessary; it then goes to
proper design and choice of core material, the Q the control register.
281
FET current meter • field coil


FET current meter An ammeter, milliammeter, or fiberoptics 1. Also called optical fibers. Extruded
microammeter having a self-contained amplifier materials, such as certain plastic filaments, that
that uses field-effect transistors. Also see ELEC- provide paths for light. 2. The science of develop-
TRONIC CURRENT METER. ing and using communications systems that use
FET op-amp 1. An operational amplifier composed optical fibers to transfer data.
of field-effect transistors and associated compo-
nents. 2. An operational amplifier having a field-
effect transistor in its input stage.
FET voltmeter A voltmeter using a field-effect
transistor amplifier for high-impedance input.
Also see ELECTRONIC VOLTMETER.

Fiber

Reflection
point
Reflection
point




Light
beam

fiberoptics

FET VOM A volt-ohm-milliammeter (VOM) using a
field-effect transistor amplifier for increased sen- fiberoptic scrambler A fiberscope in which a cen-
sitivity and high input impedance. ter section of fibers in the core is deliberately dis-
FF Abbreviation of FLIP-FLOP. oriented before the bundle is encapsulated; when
fF Abbreviation of FEMTOFARAD. cut, one half can decode the image encoded by
FFI Abbreviation of FUEL-FLOW INDICATOR. the other half. See FIBERSCOPE.
fhp Abbreviation of FRACTIONAL HORSEPOWER. fiberscope A flexible bundle of optical fibers having
fiber 1. A tough, vulcanized insulating material. a lens at each end; it is used to view areas that
Dielectric constant, 2.5 to 5. Dielectric strength, are otherwise inaccessible to view.
2 kV/mm. 2. A thin thread of a material. 3. Also fiber stylus See FIBER NEEDLE.
called optical fiber. A light-conductive transpar- fibre Alternate (Brit.) spelling of FIBER.
ent filament; see FIBEROPTICS, 1. fibrillation Dangerous, irregular beating of the
fiber electrometer An instrument for measuring heart that often follows electric shock. Also see
small quantities of electricity. It consists of a CARDIAC STIMULATOR and DEFIBRILLATION.
thin thread, such as one of plasticized quartz, fidelity The degree to which a circuit or device
hanging freely between two knife-edged metal transmits a signal without distorting it. Pertains
pieces that are charged by the electricity being especially to acoustic devices and stereo audio
measured. The charge draws the fiber away from equipment.
its position of rest. The movement can be ob- field 1. A volume of space in which a force is oper-
served with a microscope. A special form of this ative. See, for example, ELECTRIC FIELD and
instrument, using two fibers, is the bifilar elec- MAGNETIC FIELD. 2. Half of a video image, con-
trometer. sisting either of all the even-numbered lines, or
fiber needle A soft phonograph needle made from all the odd-numbered lines. 3. A computer record
a fiber. It produces less disk wear than other subdivision containing an information unit (e.g.,
styli, but is short-lived. a bank account record might have deposits as a
fiber metallurgy A process in which metallic fibers field).
or filaments are grown. field circuit breaker A circuit breaker designed to
fiberoptic bundle A cable of optical fibers. See control the field excitation of a motor or other de-
FIBEROPTICS, 1. vice.
fiberoptic coupling Also called optical coupling. A field coil 1. The winding on the field pole of a mo-
method of coupling in which a light-conducting tor or generator. 2. The winding on the pole of an
fiber is placed between a light (signal) source and electrodynamic speaker. 3. The main coil of a re-
a photoreceptor. Also see FIBEROPTICS, 1, 2. lay. 4. The fixed coil in an electrodynamometer.
282 Field Day • fil


Field Day In amateur radio, an annual contest field magnet 1. The permanent magnet in a dy-
sponsored by the American Radio Relay League namic speaker. 2. A similar magnet in an ear-
(ARRL) to simulate emergency communication phone, generator, microphone, motor, phono
conditions. It occurs during the last full weekend pickup, transducer, etc.
in June. field pickup 1. A probe or sensor for insertion into
field direction The direction in which an electric an electric or magnetic field. 2. An on-location ra-
field or magnetic field exerts its force. dio or television program (i.e., one coming from
field effect The phenomenon in which the flow of outside the studio). Also called remote or NEMO.
current carriers in a solid substance is controlled field resistor A resistive component consisting of
by an external electric field. A useful application an insulated form with a thin layer of conductive
is the FIELD-EFFECT TRANSISTOR (FET). material.
field-effect tetrode Also called dual-gate FET. A field rheostat The rheostat whose setting deter-
field-effect transistor (FET) in which the gate elec- mines the amount of current flow through the
trode is split into two parts, each connected to a field coil of a motor or generator.
separate external lead. The reverse bias between field scan A form of television scanning in which
the channel and either gate lead affects the con- the lines are scanned alternately.
ductivity through the device. field-sequential system A color-television system
field-effect transistor Abbreviation, FET. A mon- in which the image is reproduced by means of pri-
olithic semiconductor amplifying device in which mary color fields (red, green, and blue) flashed se-
a high-impedance GATE electrode controls the quentially on the screen of the picture tube.
flow of current carriers through a thin bar of sili- Compare DOT-SEQUENTIAL SYSTEM and LINE-
con (rarely, germanium) called the CHANNEL. SEQUENTIAL SYSTEM.
Ohmic connections made to the ends of the chan- field strength See FIELD INTENSITY.
nel constitute SOURCE and DRAIN electrodes. field-strength meter An instrument for measur-
Also see JUNCTION FIELD-EFFECT TRAN- ing the radio-frequency (RF) voltage of a signal
SISTOR, METAL-OXIDE SEMICONDUCTOR reaching a chosen location. The instrument con-
FIELD-EFFECT TRANSISTOR, and CHANNEL sists essentially of a radio detector equipped with
JUNCTION FIELD-EFFECT TRANSISTOR. a portable antenna and an output meter.
field-effect varistor A nonlinear dual-terminal
semiconductor device capable of maintaining a
value of current for a range of voltages.
field-emission microscope An instrument for ex-
amining the atomic structure of high-melting-
µA
point metals; it magnifies more than 2 million
times. The metal to be examined is made into a
needle that is subjected to 5 to 30 kV; electrons
emitted by the tip of the needle form an image on
a fluorescent screen.
field forcing A method of controlling a motor by
changing the magnetic field in the windings. field-strength meter
field frequency In television, the product of frame
frequency and fields per frame (in the United
States, 60 per second). field telephone A rugged, portable telephone sys-
field intensity 1. The strength of an electric or tem for outdoor use.
magnetic field. 2. The strength of an electromag- field test A test of equipment under actual operat-
netic field, usually expressed in microvolts per ing conditions (i.e., outside the laboratory or fac-
meter or millivolts per meter. tory).
field-intensity meter See FIELD-STRENGTH ME- field winding See FIELD COIL, 1, 2.
TER. fig. Abbreviation of figure (usually in reference to
field ionization The tendency for atoms to be ion- an illustration).
ized in a gas by a high-intensity electric field. The figure-8 pattern 1. A bidirectional antenna pat-
ionization occurs mostly near the poles of the tern whose cross section, in a specified plane, re-
electric field. sembles the numeral 8. 2. A Lissajous figure
field-ion microscope A high-resolution field-emis- resembling the numeral 8.
sion microscope that uses helium ions instead of figure of merit 1. For a capacitor, inductor, or
electrons. The ions are repelled by the tip of the tuned circuit, the ratio of reactance to resistance.
metal needle under observation, forming an im- Also called Q factor or Q. 2. For a magnetic am-
age on a fluorescent screen. Also see FIELD- plifier, the ratio of power amplification to control
EMISSION MICROSCOPE. time constant. 3. For a transistor, the gain-band-
field length Record field size in applicable units, width factor.
usually bytes, characters, or words. fil Abbreviation of FILAMENT.
283
filament • filler


filament In a vacuum tube or incandescent lamp, file layout How the contents of a file are organized;
the thin wire heated by electric current; it emits usually defined by the system or specified by a
electrons, light, and heat. The filament is the program.
cathode in a filament-type tube, but serves only file maintenance To delete, add, or correct records
to heat indirectly the cathode sleeve in an indi- in a file. Unlike updating, which is done to reflect
rectly heated tube. changes in events recorded in the file, mainte-
filament battery See A BATTERY. nance ensures that the contents of the file are ac-
filament choke A radio-frequency (RF) choke op- curate records of the necessary data.
erated in the filament lead of an electron tube. file management A method of storing and recall-
Such chokes are necessary in filament-type tubes ing data from computer storage media, such as
in RF power amplifiers. magnetic disks.
filament circuit The circuit carrying filament cur- filename In a computer file label, the alphanu-
rent. meric character set that identifies and describes
filament coil See FILAMENT WINDING. the file. It generally consists of one to eight char-
filament current Symbol, IF. The current flowing acters, often including an extension of one to
through the filament of a vacuum tube. three characters. In some computer operating
filament emission Electrons emitted directly by systems, filenames can be much longer (e.g., up
the filament in an electron tube (thermionic emis- to 32 characters). See FILENAME EXTENSION.
sion) or the amount of such emission. filename extension A group of one, two, or three
filament hum A hum signal caused by voltage in- characters following the main body of a FILE-
duced in a circuit by the alternating-current (ac)- NAME, and separated from it by a period (.). It
operated filaments (heaters) of tubes or by the generally denotes the application or purpose of
filament wiring. the file. The extension .BAK, for example, denotes
filament lag The time delay in the heating and a backup file; .TXT denotes a text file; .BMP de-
cooling of an ac tube or lamp filament as fila- notes a bit-mapped graphics file.
ment-current changes polarity. file organization The way words, bits, or records
filament power supply A source of power, usually are physically arranged in the storage medium for
alternating-current, for heating the filament of a a file, possibly including the method of access (se-
vacuum tube or tubes. rial, alphabetical, random, etc.).
filament resistance 1. The resistance of the fil- file-oriented programming Computer program-
ament in an electron tube or incandescent ming that uses a general file and record-control
lamp. 2. The resistance of an external dropping program to simplify I/O coding.
resistor in the filament circuit of a tube or file-oriented system A system having file storage
lamp. as its basis.
filament transformer A step-down transformer file print A hard copy (printout) of the contents of
that supplies power exclusively to the filament a file.
(heater) of an electron tube. file processing The operations associated with
filament-type bolometer A BOLOMETER in making and using files.
which the sensitive element is a wire filament. file protection Preventing the possibility of writing
Examples: barretter, incandescent lamp, and over data files before they are made available for
wire fuse. use. It is usually done by having a program check
filament voltage Symbol, VF. The voltage across file labels.
the filament of an electron tube. file reconstitution Restoring a partially or com-
filament winding In a power transformer, the coil pletely damaged file by updating a previous gener-
that supplies heating power to the filament of a ation of the file using a file of interim transactions.
vacuum tube. Also called FILAMENT COIL. file recovery Following the interruption of file pro-
file An organized collection of records related by a cessing because of system failure, the procedure
common format, data source, or application. for reestablishing the file™s condition as necessary
file conversion Converting data files from one for the resumption of processing without losing
form to another, often for the purpose of making accuracy.
them compatible with other computers. file section Part of a file in certain consecutive lo-
file gap An area of a data medium that signifies the cations on a storage medium.
end of a file; it can also mark the start of another file security Protective and security measures
file. (e.g., the issuance of clearances, status markers,
file identification A code that identifies a file. etc.) as they relate to computer files.
file label File identification in which the first file set A collection of interrelated files stored con-
record in the file is a set of characters unique to secutively in a magnetic disk volume (package).
the file; it conveys such information about (for ex- fill The percentage of lines in a cable that are actu-
ample, a tape file as a description of content, gen- ally in use at a given time.
eration number, reel number, date of writing, filler A nonessential data part used, for example,
etc.). Also called HEADER LABEL. to bring a record to a standard size.
284 film • filter stopband


film See THIN-FILM MEMORY. blocking currents at other frequencies. Exam-
film capacitor A capacitor in which the electrodes ples: BANDPASS FILTER, BAND-REJECTION
are plated or deposited on the faces of a thin film FILTER, HIGH-PASS FILTER, and LOW-PASS
of plastic or other dielectric material. FILTER. 2. An inductance-capacitance (LC) or
film chain A system designed for the transmission resistance-capacitance (RC) circuit for removing
of movies over a television system. This requires the ripple from the output of a power-supply rec-
synchronization of the movie frame rate with the tifier. 3. A transparent disk with special optical
television scanning rate. properties placed in front of a camera lens for a
film frame A single picture on a strip of motion special photographic effect. 4. A character pat-
picture film. terned to control the elimination or selection of
film-frame blanking interval The interval during characters in another pattern. 5. A device or pro-
which a film frame is blanked out as motion- gram that separates information, according to
picture film moves through a camera, projector, certain specifications or characteristics. 6. A ma-
or pickup. The blanking action allows a frame to chine word that specifies the elements to be
move into position without blurring the image as treated in another machine word; also called
seen by viewers. MASK.
film integrated circuit A monolithic circuit whose filter attenuation In a selective filter, the power,
elements are films formed on an insulating sub- current, or voltage loss, in decibels, that occurs
strate. within the passband.
film pickup A photocell, photodiode, or phototran- filter attenuation band In a selective filter, the
sistor circuit used to pick up recordings from the frequency band(s) outside the passband; that is,
sound track of motion-picture film. the frequency range over which signals are signif-
film reader A device for converting data on film icantly attenuated.
into digital form for a computer. filter bank In audio applications, a set of band-
film recorder An apparatus that records data as a pass filters, each of which covers a specific por-
sound pattern on film. Compare FILM REPRO- tion of the audio-frequency (AF) spectrum. There
DUCER. is some (minimal) overlap between the passbands
film reproducer An apparatus that plays back of the filters, so an AF signal of a specific fre-
data recorded on photographic film. Compare quency will always pass through at least one of
FILM RECORDER. the filters, but will never pass through more than
film resistor Also called carbon-film resistor or two of the filters.
metal-film resistor. An electronic component con- filter capacitor A capacitor that provides capaci-
sisting of a mixture of ceramic, carbon, and/or tive reactance in a wave filter or power-supply fil-
metal, applied to a cylindrical form in a thin layer ter while also blocking direct current.
to obtain a desired value of resistance. The cylin- filter center A place where information is modified
drical form is made of an insulating substance, for transmission to aircraft pilots. Such informa-
such as porcelain. The film can be deposited on tion can include weather data, course changes, or
this form by various methods, and the value tai- other instructions.
lored as desired. Metal-film units can be made to filter choke An inductor that provides inductive
have nearly exact values. Film type resistors usu- reactance in a wave filter or power-supply filter
ally have low to medium-high resistance. A major while affording relatively easy conduction of di-
advantage of film-type resistors is that they, like rect current.
carbon-composition units, do not have much in- filter crystal A piezoelectric crystal used in a
ductance or capacitance. A disadvantage, in CRYSTAL RESONATOR.
some applications, is that they cannot handle as filter cutoff The frequency or frequencies at which
much power as the more massive carbon-compo- the transmission figure of a filter is below its
sition units, or as wirewound types. Compare maximum value by a prescribed amount, usually
CARBON-COMPOSITION RESISTOR, WIRE- 3 dB, representing the half-power point(s).
WOUND RESISTOR. filter discrimination The amount of fluctuation in
film scanning The conversion of a movie into a the insertion loss of a bandpass, band-rejection,
form suitable for transmission by television. high-pass, or low-pass selective filter. The fluctu-
film speed 1. The speed at which motion-picture ation is measured at various points in the filter
film moves intermittently through a camera, pro- passband.
jector, or pickup, measured in feet or frames per filter inductor See FILTER CHOKE.
second. 2. A measure of film™s light sensitivity, filter passband The frequency range over which a
given as an ASA (American Standards Associa- selective filter passes signals with minimum at-
tion) or DIN (European) number; in either system, tenuation.
the higher the number, the greater the light sen- filter reactor See FILTER CHOKE.
sitivity. filter slot In a waveguide, a slot that acts as a
filter 1. A circuit or device that passes alternating choke to suppress undesirable modes.
currents at some frequencies while attenuating or filter stopband See FILTER ATTENUATION BAND.
285
filter transmission band • firing angle


filter transmission band See FILTER PASSBAND. correct position. It uses machine vision, tactile
fin 1. A metal disk or plate attached to a compo- sensors, pressure sensors, or high-precision dis-
nent for the purpose of radiating heat. 2. A pro- placement transducers.
jection in an irregular heatsink. finger See FEELER, 1.
final amplifier Also called output amplifier or finger plethysmograph A device that senses and
power amplifier. In a wireless transmitter, the records the resistance through the human finger
amplifier that boosts the signal power to the level during various parts of the heart cycle.
to be emitted over the airwaves. The input is finger rules See FLEMING™S LEFT-HAND RULE,
provided by the driver; the output is connected to FLEMING™S RIGHT-HAND RULE, and RIGHT-
the system, to a transverter, or to a network cable HAND RULE FOR WIRE.
power amplifier. In some transmitters, the finish lead The lead attached to the last turn of a
output amplifier requires no tuning; in others, coil. Also called outside lead. Compare START
adjustment of the output circuitry is necessary to LEAD.
obtain proper coupling to the antenna system. In finished blank The end product in the crystal man-
a single-sideband (SSB) or amplitude-modulated ufacturing process, often including electrodes.
(AM) transmitter, all amplifiers following the finishing The careful handwork and testing in-
modulator must be linear. In transmitters in- volved in bringing a crystal blank to a condition
tended for use only in digital modes or for fre- that is acceptable as finished, according to speci-
quency modulation (FM), power amplifiers need fications.
not be linear. finishing rate The rate of charging a battery, as
final result A result displayed at the end of a data the battery approaches a full charge. Generally,
processing operation. Compare INTERMEDIATE the finishing rate is less than the normal charg-
RESULT. ing rate.
finder The switch or group of relays that selects finite Pertaining to that which has defined limits.
the path for a call going through a telephone finite sample space In statistics, a sample space
switching system. Also called LINE FINDER. having definite limits.
fine adjustment Adjustment of a quantity in small finite series A mathematical series having a lim-
increments or as a smooth, continuous variation. ited number of terms. Example: 1 + 0.1 + 0.01 +
Compare COARSE ADJUSTMENT. 0.001, a finite series containing four terms and
fine-chrominance primary See I SIGNAL. whose sum is equal to 1.111.
fine frequency control A variable component, finned surface The irregular surface of a heatsink.
such as a potentiometer or variable capacitor, The ratio of surface area to volume is greater than
that permits a signal or response frequency to be with a flat surface; this increases the cooling ef-
varied over a small increment; it is often used in fectiveness of the heatsink.
conjunction with a coarse frequency control. fins Metal vanes radiating from components that
dissipate large amounts of power as heat.
FIR Abbreviation of FAR INFRARED.
Coarse
fire A transition from non-conduction to conduc-
control
tion in an ionizing switching device.
To
fire control The aiming and firing of guns auto-
osc.
Fine
matically via radar and associated electronic sys-
control
tems.
firefighter robot A robotic device or system in-
tended to protect lives and property from fire.
365
10
Such a robot can be simple, such as an auto-
pF
pF
matic sprinkler system actuated via heat sensors
and/or smoke detectors. More sophisticated sys-
tems might use autonomous or remotely con-
trolled androids that perform the same functions
as human firefighters.
Fire Underwriter™s regulations See NATIONAL
fine frequency control
ELECTRIC CODE.
firing The pulse that initiates conduction in an
ionization switching device.
fine-groove record See MICROGROOVE REC-
firing angle 1. For a magnetic amplifier, the angu-
ORD.
lar distance through which the input-voltage
fine index In computer operations, a secondary,
vector rotates before the core is driven into
supplemental index used with a main, or gross,
saturation. 2. For a silicon-controlled rectifier
index when the latter does not adequately detail
(SCR), the point, as an angle (in degrees or
the differences between the items being indexed.
radians), along the control voltage half-cycle at
fine-motion planning The scheme used by a
which the SCR fires.
robotic end effector (“hand”) to get in exactly the
286 firing circuit • fixed-frequency oscillator


Collector antennas
firing circuit Any circuit, such as a phase shifter,
that permits adjustment of the firing angle of a
Terminating
silicon-controlled rectifier (SCR) or similar device,
resistor
or which delivers the required pulse or other sig-
nal to initiate firing.
firmware 1. Programs (software) in nonvolatile Transmission line To receiver
computer memory [e.g., in a read-only memory
(ROM), that can only be changed by replacement
with an alternate unit]. 2. Unalterable internal
interconnections that determine what a comput-
ing device or system can do. Also called MICRO-
PROGRAM. fishbone antenna
first detector In a superheterodyne circuit, the
signal frequency detector. Compare SECOND DE-
TECTOR. five-element code A five-impulse telegraph code
first filter capacitor The input capacitor in a ca- that describes a character (e.g., Baudot, which
pacitor-input power-supply filter. also includes start and stop elements).
first Fresnel region A portion of a directional five-layer device A semiconductor device contain-




Y
transmitted electromagnetic ray, shaped gener- ing four pn junctions. Examples: diac and triac.
ally like a paraboloid with the apex at the trans- five-level code A teletype code that utilizes five bi-




FL
mitter and the axis in the direction of nary elements to define a character.
transmission. Any point in the first Fresnel zone fix 1. In direction finding, the point at which two
is in such a position that the sum of the lengths lines of direction intersect. 2. In electronics main-
of the paths from the point to the receiver, and tenance, to repair successfully. 3. To subject an
AM
the point to the transmitter, is no greater than in-process circuit board to a solution or other
0.5 wavelength more than the distance from the medium to stop a photographic action perma-
transmitter to receiver. nently. Also, the solution in which such photo-
first harmonic The fundamental frequency in a sensitive materials can be immersed to halt
complex waveform from which multiples are gen- development.
TE

erated. fixed bias Bias voltage or current supplied from a
first-in/first-out Acronym, FIFO. A read-write fixed external source (such as a battery or power
memory commonly used as a buffer to smooth supply) independent of the operation of the bi-
out the flow of data bits in a digital system. The ased device. Compare AUTOMATIC BIAS.
output bits are in the same order (sequence) as fixed block length Blocks of data having a fixed
the input bits. If a data bit x goes into the FIFO number of words or characters, as required be-
before data bit y, then x will always emerge from cause of hardware limitations or a program in-
the FIFO before y. Compare PUSHDOWN STACK. struction. Compare VARIABLE BLOCK LENGTH.
first-in/last-out See PUSHDOWN STACK. fixed capacitor A nonadjustable capacitor (i.e.,
first law of thermodynamics Quantities of heat one having a single unalterable value).
can be converted into mechanical work, and vice fixed component Any component (e.g., a capaci-
versa. Also see MECHANICAL EQUIVALENT OF tor, inductor, or resistor that has one unalterable
HEAT. value).
first level address See ABSOLUTE ADDRESS. fixed contact The stationary contact in a relay or
first selector The selector that responds to the switch. Compare MOVABLE CONTACT.
first-digit dial pulses when a telephone number is fixed-crystal detector A simple crystal detector in
called. which the point of the contact wire is perma-
fishbone antenna An untuned, wideband direc- nently placed in contact with a sensitive spot on
tional antenna of the general end-fire type. Con- the surface of the crystal.
sists of a number of collector antennas, each fixed field Fields in records organized so that
capacitively coupled to the resistor-terminated those containing similar information in each
transmission line in collinear pairs. It is so record are the same length and in the same rela-
called from its resemblance to the skeleton of a tive position in the record. Compare VARIABLE
fish. FIELD.
fishpaper A chemically treated, vulcanized-fiber fixed form coding The coding of source languages
paper used for electrical insulation. so that each part of the instruction is in a fixed
fish pole A microphone boom that can be held in field.
the hand. fixed-frequency amplifier An amplifier that is
fist In radiotelegraphy and wire telegraphy, an op- pretuned to operate on one frequency, or in a rel-
erator™s manual sending style. atively narrow band of frequencies.
fitting A device intended to mechanically fasten a fixed-frequency oscillator An oscillator that is
wire or cable in place. preset to operate on one frequency. Such an os-




Team-Fly®
287
fixed-frequency oscillator • flange


cillator can be self-excited or controlled (crystal, 4. An indicator identifying the members of mixed
fork, magnetostriction, etc.). sets. 5. A character that signals the presence of
fixed-frequency receiver A receiver that is pre- some condition (e.g., an error flag indicates that a
tuned to receive signals of one frequency. data item caused an error).
fixed-frequency transmitter A transmitter that is flag event A program condition that causes a flag
pretuned to radiate signals of one frequency. to be set.
Such a transmitter can contain a self-excited or flag line An input pulse to a microprocessor that
crystal-controlled oscillator. depends on specific external instructions. Indi-
fixed inductor A nonadjustable inductor (i.e., one cates a certain condition or change of state.
having an unalterable value of inductance). flagpole antenna 1. Any of several vertical UHF or
fixed-length record A record in which word or VHF antennas consisting of a radiator mounted
character size is constant. Compare VARIABLE atop a coaxial pipe or cable (see, for example,
LENGTH RECORD. COAXIAL ANTENNA). It takes its name from its
fixed logic Applicable to computers or peripherals resemblance to a flagpole. 2. A vertical antenna
whose logic can only be altered internally by formed by shunt-feeding a pole already in exis-
changing connections. tence, such as a flagpole. This can be done to
fixed memory A nonvolatile readout computer conceal the antenna.
memory that can only be altered mechanically.
fixed placement file A file that has been allocated
a fixed location in storage.
Whip to coax
fixed-point system A notation system in which a
center conductor
single set of digits represents a number, and the
radix point (in the decimal system, the decimal Center
point) can only be placed in one position for the insulator
value being expressed. Also see FLOATING-
Pipe to coax
POINT CALCULATION.
outer conductor
fixed resistor A nonadjustable resistor (i.e., one
having an unalterable value of resistance).
fixed-sequence robot A robot that performs one
task or set of tasks, making exactly the same
Base
movements every time. The sequence is pro-
Coaxial insulator
grammed in the robot controller via firmware.
feed line
Many assembly robots and toy robots are of this
type. Compare FLEXIBLE AUTOMATION.
fixed station A radio station operating from a sta-
tionary point; one that is not mobile.
fixed-step potentiometer A potentiometer whose flagpole antenna, 1
output is varied in one or more discrete steps by
fixed-resistor sections. Also see POTENTIOME-
TER. flag terminal A form of terminal that does not re-
fixed wireless 1. A cellular communications net- quire soldering for electrical contact. A protrud-
work in which some, or all, of the end users are at ing “flag” is crimped around the conductor.
fixed locations. This is increasingly popular as an flame alarm A (usually photoelectric or thermo-
alternative to conventional hard-wired telephone electric) device or circuit for detecting a flame and
and Internet access. 2. The use of wireless equip- actuating an alarm.
ment, such as cell phones and wireless- flame control A (usually photoelectric or thermo-
modem“equipped computers, at fixed (rather electric) device or circuit for sensing and auto-
than mobile or portable) locations. matically controlling the height of a flame, such
fixed word length Applicable to the organization of as a gas pilot.
information in storage in which each computer flame-failure control A FLAME CONTROL that au-
word stored has a fixed number of characters or tomatically cuts off the fuel if the flame goes out.
bits. flame microphone A microphone in which two
fixture A piece of hardware used in equipment set- electrodes in a flame undergo a change in electri-
ups (e.g., microwave couplers, joints, sections, cal resistance when the flame is influenced by
etc.). sound waves, thus modulating current passing
fL Abbreviation of FOOT-LAMBERT. between the electrodes.
flag 1. A piece of information added to a data item flange 1. A flat, protruding edge used for fastening
that gives information about the data item. 2. A a connector or plug to the chassis of a piece of
bit added to a character or word to delineate a equipment. 2. In a waveguide, a coupling used for
field boundary. 3. An indication that an operation connection to another section of waveguide, or to
is complete and need not be done by the program. a horn or other external device.
288 flange focus • flattening


flange focus The focal length of a lens, based on of an electromechanical hard drive. This type of
the distance from the mounting flange to the focal memory allows a computer to store, access, and
plane. run large data files or programs much faster than
flanging In sound systems, a means of obtaining is possible with a conventional hard drive. See
special effects using a COMB FILTER. Creates an also NONVOLATILE MEMORY, RANDOM-
“extraterrestrial,” digitized sound. Commonly ACCESS MEMORY.
used by rock music bands. flashover The sudden discharge of electrical en-
flanking Modification of the response of a selective ergy between electrodes or conductors, often ac-
filter, resulting from the parallel connection of companied by light; it is usually the result of
two or more similar filters. excessive voltage.
flap See DROP INDICATOR. flashover voltage 1. The peak voltage at which
flap attenuator A waveguide attenuator consisting FLASHOVER occurs. 2. The voltage at which dis-
of a sheet of resistance material inserted trans- ruptive discharge occurs between electrodes and
versely into the waveguide through a slot. across the surface of an insulating material.
flare 1. The hyperbolic cross section of a horn an- flash plating Electroplating in which a thin layer is
tenna or loudspeaker. 2. A transient or stationary deposited quickly.
bright area with (usually) a central pip on the flash test Insulation testing by applying a higher-
screen of an otherwise blank oscilloscope or tele- than-normal voltage for a short time.
vision picture tube. flashtube A straight or coiled glass tube filled with
flare angle The gradual change in a waveguide™s gas and provided with electrodes. When a high
diameter over its length. voltage is applied to the electrodes, the tube emits
flare factor The angle at which the faces of a horn a brilliant flash of light.
speaker are curved or turned outward. flat cable Also called ribbon cable. A cable whose
flaring constant Symbol, m. A number express- flexible conductors are molded side by side in a
ing the degree of flare (see FLARE, 1) in a horn flexible, flat ribbon of plastic (such as polyeth-
antenna or loudspeaker. The value of m is equal ylene).
to 0.6931/d, where d is the distance along the flat-compounded generator A compound-wound
axis required for the cross-sectional area A of generator whose windings are proportioned so that
the horn to double. If d is given in feet (ft), for ex- the full-load and no-load voltages are identical.
ample, then A is in units of square feet (ft2) and flat fading Fading of a radio signal that occurs in-
m is in units of reciprocal feet (1/ft). If d is in dependently of frequency; all frequency compo-
centimeters (cm), then A is in units of square nents of the signal fade to the same extent at the
centimeters (cm2) and m is in units of reciprocal same time.
centimeters (1/cm). flat file A computer file containing unfolded docu-
flash 1. A photographic camera flash. 2. To vapor- ments.
ize a metal (such as magnesium) in an electron flat frequency response Relatively equal response
tube being evacuated, to absorb gases. 3. to all fixed-point frequencies within a given spec-
Flashover. trum, exhibited by an amplifier or other circuit
flash arc In a vacuum tube, a sudden high-current that must transmit a band of frequencies.
arc between cathode and plate at high plate volt- flat line A transmission line in which there are no
ages; it can short-circuit the plate power supply. standing waves, or for which the standing-wave
flashback voltage The maximum inverse voltage ratio is very low.
that causes the gas in a tube to ionize. flat pack An integrated circuit package consisting
flash delay A device that automatically postpones of a square or rectangular flat housing, with pins
the operation of a FLASHTUBE until a predeter- projecting straight outward from the edges.
mined instant, such as the moment when a mov- flat response A response characteristic in which
ing object arrives at a particular point before a the dependent variable is substantially constant
camera. over a specified range of values of the indepen-
flasher An electrical or electronic device or circuit dent variable. For example, in amplifier opera-
that flashes a light or a series of lights sequen- tion, an output signal whose component
tially. fundamental frequencies and their harmonics are
flasher LED A light-emitting diode (LED) that, in the same proportion as those of the input sig-
when connected to a low-voltage direct-current nal being amplified.
(dc) source, emits light that flashes at a basic rate flat-ribbon line A transmission line (feeder) con-
of a few pulses per second. sisting of two flexible conductors molded in a flex-
flashlamp 1. See FLASHTUBE. 2. A small portable ible, flat ribbon of plastic, such as polyethylene.
light operated from self-contained cells; a flash- Also called twinlead.
light or lantern. flattening The leveling-off or blunting of a nor-
flashlight See FLASHLAMP, 2. mally peaked or curved response, often caused by
flash memory High-capacity, nonvolatile random- signal saturation within a circuit. Sine-wave clip-
access memory, used in some computers in place ping is an example.
289
flat top • flight telerobotic servicer


flat top 1. The horizontal radiating portion of an flexible automation The ability of a robot or sys-
antenna. 2. See FLAT-TOP ANTENNA. 3. Of an tem to do various different tasks. Changing from
amplifier, to distort by clipping of the positive one task to another is simply a matter of chang-
half-cycles. ing software. Compare FIXED-SEQUENCE
flat-top antenna An antenna having a horizontal ROBOT.
wire or wires at the top to lower the resonant fre- flexible collodion A viscous solution of pyroxylin
quency and increase the bandwidth. (cellulose nitrates) used sometimes as a binder
flat-top beam A bidirectional, end-fire antenna for coils.
consisting of two close-spaced dipoles center-fed flexible contact A contact made from flat, metal
out of phase. Also see KRAUS ANTENNA. spring stock; it is usually bent or curved. Also
flat-topping The positive-peak clipping of a modu- called spring contact.
lation envelope that occurs when an amplifier is flexible coupling A device for joining two shafts
overdriven or when a signal is overmodulated. and conveying rotary motion from one to the
This is in contrast to deliberate clipping. Flat- other; it is elastic, so the shafts need not be ex-
topping results in “splatter” and is, therefore, an actly aligned with each other.
undesirable characteristic in an amplitude- flexible flat cable See FLAT CABLE.
modulated signal. flexible manufacturing system A roboticized
flat-top response The ability to uniformly transmit manufacturing plant that can turn out a variety
frequencies in a given band. of different products. One or more central com-
flat transmission line 1. A transmission line that is puters oversee the operation of the facility. Such
free of standing waves. Also see MATCHED factories are commonly used in the production of
TRANSMISSION LINE. 2. See FLAT-RIBBON LINE. electronic devices (such as printed circuits, cal-
flaw An irregularity in a substance that can result culators, and portable radios).
in problems, such as mechanical failure or poor flexible resistor An insulated, wirewound resistor
equipment performance. that can be bent, coiled, or knotted.
flaw detector An instrument that uses ultrasonic flexible shaft A control shaft that can be bent
waves to detect internal flaws in metal. The waves somewhat while still allowing easy adjustment.
are reflected by flaws. flex life A measure of how much bending a con-
F layer See F REGION. ductor or other flexible object can take without
fLb Abbreviation of FOOT-LAMBERT. breaking.
Fleming/Kennelly law Under conditions at or flexode A diode that is flexible in that its junction
near magnetic saturation in a ferromagnetic sub- can be changed (i.e., reversed without reversing
stance, the reluctivity is directly proportional to its leads, its resistance being variable from the
the intensity of the magnetic field. forward- to backward-resistance value).
Fleming™s generator rule See FLEMING™S RIGHT- flicker 1. A tendency for a video image to appear,
HAND RULE. disappear, and reappear, or to increase and de-
Fleming™s left-hand rule A simple way of indicat- crease in intensity frequently. 2. The effect cre-
ing certain relationships in the behavior of elec- ated by such action (as in a flickering light).
tric generators and motors. If the thumb, index flicker frequency The number of times the screen
finger, and middle finger of the left hand are posi- illumination flashes on and off in the projection of
tioned so that they are at right angles to each a motion picture. It is 48 per second (twice the
other, the thumb will point in the direction of frame rate) in conventional movie projectors; for
force or motion when the index finger is pointed each frame, the screen is blanked once when the
in the direction of flux; the middle finger points in frame is pulled into position and once again dur-
the direction of current flow. Compare FLEM- ing projection of the frame.
ING™S RIGHT-HAND RULE. flight control Electronic monitoring and control of
Fleming™s motor rule See FLEMING™S LEFT- an aircraft in flight.
HAND RULE. flight path The course planned for an aircraft™s
Fleming™s right-hand rule A simple way of indi- flight.
cating certain relationships in the behavior of flight-path computer A computer that controls
electric generators and motors. If the thumb, in- the course of an aircraft in flight, from takeoff to
dex finger, and middle finger of the right hand are landing.
positioned so that they are at right angles to each flight-path deviation The departure of an aircraft
other, the middle finger points in the direction of in flight from the course in the flight plan. Also
an induced voltage, the thumb in the direction of see FLIGHT PATH.
the motion of a conductor, and the index finger in flight-path-deviation meter An instrument that
the direction of the magnetic field. Compare provides a visual indication of the departure of an
FLEMING™S LEFT-HAND RULE. aircraft in flight from the course in the flight plan.
Fletcher-Munson curves A set of curves depicting flight telerobotic servicer A remotely controlled
the uneven frequency response of human hear- robot used to maintain and repair space vehicles
ing. Also called AUDIBILITY CURVES. and satellites. The machine can be controlled by
290 flight telerobotic servicer • floating-point system


a computer program or by a human operator. The floating input An ungrounded input circuit.
most-sophisticated machines can use TELEOP- floating-input measurement See DIFFERENTIAL-
ERATION and/or TELEPRESENCE so that a hu- INPUT MEASUREMENT.
man can perform dangerous work without being floating instrument An instrument whose signal
placed at personal risk. terminals are above ground.
flight test 1. To test airborne electronic equipment floating I/O port An input/output (I/O) terminal
in actual flight. 2. Any test made as in 1. that is not loaded or being driven.
Flinders bar In a magnetic compass, a metal bar floating junction A junction (in a semiconductor
that corrects for the vertical component (inclina- device, for example), that has no net current flow-
tion) of the earth™s magnetic field. The bar must ing through it.
be designed differently in different geographic lo- floating neutral A circuit with a variable common
cations, because the inclination varies from place voltage reference.
to place. Inclination is greatest near the geomag- floating paraphase inverter A dual-transistor
netic poles, and is zero at the geomagnetic equa- adaptation of the paraphase inverter. The second
tor. stage receives its input signal from a tap on the
flint glass A hard, bright, lead glass. Dielectric load resistor of the first stage and provides the
constant, 7 to 9.9. Dielectric strength, 30 to 150 additional phase shift that is required.
kV/mm. Also see GLASS.
flip chip A monolithic semiconductor device (such Output 1
as a diode, transistor, or integrated circuit), in D
which bead-like terminals are provided on one
face of the chip for bonding.
S
flip-chip bonding A scheme for making connec-
tions between a semiconductor chip and a Input
header, in which leads are not run between chip
and header. Instead, bead-like projections are
electrodeposited as terminals around one face of
Common
the chip, which is then registered with the header
terminals and bonded to them.
flip-flop 1. See BISTABLE MULTIVIBRATOR. 2. A
S
two-position relay that locks in alternate posi-
tions upon receiving successive actuating pulses.
D
flip-flop key In a video display, a key that, when Output 2
pressed, allows viewing of one half of the screen
and then the other.
floating paraphase inverter
flip-flop memory A bistable computer memory
that stores bits of data as flip-flop states.
flip-flop relay See BISTABLE RELAY. floating-point calculation An electronic calcula-
float charging The constant charging of a storage tion using a floating point number [i.e., a number
battery, keeping the battery at or near the fully whose value is represented by two sets of digits, a
charged state at all times. fixed-point part (see FIXED-POINT SYSTEM) and
floated battery A storage battery connected in a radix (base number) with an exponent]. Impor-
parallel with a generator, which supplies the tant in the operation of microprocessors, espe-
load; the battery, always completely charged, cially in computer systems.
helps during high-current demands. floating-point number A number expressed in the
floating 1. To float a storage battery; see FLOAT. 2. floating-point system.
An ungrounded device or circuit that is not con- floating-point package Computer-vendor soft-
nected to a source of voltage. 3. Not loaded or ware that enables that computer to perform float-
driven. 4. Not fixed in position. 5. A dedicated ing-point calculations.
ground connection that remains isolated from the floating-point system A system of notation in
common circuit ground. which a number n is represented by two sets of
floating address See RELATIVE ADDRESS. numbers: a fixed-point part (see FIXED-POINT
floating charge See TRICKLE CHARGE. SYSTEM) a, the radix (base number) r, and an ex-
ponent b as follows: n = a — r b. For example, in the
floating control 1. A potentiometer, such as a
floating-point system, 623 can be written 6.23 —
gain control, installed with its shaft insulated
102. Floating-point numbers can be stored eco-
from ground and, accordingly, subject to body-
capacitance effects. 2. A type of automatic control nomically (in terms of memory) and in magni-
in which the rate of final control element move- tudes that might otherwise be beyond the
ment depends on the amount that the controlled capacity of the computer to operate upon with
variable deviates from a prescribed value. relatively consistent accuracy. Compare FIXED-
floating ground See FLOATING, 5. POINT SYSTEM.
291
floating probe • fluorescent materials


floating probe A test electrode (wire or plate) in- fluid analogy The comparison of electric current
serted in a discharge tube at a desired point to flow to the movement of a simple fluid. Also see
sample the potential gradient, but which acquires WATER ANALOGY.
a misleading negative charge, with respect to the fluid capacitor See WATER CAPACITOR.
gas cloud, because electrons (traveling faster fluid computer A digital computer that uses fluid
than the positive ions) tend to accumulate on the logic elements (i.e., one that contains no elec-
probe. tronic circuits or moving parts).

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