USEFUL FORMULAS

Ohm's law

where 1 = current (intensity of current flow) E = voltage (emf ) R = resistance

Resistances in series

Resistances in parallel

Two resistances in parallel

Capacitances in series

Capacitances in parallel

Electric power

where P = power, W 1 hp = 550 ft.lb/s = 746 W

1 J = 1 w/s

Frequency and wavelength

where J' = frequency, Hz h = wavelength, m

Capacitive reactance

where X , = capacitance reactance, S1 f = frequency, Hz C = capacitance, F

Inductive reactance

where X L = inductive reactance, S1 f = frequency, Hz L = inductance, H

Resonant frequency

Impedance: series circuit

Z - d(xL - K c ) ' + R z

where Z = impedance, 0 XL = inductive reactance, fl Xc = capacitance reactance, 52 R = resistance, .R.

Impedace: parallel (tank) circuit

Inductance of a coil

where L = inductance, H N = number of turns of wire on the coil p = permeability of core material A = cross-sectional area of the coil

l = length of the coil, cm

inductances in series, no magnetic coupling

L * = L 1 + L z + L , . . .

Inductances in parallel, no coupling

Figure of merit for a coil

Amplification factor: vacuum tube

hE, CL = AEg (I, constant)

where AE, = change in plate voltage, V AE, = change in control-grid voltage, V

Plate resistance

R, = - hEp (E. constant) MP

where Rp = plate resistance, S1 AEp = change in plate voltage, V Alp = change in plate current, A

Transconductance

G, = 4- (E, constant) AE,

where G, = transconductance, mhos

ABBREVIATIONS

ampere ampere- hour billion electronvolts circular mil coulomb decibel dyne electronvolt erg farad gauss gilbert hen y hertz horsepower joule kilowatthour mho (see siemens) oersted ohm siemens var volt voltampere watt watthour weber

A Ah or A h GeV cmil C dB dyn eV

Oe n S var v V A o r V m A W W h 0 r W . h Wb

Greek Alphabet -- -

Name Capital Lowercase Use in Electronics

Alpha Beta

Gamma Delta Epsilon Zeta

Eta

Theta Iota Kappa Lambda Mu

Nu Xi Omicron Pi

Rho Sigma Tau

Upsilon Phi Chi Psi

Omega

Angles, area, coefficients Angles, flux density,

coefficients Conductivity Variation, density

Impedance, coefficients, coordinates

Hysteresis coefficient, efficiency

Temperature, phase angle Current Dielectric constant Wavelength Micro, amplification factor,

permeability Reluctivity

Ratio of circumference to diameter t3.1416)

Resistivity, density Sign of summation Time constant, time phase

displacement

Magnetic flux, angles

Dielectric flux, phase difference

Capital, ohms; lowercase angular velocity

Copper Wire Single Strand, American Wire Gage

QUALIFYING SYMBOLS

Resistance, Diameter Cross section. fl/1000 ft Weight,

Gage mils cir mils (25") lb/1000 ft

ELECTRICAL AND

ELECTRONIC SYMBOLS

The symbols shown here are those that are likely to be encountered by the aviation maintenance technician. Only the p imiry symbols are provided in this section. For the additional symbols representing variations of the primary symbols, the technician should consult the docu- ment "Graphic Symbols for Electrical and Electronics Diagrams" published by the Institute of Electrical and Electronic Engineers (IEEE), IEEE Std 315-1975, or ANSI Y32.2-1975 furnished by the American National Standards Institute. Symbols shown usually comply with International Electronicaf Commission (IEC) Publication 117.

Qualifying symbols are applied to standard symbols to / provide an indication of the special characteristics of the I symbols as they are employed in specific circuits.

ADJUSTABILITY OR VARIABILITY

CONTINUOUSLY PRESET, LINEAR NONLINEAR; ADJUSTABLE OR GENERAL

VARIABLE CONDITION

SPECIAL PROPERTY INDICATORS

to X 7

TEMPERATURE MAGNETIC FIELD (GREEK LETTER TAU[ DEPENDENCE DEPENDENCE STORAGE

SATURABLE PROPERTIES

w DELAY

RADIATION INDICATORS

RADIO WAVES RADIATION. OR VISIBLE LIGHT IONIZING

Type of radiation Alpha particle Neutron 1 a 'I

Beta particle Pion P 7T

Gamma ray K-meson Y K

Deutron 6

Proton P

PHYSICAL-STATE RECOGNITION SYMBOLS

Muon 1 P

X-ray X

w // &?--,,I GAS, Al R, OR LIQUID SOLID ELECT RE^ PNEUMATIC MATERIA!

TEST-POINT RECOGNITION SYMBOL

TERMINAL

CAPACITOR DIRECTION OF FLOW OF POWER, SIGNAL, OR INFORMATION - - -

OR OR OR - - -

ONE WAY EITHER WAY, BUT NOT BOTH WAYS, SIMULTANEOUSLY SIMULTANEOUSLY

L--2

GENERAL SHIELDED FEEDTHROUGH

POLARIZED -

7+F- VARIABLE VARIABLE T-T WITH MECHANICAL LINKAGE

KIND OF CURRENT (GENERAL)

OR TL ---+------ ALTERNATING

DIRECT CURRENT CURRENT ANTENNA

yo" GENERAL 1 DIPOLE lr ! CONNECTION SYMBOLS

L TWO-PHASE, TWO-PHASE, THREE-WIRE, THREE-WIRE, UNGROUNDED GROUNDED

LOOPS _L

TWO-PHASE, FIVE-WI RE, GROUNDED

TWO-PHASE. FOUR-WI RE

ONE-CELL MULTICELL

THREE-PHASE, THREE-WIRE, THREE PHASE, THREE-WIRE DELTA OR MESH DELTA, GROUNDED ALTERNATING-CURRENT SOURCE

AC GENERATOR @ OR ALTERNATOR

THREE-PHASE, FOUR-WIRE, THREE-PHASE, FOUR-WI RE, DELTA, UNGROUNDED DELTA, GROUNDED PERMANENT MAGNET

THREE-PHASE, WYE OR STAR, THREE-PHASE, WYE OR STAR, UNGROUNDED GROUNDED PICKUP HEAD

---4-> GENERAL STEREO

FUNDAMENTAL ITEMS

RESISTOR PIEZOELECTRIC CRYSTAL UNIT

GENERAL TAPPED RESISTOR

THERMOCOUPLES

BUILDUP EXAMPLE BU1 LDUP EXAMPLE I (ADJUSTABLE CONTACT) (VARIABLE RESISTOR)

--vA- THERMAL RESISTOR PHOTOCONDUCTlVE

(THERMISTOR) TRANSDUCER

THERMOCOUPLE WlTH INTEGRAL INSULATED

HEATER

TEMPERATURE-MEASURING THERMOCOUPLE WlTH

INTEGRAL HEATER

ACTUATING THERMAL CIRCULAR RECTANGULAR RIDGED

DEVICE CUTOUT CONTACTS, SWITCHES, CONTACTORS AND RELAYS

IGNITOR PLUG

SWITCHING FUNCTION

CONDUCT1 NG, NONCONDUCTING, CLOSED CONTACT (BREAK) OPEN CONTACT (MAKE) TRANSMISSION PATH

SWITCH CONDUCTOR, CABLE, WIRING

GUIDED PATH, GENERAL BUS BAR

OR OR

d o 0 d o SINGLE-THROW GENERAL DOUBLE-THROW GENERAL OR + 61

I

THREE-CONDUCTOR PATH SIX-CONDUCTOR PATH

BUILDUP EXAMPLE: TWO-PO LE

DOUBLE-THROW SWITCH 0 d o BUILDUP EXAMPLE:

THREE-POLE DOUBLE-THROW

2- KNIFE WITH TERMINALS AND AUX. CONTACTS

OR

/ o 1 0 0

KNIFE SWITCH,GENERAL Cl RCUIT CLOSING (MAKE)

CROSSING NOT CONNECTED

JUNCTION CONDUCTORS CONNECTED

& TWISTED PAIR

MULTIWAY TRANSFER SWITCH L QUAD

- FIVE-CONDUCTOR CABLE SHIELDED FIVE-CONDUCTOR

CAB LE TWO-POSITION THREE-POSITION FOUR-POSITION

SWITCH (90" STEP) SWITCH (120° STEP) SWITCH (45" STEP)

PUSHBUTTON

SHIELDED TWO-CONDUCTOR CAB t E WlTH SHIELD GROUNDED

COAXIAL CIRCUIT CLOSING Cl RCUlT OPENING 0 0

(MAKE) (BREAK) TWO CIRCUIT

LOCKING SWITCH

Cl RCUIT CLOSING (MAKE) Cl RCUIT OPENING (BREAK)

+ -r OR < 0 + OFF

0 - TRANSFER SWITCH, TRANSFER, MAKE-BEFORE-

TWO-POSITION THREE-POSITION BREAK

GROUPING OF LEADS

CHASSIS OR FRAME CONNECTION

NONLOCKING SWITCH, MOMENTARY OR SPRING RETURN

o---- t 0"-

Cl RCUiT CLOSING (MAKE) Cl RCUIT OPENING (BREAK)

- - - r - - TWO-CIRCUIT

TRANSFER MAKE-BEFORE-BREAK

SELECTOR OR MULTlPOSlTlON SWITCH

0 0 BREAK-BEFORE-MAKE. MAKE-BEFORE-BREAK, NONSHORTING DURING SHORTING (BRIDGING)

CONTACT TRANSFER DURING CONTACT TRANSFER

d b 0 OR

p - 4 o o o O ~ n q TWELVE-POINT SELECTOR SWITCH

SEGMENTAL CONTACT WITH FIXED SEGMENT

WAFER. TYPICAL THREE-POLE

-+ - THREE-CIRCUIT WITH TWO NONSHORTING AND ONE 4 SHORTING MOVABLE CONTACTS

LIMIT SWITCH

TRACK-TYPE, TRACK-TYPE, CI RCUlT CLOSING CONTACT CIRCUIT OPENING CONTACT

v'-- Dl RECTLY-ACTUATED,

SPRING RETURN

NORMALLY OPEN, HELD CLOSED

NORMALLY OPEN

e NORMALLY CLOSED, NORMALLY CLOSED HELD OPEN

FLOW-ACTUATED SWITCH

T CLOSES ON INCREASE IN FLOW OPENS ON INCREASE IN FLOW

LIQUID-LEVEL-ACTUATED SWITCH

6 0 CLOSES ON RISING LEVEL OPENS ON RISING LEVEL

PRESSURE OR VACUUM-ACTUATED SWITCH

CLOSES ON RISING PRESSURE OPENS ON RISING PRESSURE

TEMPERATURE-ACTU ATED SWITCH (THERMOSTAT)

CLOSES ON RlSlNG TEMPERATURE

OPENS ON RISING TRANSFERS ON RISING TEMPERATURE TEMPERATURE

FLASHER

SELF- INTERRUPTING SWITCH

CONTACTOR

I I I ELECTRICALLY-OPERATED MANUALLY-OPERATED, ONE-POLE CONTACTOR WITH

THREE-POLE CONTACTOR SERIES BLOWOUT COIL

RELAYS

GENERAL SYMBOLS FOR RELAY COILS

RELAY WITH TRANSFER CONTACTS

LElTER COMBINATlONS THAT MAY BE USED WITH RELAY SYMBOLS

AC Alternating current or ringing relay D Differential DB Double-biased EP Electrically polarized FO Fast-operate FR Fast release L Latching MG Marginal ML Magnetic-latching NB No bias NR Nonreactive P Magnetically polarized E E I SA Slow-operate and slow-release SO Slow-operate n SR Slow-release n SW Sandwich-wound to improve balance to longitudi-

nal currents

TERMINALS AND GUNNtC; I UKS L U A A I W L L U l U l Y t L l VK

TERMINALS

0

Cl RCUiT TERMINAL

TERMINAL STRIP WlTH FOUR TERMINALS

COAXIAL WITH OUTSIDE COAXIAL WITH OUTSIDE CONDUCTOR CARRIED CONDUCTOR TERMINATED

THROUGH ON CHASSIS

TRANSFORMERS, INDUC- TORS AND WINDINGS

TERMINALS FOR ELECTRON TUBES

SMALL- RIG1D

FLEXIBLE 'IN LARGE- 0 PIN

CORE SYMBOLS

No symbol is used for an air core BASE PIN TERMINALS ENVELOPE TERMINALS

MAGNETIC CORE OF INDUCTOR OR COREOF

TRANSFORMER MAGNET DEVICE WITH BASE- DEVICE WITH ORIENTATION KEY REFERENCE POINT

INDUCTOR CABLE TERMINATION - OR m m

GENERAL MAGNETIC CORE

T TAPPED

SYMBOLS INDUCTOR INDUCTOR

L

CABLE AT LEFT OF SYMBOL

ADJUSTABLE CONTINUOUSLY COI L-OPERATED INDUCTOR ADJUSTABLE INDICATOR CONNECTORS

TRANSDUCTOR FEMALE < CONTACT MALE > CONTACT

- CONTROL WINDING-DC =

YL_ POWER WINDING-AC

SATURABLE-CORE INDUCTOR OR REACTOR RECEPTACLE PLUG CONNECTORS ENGAGED

TRANSFORMER (Type of contacts in connectors are indicated as male or female. )

GENERAL WINDING SYMBOLS

MALE PLUG, FEMALE RECEPTACLE, ENGAGED

IF IT IS DESIRED TO

0" I %

TWO-CONDUCTOR JACK TWO-CONDUCTOR PLUG

DlSTlNGUlSH A MAGNETIC SHIELDED TRANSFORMER CORE TRANSFORMER WITH MAGNETIC CORE

POWER SUPPLY CONNECTORS

ONE WINDING WlTH ADJUSTABLE INDUCTANCE

NONPOLARIZED MALE CONNECTOR

NONPOLARIZED FEMALE CONNECTOR

SEPARATELY ADJUSTABLE ADJUSTABLE MUTUAL l NDUCTANCES INDUCTOR, CONSTANT

CURRENT TRANSFORMER

I I POLARIZED

FEMALE CONNECTOR

POLARIZED THREE-CONDUCTOR CONNECTOR, MALE AUTOTRANSFORMER, ONE-PHASE

CATHODE-RAY TUBE

CRT WlTH ELECTRIC FIELD DEFLECTION

THREE-PHASE BANK TRANSFORMERS WI

OF ONE-PHASE, TWO-WINDING TH WYE-DELTA CONNECTIONS SEMICONDUCTOR DEVICES

ELECTRON TUBES AND RELATED DEVICES TRANSISTORS AND DIODES

ELEMENT SYMBOLS ELECTRON TUBE

I SEMICONDUCTOR

+ OR f OR 7-T SEMICONDUCTOR

REGION WITH ONE REGION WITH TWO OHMIC CONNECTION OHMIC CONNECTIONS

EMITTING ELECTRODE

A DIRECTLY HEATED

CATHODE (EMITTER) OR HEATER

n lNDl RECTLY HEATED

CATHODE

P REGION ON N REGION N REGION ON P REGION + PHOTOCATHODE

4

COLD CATHODE

(Arrow points opposite electron flow) CONTROLLING ELECTRODE

P EMITTER ON PLURALITY OF P N EMITTER Oh N REGION EMITTERS ON N REGION P REGION

----

GRID

4 DEFLECTING ELECTRODES

(USED IN PA1 RS)

IGNITOR (FOR POOL TUBES)

EXCITOR (CONTACTOR TYPE)

COLLECTOR ON REGION O f DISSIMILAR CONDUCTIVITY

TYPE PLURALITY OF COLLECTORS COLLECTING ELECTRODE

TWO-TERMINAL DEVICES

ANODE OR TARGET OR FLUORESCENT COLLECTOR PLATE X-RAY ANODE TARGET

ANODE TUBE SYMBOLS STYLE 1 STYLE 2

DIODE RECTIFIER CAPACITIVE DIODE (VARACTOR)

PHOTOSENSITIVE DlODE

PHOTOEMISSIVE (LIGHT EMITTING) DlODE (LED)

TRIODE WITH DIRECTLY EQUIPOTENTIAL-PENTODE HEATED CATHODE INDIRECTLY HEATED CATHODE

@ PNP

BID1 RECTIONAL PHOTODIODE

EQUIPOTENTIAL-CATHODE COLD-CATHODE, GAS-FILLED TWIN TRIODE RECTIFIER

X-RAY TUBE STYLE 1 STYLE 2 (ZENER) UNIDIRECTIONAL DIODE: VOLTAGE REGULATOR

WlTH FILAMENTARY CATHODE AND FOCUSING GRID (CUP)

STYLE 1 8 8 STYLE 2

BIDIRECTIONAL DIODE

CATHODE (K) ANODE (A) n - - GENERAL NETWORK PROTECTOR w

NPN TYPE w

PNP TYPE UNIDiRECTIONAL NEGATIVE-RESISTANCE BREAKDOWN DIODE;

TRIGGER DlAC CIRCUIT BREAKER WlTH THERMAL OVERLOAD DEVICE

NPN TYPE PNP TYPE

BID l RECTIONAL NEGATIVE-RESISTANCE BREAKDOWN DIODE; TRIGGER DlAC

CIRCUIT BREAKER WlTH MAGNETIC OVERLOAD DEVICE

ACOUSTIC DEVICES

AUDIBLE SIGNALING DEVICE

w PHOTOTRANSISTOR

CURRENT REGULATOR

BELLS, ELECTRICAL-SIGNALLING; TELEPHONE RINGER

THREE-OR-MORE-TERMINAL DEVtCES SINGLE-STROKE BELL BUZZER

PNP TRANSISTOR

B

E@NPN TRANSISTOR

DRAIN (D) GATE (G)

SOURCE (S)

FIELD EFFECT TRANSISTOR (FET) WlTH N-CHANNEL JUNCTION GATE

G

FET WlTH INSULATED GATE

HN -HORN

HW-HOWLER

EM -ELECTROMAGNETIC WlTH MOVING COIL

EMN-E LECTROMAGNETIC WlTH MOVING COIL AND NEUTRALIZING WINDING

MG -MAGNETIC ARMATURE PM -PERMANENT MAGNET

MICROPHONE, TELEPHONE TRANSMllTER

G THYRISTOR, THYRISTOR, GATE TURN-

STYLE 1 STYLE 2 OFF TYPE

MICROPHONE, GENERAL

HANDSET THYRISTOR, BIDIRECTIONAL B

TRIODE-TYPE; TRlAC PHOTOTRANSISTOR WlTH PUSH-

GENERAL TO-TALK SWITCH CIRCUIT PROTECTORS

FUSES TELEPHONE RECEIVER

e OR --(I_IE- OR -L-- GENERAL FUSE SYMBOLS - s r *+ , L

FUSE WITH SUPPLY I I

HEADSET, DOUBLE HEADSET, SINGLE

SIDE INDICATED BY FUSE WITH ISOLATING FUSE A WIDE LINE ALARM CONTACT SWITCH LAMPS AND VISUAL-

SIGNALING DEVICES CURRENT LIMITER

LAMP LIGHTNING ARRESTOR -- --+I+ -- ++ GENERAL CARBON BLOCK HORN GAP PROTECTIVE GAP LAMP, GENERAL; LIGHT SOURCE

AMBER OPALES- CENT PURPLE RED WHITE YELLOW INFRA- RED SODIUM VAPOR NEON ULTRA- VIOLET XENON LIGHT- EMIT- TING DIODE

PH PI RD REC RF S To THC TLM TT

Phase meter Position indicator Recording demand meter Recording Reactive-factor meter Synchroscope Temperature meter Thermal convertor Telemeter Total-time meter Elapsed-time meter Voltmeter Volt-ammeter Varmeter Varhour meter Volume indicator Audio-level meter Standard volume indicator Audio-level meter Wattmeter Watthour meter

B C G 0 ARC

BLUE CLEAR GREEN ORANGE ARC

ELECTROLUMINESCENT

FLUORESCENT MERCURY VAPOR v

VA VAR VARH VI

INCANDESCENT XE LED

u FOUR-TERMINAL TWO-TERMINAL

FLUORESCENT LAMPS GALVANOMETER

ROTATING MACHINERY

ROTATING MACHINE 1 GLOW LAMP, AC TYPE GLOW LAMP, DC TYPE

0 BASIC

@ O R @ GENERATOR, GENERAL

0 GENERATOR, DC

- 1/

COMMUNICATION-SWITCHBOARD LAMP

1 READOUT DEVICES

GENERATOR, AC

GENERATOR, SYNCHRONOUS

@ O R @

MOTOR, GENERAL

' METER INSTRUMENT

0 GENERAL

MOTO R, DC

MOTOR, AC

MOTO R, SYNCHRONOUS

A AH C CMA CMC CMV CRO DB DBM DM DTR F GD I INT uA or UA MA NM OHM OP ' OSCG

i PF

Ammeter Ampere-hour meter Coulombmeter Contact-making (or breaking) ammeter Contact-making (or breaking) clock Contact-making (or breaking) voltmeter Cathode-ray oscilloscope DB (Decibel) meter DBM (Decibels referred to 1 mW) meter Demand meter Demand-totalizing relay Frequency meter Ground detector Indicating meter Integrating meter Microammeter Milliammeter Noise meter Ohmmeter Oil pressure Oscillograph, string Power-factor meter

FIELD, GENERATOR OR MOTOR

A - - COMPENSATING SERIES SHUNT OR

OR COMMUTATING SEPARATELY EXCITED

WINDING CONNECTION SYMBOLS

ONE-PHASE TWO-PHASE THREE-PHASE THREE-PHASE WYE WYE

UNGROUNDED GROUNDED

TH REE-PHASE, SI X-PHASE, SIX-PHASE, DELTA DIAMETR ICAL DOUBLE DELTA

UIHtCI I-CURRENT MACHINES

- - SEPARATELY EXCITED DC GENERATOR OR

MOTOR WlTH COMMUTATlNG FIELD WINDING

SERIES MOTOR OR TWO-WIRE DC GENERATOR WlTH COMMUTATING FlELD WINDING OR BOTH

SYMBOLS USED IN LOGIC CIRCUITS AND DIAGRAMS

(Not included in ANSI Y32.2)

AMPLIFIERS

GENERAL SYMBOLS MAGNETIC AMPLIFIER

LOGIC GATES

DC COMPOUND MOTOR OR STAB1 LlZED SHUNT MOTOR WlTH COMMUTATING FlELD WINDING

DC, PERMANENT-MAGNET FlELD GENERATOR OR MOTOR

. . , .

DYNAMOTOR

ALTERNATING-CURRENT MACHINES

SQUIRREL-CAGE INDUCTION MOTOR OR GENERATOR. SYNCHRONOUS MOTOR OR GENE RATOR, SPLIT-PHASE INDUCTION

MOTOR OR GENERATOR, ROTARY-PHASE CONVERTOR, OR REPULSION MOTOR

WOUND-ROTOR INDUCTION MOTOR, SYNCHRONOUS INDUCTION MOTOR, INDUCTION GENERATOR, OR INDUCTION

FREQUENCY CONVERTOR

AC SERIES MOTOR

I * - AC SERIES MOTOR WITH COMMUTATING OR COMPENSATING FlELD WINDING OR BOTH

AND GATE WITH THREE INPUTS NAND (NOT AND) GATE

3l+ OR GATE s

NOR (NOT OR) GATE

0-- - - SYNCHRONOUS MOTOR OR GENERATOR

WlTH DC FIELD EXCITATION

accelerate: To change velocity, that is, increase or decrease speed. accelerometer: A device for sensing or measuring accelera- tion and converting it to an electric signal. acceptor: An impurity atom in a semiconductor material which will receive or accept electrons. Germanium with an ac- ceptor impurity is called p-type germanium because it has a pos- itive nature. actuator: A hydraulic, electric, or pneumatic device used to operate a mechanism by remote control on a-plane or missile. alignment, electric: The tuning of electronic components in a particular circuit so that ail portions of the circuit will respond to the correct frequency. alternating current (ac as adjective): An electric current which periodically changes in direction and constantly changes in magnitude. alternation: The part of an ac cycle during which current is flowing in one direction; one-half a cycle. alternator: An electric generator designed to produce alter- nating current. ammeter: An instrument used to measure current flow. ampere (A): The basic unit of current flow. One ampere is the amount of current which flows when an emf of 1 V is applied to a circuit with a resistance of 1 R. One coulomb per second. ampere-hour (Ah): The quantity of electricity which has passed through a circuit when a current of 1 A has flowed for 1 h. Current (in amperes) x time (in hours) = ampere-hours. One Ah is equal to 3600 C. ampere-turn: The magnetizing force produced by a current of 1 A flowing through one turn of a coil. Ampere-turns = am- peres x number of turns of wire in the coil. amplication: The increase of power, current, or voltage in an electronic circuit. amplication factor: The ratio of a small change in plate volt- age to a small change in grid voltage when the plate circuit is operating through a load. It is denoted by the Greek letter mu (p) . Amplification factor for a transistor is the ratio of change in emitter current to a change in base current. amplifier: An electronic circuit designed to produce amplifica- tion. amplitude modulation (AM): Modulation of a carrier wave in which the modulating signal changes the amplitude of the car- rier in proportion to the strength of the modulating signal. angular velocity: Time rate of change of an angle rotated around an axis in degrees per second or degrees per minute. anode: Positive electrode of a battery; the electrode of an elec- tron tube, diode, or electroplating cell to which a positive volt- age is applied.

antenna: A device designed to radiate or intercept electro- magnetic waves. armature: In a dc generator or motor, the rotating member. In an ac generator the armature is stationary and is acted upon by the rotating field produced by the rotor. The moving element acted upon by the magnetic field in a relay is also called the ar- mature. armature reaction: The interaction of the armature field upon the main field of a generator or motor, resulting in distortion of the main field. atom: The smallest possible particle of an element. attenuation: A reduction in the strength of a signal, the flow of current, flux, or other energy in an electronic system. audio frequency (AF as adjective): A frequency in the audi- ble range, generally considered to be from about 35 to 20 000 Hz. automatic direction finder (ADF): A radio receiver utilizing a directional loop antenna which enables the receiver to indicate the direction from which a radio signal is being received; also called radio compass. automatic flight-control system (AFCS): A flight-control system incorporating an automatic pilot with additional systems such as a VOR coupler, an ILS approach coupler, and an inter- nal navigation system which is fully automatic, so the aircraft can be flown in a completely automatic mode. automatic frequency control (AFC): A circuit arrangement which maintains the frequency of the system within specified limits. automatic pilot: A system installed in an airplane or missile which senses deviations in the flight path and moves the control surfaces to maintain the selected flight path. automatic volume control (AVC): A circuit arrangement in which the dc component of the detector output in a radio re- ceiver controls the bias of the rf tubes, thus regulating their out- put to maintain a reasonably constant volume. Autosyn: A trade name of the Bendix Corporation used to designate certain types of synchro devices. azimuth: Angular distance measured on a horizontal circle in a clockwise direction from either north or south. ballast: A circuit element designed to stabilize current flow. band: A range of frequencies. bandpass filter: A filter circuit designed to pass frequencies within a specific band and attenuate frequencies outside the band. bandwidth: The difference between the maximum and mini- mum frequencies in a band. base: The terminal of a transistor to which the controlling cur- rent is applied.

battery: A group of voltaic cells connected together to pro- duce a desired voltage and current capacity. Typical batteries utilize primary cells, secondary cells, and photovoltaic cells. beam power tube: An electron tube which utilizes directed electron beams to add to its power-handling capability. beat frequency oscillator (BFO): An oscillator designed to produce a signal frequency which is mixed with another fre- quency in order to develop an intermediate frequency or an audio frequency. bel: A unit used to express the ratio of two values of power. The number of bels is the logarithm to the base 10 of the power ratio. bias: A voltage applied to the control grid of an electron tube or the control element of a transistor to establish the correct operating point. binary system: A numbering system using only two symbols 0 and I and having 2 as a base. In the decimal system, 10 symbols are used and the base is 10. bit: One unit of a binary number. bleeder resistance: A permanently connected resistor con- nected across the output of a power supply and designed to "bleed-off' a small portion of the current. bonding: The connecting together of metal structures with electric conductors, thus establishing a uniform electric potential among all the parts bonded together. breakdown voltage: Breadkdown voltage in a capacitor is that voltage at which the dielectric is ruptured, or the voltage level in a gas tube at which the gas becomes ionized and starts to conduct. brush: A device designed to provide an electrical contact be- tween a stationary conductor and a rotating element. buffer amplifier: An amplifier in a transmitter circuit designed to isolate the oscillator section from the power section, thus pre- venting a frequency shift. bus bar: A power distribution point to which a number of cir- cuits may be connected. It oftens consists of a solid metal strip in which a number of terminals are installed. cable: A group of insulated electric conductors, usually cov- ered with rubber or plastic to form a flexible transmission line. capacitance: The property enabling two adjacent conductors separated by an insulating medium to store an electric charge. The unit of capacitance is the farad. capacitive reactance: The reactive effect of capacitance in an ac circuit. The formula is X, = $7~fC, where X, is capacitive reactance in ohms, f is frequency in hertz, and C is the capaci- tance in farads. capacitor: A device consisting of conducting plates separated by a dielectric and used to introduce capacitance into a circuit. carrier wave: A radio-frequency electromagnetic wave used to convey intelligence impressed upon it by modulation. cathode: (1) The negative electrode of a battery; (2) the ele- ment in an electron tube which emits electrons into the intere- lectrode space; (3) the negative terminal of a diode or electroplating cell. cathode-ray tube (CRT): A special type of electron tube in which a stream of electrons from an electron gun impinges upon a fluorescent screen, thus producing a bright spot on the screen. The electron beam is deflected electrically or magnetically to produce patterns on the screen. - characteristic curve: A graph which shows the performance of an electron tube or a transistor under various operating con- ditions. charge: A quantity of electricity. A charge is negative when it consists of a number of electrons greater than the number nor- mally held by the charged material in a neutral condition. The charge is positive when there is a deficiency of electrons.

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choke coil: An inductance coil designed to provide a high reactance to certain frequencies and generally used to block or reduce currents at these frequencies. circuit: Conductors connected together to provide one or more complete electrical paths. circuit breaker: A device which automatically opens a circuit if the current flow increases beyond an established limit. circuit protection: The provision of devices in an electric cir- cuit to prevent excessive current flow. These devices may be fuses, circuit breakers, current limiters, or sensing relays. circular mil (crnil): The cross-sectional area of a circle having a diameter of 1 mil (0.001 in). The circular mil is used to indicate the size of electric wire. clutch: A mechanical device used to connect or disconnect a motor or other driving unit from the driven device. coaxial cables: A pair of concentric conductors. The inner conductor is supported by insulation which holds it in the center of the outer conductor. A coaxial cable is normally used to con- duct HF currents. coil: One or more turns of a conductor designed for use in a circuit to produce inductance or an electromagnetic field. collector: The section of a transistor corresponding to the plate in an electron tube. collector ring: A rotating electrical contact used with a brush to transfer electric current from a rotating unit to a stationary unit or vice versa. color code: A system of colors used to indicate component values, or identify wires and terminals. commutator: A rotating contact device in the armature of a dc generator or motor, which in effect changes the ac current flow- ing in the armature windings to a dc current in the external cir- cuit. compass: A device used to determine direction on the earth's surface. A magnetic compass utilizes the earth's magnetic field to establish direction. compound winding: A combination of series and parallel or shunt windings to provide the magnetic field for a generator or motor. conductance: The reciprocal of resistance. conductor: A material through which an electric current can pass easily. conduit: A metallic tubular sheath through which insulated conductors are run. The conduit provides mechanical protection and electric or magnetic shielding for the conductors. continuity tester: A device designed to test the electrical conti- nuity of a conductor or circuit. A battery and light, or other indi- cating unit, connected in series, or an ohm-meter may serve as continuity testers. continuous wave (CW): An RF carrier wave whose successive oscillations are identical in magnitude and frequency. control circuit: Any one of a variety of circuits designed to ex- ercise control of an operating device, to perform counting, tim- ing, switching, and other operations. control grid: The grid nearest the cathode in an electron tube. The charge on the control grid governs the flow of electrons from cathode to plate. corona loss: Power loss due to the ionization of gas adjacent to a high-potential conductor. cosine: The ratio of the side adjacent to an acute angle of a right triangle to the hypotenuse. coulomb (C): The international coulomb is a unit of electric charge consisting of approximately 6.28 x 10IH electrons. The absolute coulomb is slightly greater than the international cou- lomb; that is, I absolute coulomb = 1.000165 international coulomb.

counter electromotive force (cemf): A voltage developed in the armature of a motor which opposes the applied emf. The same principle applied to any inductance through which an al- ternating current is flowing. counterpoise: One or more conductors used under certain types of antennas to take the place of the usual ground circuit. coupling: Energy transfer between elements or circuits of an electronic system. cross modulation: The modulation of a desired signal by an unwanted signal resulting in two signals in the output. crystal: A solid body with symmetrically arranged plane sur- faces. In electronic systems, crystals are used as rectifiers, semi- conductors, transistors, and frequency controllers and to produce oscillatory voltages. crystal diode: A diode constructed from a crystal semiconduc- tor material such as silicon or germanium. current: The movement of electricity through a conductor, i.e., the flow of electrons through a conductor. current limiter: A device installed in a circuit to prevent cur- rent from increasing above a specified limit. cutoff: The point at which an operation stops because a cutoff condition has been reached. In electron tubes, the point at which grid bias voltage stops the flow of electrons from cathode to plate. cycle: A complete sequence of events in a recurrent selies of similar periods. damping: The decay in amplitude or strength of an oscillatory current when energy is not introduced to replace that lost through circuit resistance. d'Arsonva1 meter movement: A meter movement consisting of a movable coil suspended on pivots between the poles of a permanent magnet. decades: A series of quantities in multiples of 10, for example, 10, 100, 1000, 10 000. decibel (db): One-tenth of a bel. decoupling: The process of eliminating electrical or magnetic coupling between units in an electronic system. deflection: The movement of an electron beam up and down or sideways in response to an electric or magnetic field in a cath- ode-ray tube. degeneration: Feedback of a portion of the output of a circuit to the input in such a direction that it reduces the magnitude of the input; also called negative feedback. Degeneration reduces distortion, increases stability, and improves frequency response. delta connection: A method of connecting three components to form a three-sided circuit, usually drawn as a triangle, hence the term delta. Delta (A) is the Greek letter corresponding to the English D. demodulation: The recove y of the AF signal from an RF car- rier wave. Also called detection.

dectector: That portion of an electronic circuit which demod- ulates or detects the signal. deviation, compass: The error in a magnetic compass due to construction, installation, and nearby magnetic materials. diac: A negative-resistance breakdown diode, constructed in both unidirectional and bidirectional forms. dielectric: An insulating material used to separate the plates of a capacitor. dielectric constant: A measure of the effectiveness of a di- electric for holding a charge in a capacitor. Air is given a dielec- tric constant of 1; mica has a dielectric constant of 5.5; hence, a capacitor having mica as a dielectric will have a capacitance 5.5 times as great as the same capacitor with a dielectric of air. differentiating circuit: A circuit which produces an output voltage proportional to the rate of change of the input.

diode: A semiconductor device or an electron tube with only a cathode and anode, usually used as rectifiers and detectors. dipole antenna: An antenna consisting of two equal lengths of wire or other conductor extending in opposite directions from the input point. Each section of the dipole is approximately one- quarter wavelength. direct current (dc a s adjective): An electric current which flows continuously in one direction. directional gyro: A direction-indicating instrument which uti- lizes a gyroscope to hold the moving element in a fixed position relative to a directional reference. discriminator: A circuit whose output polarity and magnitude are determined by the variations of the input phase or fre- quency. distance-measuring equipment (DME): An electronic sys- tem used with radio navigation equipment to provide an indica- tion of the distance to a specific point. distortion: Undesirable change in the waveform of the output of a circuit compared with the input. donor: An impurity used in a semiconductor to provide free electrons as current carriers. A semiconductor with a donor im- purity is of the n type. doppler effect: The effect noted as one moves toward or away from a source of a sound-wave or electromagnetic-wave propa- gation. Moving toward the source results in receiving a higher- frequency sound or signal than the source is emitting, and mov- ing away from the source results in receiving a lower-frequency sound or signal. duplexer: A circuit which makes it possible to use the same an- tenna for both transmitting and receiving without allowing ex- cessive power to flow to the receiver. dynamotor: An electric rotating machine with a double arma- ture, usually designed to produce a high dc voltage for plate cir- cuits in radio transmitters and receivers. One end of the armature serves a low-voltage dc motor, and the other end is wound for a high-voltage dc generator. dynatron effect: The area of operation in a tetrode electron tube where plate current decreases as plate voltage increases. This effect is caused by secondary emission from the plate and by the attraction of the seconda y electrons to the screen grid. dynode: The elements in a multiplier tube which emit second- ary electrons. eddy currents: Currents induced in the cores of coils, trans- formers, and armatures by the changing magnetic fields asso- ciated with their operation. These currents cause great losses of energy. For this reason such cores are composed of insulated laminations which limit the currents paths. Edison effect: The discovery of Thomas A. Edison in 1883 that a heated filament placed in an evacuated tube with another electrode will emit electrons. effective value: A term used to indicate the actual working value of an alternating current based upon its heating effect. Also called the root-mean-square (rms) value and is equal to 1/a times the maximum value in a sinusoidal current. electret: A dielectric body in which a permanent state of elec- tric polarization has been set up. Also, the material of which an electret is composed. electricity: In general terms electricity may be said to consist of positive or negative charges at rest or in motion. electrode: A terminal element in an electric device or circuit. Some typical electrodes include the plates in a storage battery, the elements in an electron tube, and the carbon rods in an arc light. electrolysis: The process of decomposing a chemical com- pound by means of an electric current. electrolyte: Any solution which conducts an electric current.

electromagnet: A magnet formed when an iron core is placed in a current-carrying coil. electromagnetic induction: The transfer of electric energy from one conductor to another by means of a moving electro- magnetic field. A voltage is produced in a conductor as the mag- netic lines of force cut or link with the conductor. The value of the voltage produced by electromagnetic induction is propor- tional to the number of lines of force cut per second. When 100 000 000 lines of force are cut per second, an emf of 1 V will be induced. electromagnetism: The magnetism produced by the flow of electric current. electromotive force (emf): The force which causes current to move through a conductor. The unit of measurement for emf is the volt; hence, emf is often called voltage. electron: A negatively charged nonnuclear particle which orbits around the nucleus of an atom. Generally speaking, the electron may be considered the carrier of electric current through a conductor. An electron at rest has a mass of 9.107 x

g and a charge of 1.6 x 10-l9 C. electron gun: The combination of an electron-emitting cath- ode together with accelerating anodes and beam-forming elec- trodes to produce the electron beam in a CRT. electron tube: A device consisting of an evacuated or gasfilled envelope containing electrodes for the purpose of controlling electron flow. The electrodes are usually a cathode (electron emitter), a plate (anode), and one or more grids. electrostatic field: The field of electric force existing in the area around and between any two oppositely charged bodies. elements: Any substance which cannot be changed to an- other substance except by nuclear disintegration. There are more than 100 known elements. emission, electronic: The freeing of electrons from the sur- face of a material, usually produced by heat. emitter: The electrode in an electron tube which emits elec- trons, that is, the cathode; also the electrode in a transistor from which current carriers enter the interelectrode region. equalizer circuit: A circuit in a multiple-generator voltage-reg- ulator system which tends to equalize the current output of the generators by controlling the field currents of the several genera- tors. excitation: The application of electric current to the field windings of a generator to produce a magnetic field; also the input signal to an electron tube. fading: A decrease in strength of a received radio signal. farad: The unit of capacitance; the capacitance of a capacitor which will store 1 C of electricity when an emf of 1 V is applied. feedback: A portion of the output signal of a circuit returned to the input. Positive feedback occurs when the feedback signal is in phase with the input signal. Negative feedback occurs when the feedback signal is 180" out of phase with the input signal. ferromagnetic materials: Magnetic materials composed largely of iron. fidelity: The degree of similarity between the input and output waveforms of an electronic circuit. field: A space in which magnetic or electric lines of force exist. field coil: A winding or coil used to produce a magnetic field. field frame: The main structure of a generator or motor within which are mounted the field poles and windings. filament: A resistive element in an electron tube which sup- plies the heat necessary for themionic emission of electrons; also the heated element in an electric light bulb. filter: A circuit arranged to pass certain frequencies while at- tenuating all others. A high-pass filter passes high frequencies and attenuates low frequencies; a low-pass filter passes low fre- quencies and attenuates high frequencies.

flux: klectrostatic or magnetic lines of force. flux gate: An electromagnetic sensing device designed to de- termine the direction of the earth's magnetic field and thus pro- duce magnetic-direction information for navigation systems. flywheel effect: The characteristic of a parallel LC circuit which permits a continuing flow of current even though only small pulses of energy are applied to the circuit. free electrons: Those electrons so loosely bound in the outer shells of some atoms that they are able to move from atom to atom when an emf is applied to the material. frequency: The number of complete cycles of a periodic pro- cess per second. In electricity the unit of frequency is the hertz frequency modulation (FM): Modulation of a carrier by caus- ing changes in carrier frequency proportional to the amplitude of the modulating signal. frequency multiplier: A circuit designed to double, triple, or quadruple the frequency of a signal by harmonic conversion. fuse: A metal link which melts when overheated by excess cur- rent, used to break an electric circuit whenever the load be- comes excessive. gain: The increase in signal power through a circuit. galvanometer: A device for measuring electric currents. It usually consists of a current-carrying coil which produces a field to react with the field of a permanent magnet. ganged tuning: A mechanical arrangement to permit the simultaneous tuning of two or more circuits. gas-filled tube: An electron tube with gas introduced into the envelope to produce certain desired operating characteristics (see thyraton tube). gate: An electronic switching circuit commonly employed in digital electronics to produce required outputs in response to particuiar inputs. The outputs are either "on" or "off" to pro- duce the binary digits 1 or 0. Also, the control circuit built into various semiconductor devices. gauss (G): The unit of magnetic flux density equal to 1 Mx (line of force) per square centimeter. generator: A rotating machine designed to produce a certain type and quantity of voltage and current. gilbert (Gb): The unit of magnetomotive force; it is equal to approximately 0.768 ampere-turns. gimbal: A mechanism consisting of a pair of rings, one ring pi- voted within the other and the outer ring supported on pivots 90 from the inner-ring pivots. A gyroscope pivoted in the inner ring at right angles to the inner-ring pivots will be free to precess in response to applied external forces. glideslope: A directed radio beam emanating from a glide- slope transmitter located near the runway of an instrumented airport to provide a reference for guiding an airplane vertically to the runway. grid: An element in an electron tube used to regulate or con- trol the flow of electrons from the cathode to the plate. ground: (1) An electrical connection to the earth; (2) a com- mon connecting device for the zero-potential side of the circuits in an elecrical or electronic system; (3) the accidental connection of a hot conductor to the ground (a hot conductor is one whose potential differs from ground potential). ground wave: That portion of a radio wave which travels to the receiver along the surface of the earth. growler: An electromagnetic device which develops a strong alternating field by which armatures may be tested. guidance: The control of missiles or aircraft in flight. gyroscope: A comparatively heavy wheel mounted on a spin- ning axis which is free to rotate about one or both of two axes perpendicular to each other and to the spinning axis. The gyro- scope is used to sense directional changes and to develop sig- nals for operating automatic pilots and inertial guidance systems.

harmonics: Multiples of a base frequency. henry (H): The unit of inductance. It is the amount of induc- tance in a coil which will induce an emf of 1 V in the coil when the current flow is changing at the rate of 1 A/s. hertz (Hz): The unit of frequency. One Hertz is equal to 1 c/s. heterodyne: The process of mixing two frequencies to pro- duce both sum and difference frequencies. The principle is used in superheterodyne receivers. hexode: An electron tube having six active elements. HIG: Hermetically sealed integrating gyro. A gyro mounted in a sealed case with a viscous damping medium. The output is therefore an indication of the total amount of angular displace- ment of the vehicle in which the gyro is installed, rather than the rate of angular displacement. horizontal situation indicator (HSI): A flight instrument that provides the pilot with information regarding heading, course, glideslope deviation, course deviation, and other data regarding aircraft position. horsepower (hp): A common unit of mechanical power. The time rate of work which will raise 550 lb through a vertical dis- tance of 1 ft in 1 s; also 33 000 ft-lb/min. One horsepower is equal to 746 W of electric power. hot-wire meter: An electric instrument for measuring alternat- ing currents. A wire is heated by the current flow, and the ex- pansion of the wire is used to provide movement for the indicating needle. hydrometer: A calibrated float used to determine the specific gravity of a liquid. hypotenuse: The side of a right triangle opposite the right angle. hysteresis: The ability of a magnetic material to withstand changes in its magnetic state. When a magnetomotive force (mmf) is applied to such a material, the magnetization lags the mmf because of a resistance to change in orientation of the par- ticles involved. ignition: Pertaining to engines, the introduction of an electric spark into a combustion chamber to fire the fuel-air mixture. image frequency: The heterodyne action of an oscillator in a superheterodyne receiver. An image frequency is produced when an unwanted signal is of such a frequency that when mixed with the oscillator frequency, it produces a differenece frequency equal to the intermediate frequency of the receiver. impedance (Z): The combined effect of resistance, capacitive reactance, and inductive reactance in an ac circuit. 2 is mea- sured in ohms. inductance: The ability of a coil or conductor to oppose a change in current flow (see henry). inductance coil: A coil designed to introduce inductance into a circuit. induction motor: An ac motor in which the rotating field pro- duced by the stator induces currents and opposing fields in the rotor. The reaction of the fields creates the rotation force. inductive reactance (XL): The effect of inductance in an ac circuit. The formula for inductive reactance is XL = 2 f i . XL is measured in ohms. inductor: An inductance coil. inertia: The tendency of a mass to remain at rest or to con- tinue in motion in the same direction. inertial guidance: The guidance of a missile or airplane by means of a device which senses changes of direction or ac- celeration, and automatically corrects deviations in planned course. instrument landing system (ILS): A radio guidance and communications system designed to guide aircraft through ap- proaches, letdowns, and landings under instrument flying condi- tions.

insulator: A material which will not conduct current to an ap- preciable degree. integrated circuit: A microminiature circuit incorporated on a very small chip of semiconductor material through solid-state technology. A number of circuit elements such as transistors, diodes, resistors, and capacitors are built into the semiconductor chip by means of photography, etching, and diffusion. integrating circuit: A network circuit whose output is propor- tional to the sum of its instantaneous inputs. interelectrode capacitance: The capacitance existing be- tween the electrodes of an electron tube. interpoles: Small magnetic poles inserted between the main field poles of a generator or motor in series with the load circuit to compensate for the effect of armature reaction. inverter: A mechanical or electronic device which converts di- rect current to alternating current. Also, a binary digital circuit element or circuit with one input and one output. The output state is always the inverse (opposite) the input state. ion: An atom or molecule which has lost one or more elec- trons (positive ion) or one which has one or more extra elec- trons (negative ion). ionization: The process of creating ions by either chemical or electrical means. iron-vane movement: An ac electric measuring instrument which depends upon a soft-iron vane or movable core operating with a coil to produce an indication of ac current flow. joule (J): A unit of electric energy or work equivalent to the work done in maintaining a current of 1 A against a resistance of I L? for 1 s; 1 J = 0.73732 ft. Ib. jumper: A short conductor usually used to make a temporary connection between two terminals. junction box: An enclosure used to house and protect termi- nal strips and other circuit components. junction transistor: A transistor consisting of a single crystal of p- or n-type germanium between two electrodes of the opposite type. The center layer is the base and forms junctions with the emitter and collector. Kennelly-Heaviside layer: An ionized layer in the upper at- mosphere which reflects radio waves to earth; also called E layer or ionosphere. keying: The process of modulating a CW carrier wave with a key circuit to provide interruptions in the carrier in the form of dots and dashes for code transmission. kilo: A prefix meaning 1000; e. g., kilocycle, kilovolt, kilowatt, etc. kinetic energy: The energy which a body possesses as a result of its motion. It is equal to 3MV2 where M is mass, and V is veloc- ity. klystron tube: A special electron tube for UHF circuits in which modulation is accomplished by varying the velocity of the electrons flowing through the tube. LC circuit: A circuit network containing inductance and ca- pacitance. Lenz's law: A law stated by H. F. E. Lenz in 1833 to the effect that an induced current in a conductor is always in such a direc- tion that its field opposes the change in the field causing the in- duced current. light-emitting diode (LED): A semiconductor that utilizes a light-producing material such as gallium phosphide. The ma- terial produces light when an electric current is passed through it in a certain direction. LEDs are often used for digital displays. limit switch: A switch designed to stop an actuator at the limit of its movement. load factor: The ratio of average load to greatest load. local oscillator: The internal-oscillator section of a superhe- terodyne circuit.

localizer: That section of an ILS which produces the direc- microwave: An electromagnetic wave with a length ot less tional reference beam. logic circuit: A circuit designed to operate according to the fundamental laws of logic. loop: A control circuit consisting of a sensor, a controller, an actuator, a controlled unit, and a follow-up or feedback to the sensor; also, any closed electronic circuit including a feedback signal which is compared with the reference signal to maintain a desired condition. loop antenna: A bidirectional antenna consisting of one or more complete turns of wire in a coil. loopstick: A loop antenna consisting of a large number of turns of wire wound on a powdered iron (ferrite) rod. Loopsticks are particularly useful in small portable radio receivers. LORAN (Long-RAnge Navigation): A radio navigation sys- tem utilizing master and slave stations transmitting timed pulses. The time difference in reception of pulses from several stations establishes a hyperbolic line of position which may be identified on a LORAN chart. By utilizing signals from two pairs of stations, a fix in position is obtained. low-pass filter: A filter circuit designed to pass LF signals and attenuate HF signals. Mach number: The ratio of actual speed to the speed of sound. An object moving at the speed of sound has a Mach number of 1. Machmeter: An instrument for indicating the speed of a vehi- cle in terms of Mach number. magamp: A contraction of magnetic amplifier. An amplifier system using saturable reactors to control an output to obtain amplification. magnet: A solid material which has the property of attracting magnetic substances. magnetic field: A space where magnetic lines of force exist. magneto: A special type of electric generator having a perma- nent magnet or magnets to provide the field. magnetomotive force (mmf): Magnetizing force, measured in gilberts or ampere-turns. magnetron tube: A special electron tube for use in microwave systems. It uses strong magnetic and electric fields and tuned cavities to produce microwave amplification. marker beacon: A radio navigation aid used in the approach zone of an instrumented airport. As the airplane crosses over the marker-beacon transmitter, the pilot receives an accurate indica- tion of his distance from the runway through the medium of a flashing light and an aural signal. master switch: A switch designed to control all electric power to all circuits in a system. matter: That which has substance and occupies space; ma- terial. maxwell (Mx): A unit of magnetic flux; one magnetic line of force. mega: A prefix denoting one million, e.g., megahertz, meg- ohm, etc. mercury-vapor rectifier: A rectifier tube containing mercury which vaporizes during operation and increases the current-car- rying capacity of the tube. mho: A unit of conductance, the reciprocal of ohm. microfarad (pF): One-millionth of a farad. microphone: A device for converting sound waves to electric impulses. rniscrosecond ( ~ s ) : One-millionth of a second. microprocessor: An integrated circuit (IC) that can be pro- grammed to perform a variety of desired functions. The circuit contains an arithmetic and logic unit, a controlrer, some regis- ters, and possibly other elements.

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than 10 m; i.e., it has a frequency of 30 MHz or more. microwave landing system (MLS): A radio landing system for aircraft that utilizes microwave frequencies for the transmis- sion of guidance and control signals. mil: One-thousandth of an inch. milli: A prefix meaning one-thousandth; e.g., milliammeter, milliampere, millihenry, etc. mixer: A circuit in which two frequencies are combined to produce sum and difference frequencies (see heterodyne and beat frequency oscillator). modulation: The impressing of an information signal on a car- rier wave. modulator: That portion of a transmitter circuit which modu- lates the carrier wave. molecule: The smallest particle of a substance which can exist in a free state and maintain its chemical properties. motor, electric: A rotating device for converting electric en- ergy to mechanical energy. multimeter: A combination instrument designed to measure a variety of electrical quantities. multiplier tube: An electron tube designed to amplify or mul- tiply very weak electron currents by means of secondary emis- sion. multivibrator: A special type of relaxation oscillator circuit de- signed to produce nonlinear signals such as square waves and sawtooth waves. mutual inductance: The inductance of a voltage in one coil due to the field produced by an adjacent coil. Inductive coupling is accomplished through the mutual inductance of two adjacent coils. neutralization: The use of circuits external to electron tubes to cancel the effects of interelectrode capacitance. neutron: A neutral particle found in the nucleus of an atom. north pole: The north-seeking pole of a magnet. nucleus: The core or center particle of an atom. null: An indicated low or zero point in a radio signal. oersted: An mmf of 1 Gb/cm2. ohm (a): The unit of resistance which limits the current to 1 A when an emf of 1 V is applied. ohmmeter: An electric measuring instrument designed to measure resistance in ohms. Ohm's law: A law of current flow stated by George S. Ohm as follows: One volt of electrical pressure is required to force 1 A of current through 1 cR of resistance; also, the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance. The formula for Ohm's law may be expressed I = E/R, R = Ell, or E = IR. optoelectronics: Electronic systems that utilize light-emitting and light-sensitive devices such as light-emitting diodes (LED) and phototransistors for control and operation.

$oscillator: An electronic circuit which produces alternating currents with frequencies determined by the inductance and ca- pacitance in the circuit. oscillograph: A device for producing a graphical representa- tion of an electric signal mechanically or photographically. oscilloscope: An electronic device utilizing a CRT for observ- ing electric signals. parallel circuits: Two or more complete circuits connected to the same two power terminals. peak inverse voltage (PIV): The maximum voltage which may be applied safely to an electron tube or semiconductor device in the direction inverse to normal current flow. peak voltage: The maximum level of a variable voltage.

pentagrid converter: A five-grid electron tube which serves as a mixer, local oscillator, and first detector in a superheterodyne radio receiver. pentode: An electron tube containing five electrodes-cath- ode, plate, control grid, suppressor grid, and screen grid. permeability (p): The property of a magnetic substance de- termining the flux density produced in the substance by a mag- netic field of a given intensity. The formula is p = B /H, where B is flux density in gauss, and H is the field intensity in oersteds. The permeability of air is 1. phase angle: The angular difference between two sinusoidal waveforms. When the voltage of an ac signal leads the current by loo, there is a phase angle of 10" between the voltage and current. phase inverter: An electronic circuit whose output is 180" out of phase with the input. photo cell: An electronic device which becomes conductive or produces a voltage when struck by light. phototransistor: A transistor in which light is used to control the collector-emitter current. picofarad (pF): One-millionth of a microfarad. piezoelectric effect: The property of certain crystals enabling them to generate an electrostatic voltage between opposite faces when subjected to mechanical pressure. Conversely, the crystal will expand or contract if subjected to a strong electrical poten- tial. pitch: The rotation of an airplane or missile about its lateral axis. plan position indicator (PPI): A radar system component for presenting a maplike display of the search area on the screen of a CRT. plate, electron tube: The anode of an electron tube. plate resistance: In an electron tube, the ratio of a change in plate voltage to a change in plate current with grid voltage con- stant; expressed R, = AE,/Ai,. plate saturation: The condition in an electron tube when the plate will no longer attract electrons as fast as they are emitted by the cathode. polarity: (1) The nature of the electric charge on each of two terminals between which there is a potential difference; (2) the difference in the nature of the magnetic effect exhibited by the two poles of a magnet. potential difference (PD): The voltage existing between two terminals or two points of differing potential. potentiometer: A variable resistor often used as a voltage di- vider. power: The rate of doing work (see horsepower). power factor: In ac circuits, a multiplier equal to the cosine of the phase angle (8) between the current and voltage. The power of an ac circuit in watts is equal to El cos 8. power supply: The part of an electronic circuit which supplies the filament and plate voltages for the operation of the circuit. primary cell: A voltaic cell whose chemical action destroys some of the active elements in the cell, thus making it impossible or impractical to recharge. primary winding: The input winding of a transformer. proton: A positively charged particle found in the nucleus of an atom. pulse generator: An electronic circuit designed to produce sharp pulses of voltage. Q factor: The "figure of merit" or "quality" of an inductance coil. The formula for the Q of a coil is Q = XL/R = 271$./R. radar (radio detecting and ranging): Radio equipment which utilizes reflected pulse signals to locate and determine the dis- tance to any reflecting object within its range.

radar mile: The time required for a radar pulse to travel a dis- tance of 1 nmi and return to the radar receiver; approximately 12.4 ps. radio frequency (RF as adjective): All frequencies above the audible range, usually above 20 000 Hz. rate gyro: A gyro unit whose output is proportional to the rate of changing direction. rate signal: Any signal proportional to a rate of change. ratiometer: A measuring instrument in which the movement of the indicator is proportional to the ratio of two currents. RC circuit: A circuit containing both resistance and capaci- tance. RC time constant: The time required to charge a capacitor to 63.2 percent of its full-charge state through a given resistance. rectification: The conversation of alternating current to direct current by means of a rectifier. rectifier: A device which permits current to flow in one direc- tion only. regeneration: Positive feedback of an output signal to the input of an electronic-tube to increase the power of a signal. relaxation oscillator: An oscillator circuit in which an RC cir- cuit determines frequency of oscillation. The output is a saw- tooth or rectangular wave. relay: An electric switch operated by an electromagnet or sole- noid. reluctance: The property of a material which opposes the pas- sage of magnetic flux lines through it. resistor: A circuit element possessing a finite amount of resist- ance. resonance: A condition in an LC circuit in which capacitive reactance and inductive reactance are equal. reverse-current relay: A relay incorporated into a generator circuit to disconnect the generator from the battery when battery voltage is greater than generator voltage. rheostat: A variable resistor. ripple: A small periodic variation in the voltage level of a dc power supply. roll: The rotation of an airplane or missile about its longitudinal axis. rotor: A rotating part of an electric machine. sawtooth wave: The output of a relaxation oscillator, rising slowly and then dropping sharply to zero to form waveshapes resembling sawteeth. scope: A contraction of oscilloscope. Also used to designate the CRT used in radar. screen grid: A grid constructed of fine wire mesh placed be- tween the control grid and plate in an electron tube to reduce the effects of grid-plate capacitance. secondary cell: An electrolytic voltaic cell capable of being re- peatedly charged and discharged. secondary coil: The output winding of a transformer.

secondary emission: The emission of electrons from a surface when struck by high-velocity electrons from the cathode. Selcal: A contraction of selective calling referring to an auto- matic signaling system used in aircraft to notify the pilot that the aircraft is receiving a call. selectivity: The ability of a radio receiver to tune in desired signals and tune out undesired signals. selenium rectifier: A rectifier using a thin coating of selenium on an iron disk to develop a unidirectional current-carrying characteristic. Electrons flow easily from the iron to the selenium but encounter high resistance in the opposite direction. A metal alloy is used in order to form the electrical. connection with the selenium.

self-inductance: The property of a single conductor or a coil causing it to induce a voltage in itself whenever there is a change of current flow. Selsyn: A trade name of the General Electric Company ap- plied to self-synchronizing units or synchros. semiconductor controlled rectifier (SCR): A semiconductor rectifier that is controlled by means of a gate signal. sensitivity: A measure of the ability of a radio receiver to re- ceive very weak signals. sensor: A sensing unit used to actuate signal-producing de- vices in response to changes in physical conditions. series circuit: A circuit in which the current flows through all the circuit elements via a single path. servo: An actuating device which feeds back an indication of its output or movement to the controlling unit, where it is com- pared with a reference at the input. Any difference between the input and output is used to produce the required control. shielding: Metal covers placed around electric and electronic devices to prevent the intrusion of external electrostatic and electromagnetic fields. shunt: A calibrated resistor connected across an electric de- vice to bypass a portion of the current. side bands: The bands of frequencies on each side of carrier frequency produced by modulation. signal: The electric current, voltage, or waves constituting the inputs and outputs of electric or electronic circuits or devices. A signal may be the electric energy carrying information or may be the information itself. signal generator: A test unit designed to produce reference electric signals which may be applied to electronic circuits for testing purposes. sine curve or wave: A graphical representation of a wave pro- portional in magnitude to the sine of its angular displacement; hence, the sine wave is most useful in representing ac values. skin effect: The tendency of HF alternating currents to flow in the outer portion of a conductor. skip distance: The distance from a transmitter to the point where the reflected sky wave first reaches the earth. sky wave: That portion of a radio wave which is reflected from the ionosphere. slip rings: Conducting rings used with brushes to conduct electric current to or from a rotating unit. solenoid: An electromagnetic device having a movable core. space charge: The electric charge carried by the cloud of electrons in the space between electrodes of an electron tube. split-phase motor: An ac motor which utilizes an inductor or capacitor to shift the phase of the current in one of two field windings. This causes the resultant field to have a rotational ef- fect. square mil (mil2): An area equivalent to a square having sides 1 mil (0.001 in) in length. square wave: An electric wave having a square shape. standing waves: Stationary waves occurring on an antenna or transmission line as a result of two waves, identical in amplitude and frequency, traveling in opposite directions along the con- ductor. stator: The stationary winding of a rotating ac machine. substrate: The semiconductor material upon which diffused and epitaxially deposited regions are formed to construct diodes, transistors and similar devices. superheterodyne: A radio receiver using the heterodyne prin- ciple to produce an intermediate frequency (IF). suppressor grid: A grid placed between the screen grid and the plate in an electron tube to cause secondary electrons to re- turn to the plate.

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susceptance: The ratio of the effective current to the effective voltage in an ac circuit multiplied by the sine of the phase differ- ence between the current and voltage. sweep: The horizontal deflection of the electron beam in a CRT. switch: A device for opening and closing electric circuits. synchro: A device for transmitting indications of angular posi- tion from one point to another. synchronous motor: An ac motor whose rotor is synchro- nized with the rotating field produced by the stator. The speed of rotation is always in time with the frequency of the applied alter- nating current. synchroscope: An instrument designed to show whether two rotating elements are in synchronization. tachometer: An instrument designed to indicate the rpm of a rotating device. tank circuit: A parallel resonant circuit including an induc- tance and a capacitance. telemetering: A system of sending measurements over great distances by radio. terminal: A connecting fitting attached to the end of a circuit element. terminal strip: An insulated strip with terminal posts to pro- vide a convenient junction point for a group of separate circuits. tetrode: An electron tube or semiconductor device containing four active electrodes. thermionic: A term describing electron emission caused by heat. thermocouple: A junction of two dissimilar metals which gen- erates a small current when exposed to heat. three-phase system: An ac electric system consisting of three conductors, each cartying a current 120" out of phase with each other. Three-phase systems are used extensively in modem electric and electronic actuating systems. thyratron tube: A triode tube into which a gas has been intro- duced to change its operating characteristics. The control grid in a thyratron tube is used to start conduction when the correct po- tential difference exists between the cathode and plate. After the tube starts to conduct, the control grid is no longer effective, and the tube will continue to conduct even though the cathode-plate voltage drops very low. thyristor: A four-layer (pnpn) semiconductor device with two, three, or four external terminals. Current flow through a thyris- tor may be controlled by one or more gates, by light, or by volt- age applied between the two main terminals. transconductance (GY): The ratio of a small change in plate current to a small change in grid voltage. The formula is G M = I,/E, (plate voltage constant). transformer: A device used to couple electric energy between circuits by means of mutual inductance. transistor: A semiconductor device, usually made of a ger- manium or silicon crystal, used to rectify or amplify an electric signal. transmission line: A conductor for radio waves, usually used to conduct RF energy from the output of a transmitter to the an- tenna. transmitter: An electronic system designed to produce modu- lated RF camer waves to be radiated by the antenna; also, elec- tric devices used to collect quantitative information at one point and send it to a remote indicator electrically. triac: A thyristor that provides bilateral operation. It is equiva- lent to two silicon-controlled rectifiers in inverse parallel connec- tion. It is described as a bidirectional triode thyristor and is controlled by a gate circuit. trigger pulse: An electric pulse applied to certain electronic circuit elements to start an operation.

trimmer capacitor: A low-capacity, adjustable capacitor con- nected in parallel with a large capacitor to provide fine tuning adjustments. triode: An electron tube or semiconductor device with three active electrodes. tuned radio frequency (TRF) receiver: A radio receiver in which tuning and amplification are accomplished in the RF sec- tion before the signal reaches the detector. After the detector one or more stages of AF amplification are employed to increase the output sufficiently to operate a loudspeaker. tungar rectifier: A high-capacity diode rectifier tube having a heated cathode and a graphite plate in an envelope filled with argon gas. tuning: The process of adjusting circuits to resonance at a par- ticular fiequency. turn-and-bank indicator: A gyro-operated instrument de- signed to show the pilot of an airplane the rate of turn. It also has a curved tube containing a ball to show whether the airplane is correctly banked. ultrahigh frequency (UHF): Radio frequencies between 300 and 3000 MHz. vacuum tube: An electron tube with an evacuated envelope. vacuum-tube voltmeter (VTVM): An electronic voltage-mea- suring instrument used for electronic circuit testing. Its ve y high input impedance prevents it from drawing appreciable power from the circuit being tested. variable-mu ( p ) tube: An electron tube having a control grid in which the grid wires are spaced less closely at the center than at the ends. This causes the amplification factor to change as gnd bias is changed. Also called a remote-cutoff tube. vector: A quantity having both magnitude and direction. velocity: A measure of speed with direction. very high frequency (VHF): The frequency range between 30 and 300 MHz. very low frequency (VLF): The frequency range between 3 and 30 kHz. VHF omnirange (VOR): An electronic air navigation system which provides accurate direction information in relation to a certain ground station.

video: A term describing electronic circuit components con- trolling or producing the visual signals displayed on a CRT. volt: The unit of emf or voltage. volt-amperes: The product of the voltage and current in a cir- cuit. voltage divider: A resistance arranged with connections (taps) to provide for the removal of voltages of any desired level. A po- tentiometer is often used as a variable voltage divider. voltage regulator: A circuit which maintains a constant level voltage supply despite changes in input voltage or load. voltmeter: A voltage-measuring instrument. volume control: The circuit in a receiver or amplifier which varies loudness. watt (W): The unit of electric power. In a dc circuit, power (in watts) = volts x amperes, or P ( W ) = El. watthour (Wh): The commercial unit of electric energy; watt- hours = watts x hours. wattmeter: An instrument designed to measure electric power. waveguide: A hollow metal tube designed to carry electro- magnetic energy at extremely high frequencies. waveIength (A): The distance between points of identical phase in a radio wave. The formula for wavelength is A (lambda) = 300 000 000/f where h is wavelength in meters, and f is frequency in hertz. Weston meter movement: A moving-coil instrument move- ment. Wheatstone bridge: A bridge circuit consisting of three known resistances, one unknown resistance, and a galvanome- ter. The indication shown by the galvanometer is used to deter- mine the value of the unknown resistance. yaw: Rotation of an airplane or missile about its vertical axis; turning to the right or left. zener diode: A diode rectifier designed to prevent the flow of current in a reverse direction until the voltage in that direction reaches a predetermined value. At this time the diode permits a reverse current to flow.