Chapter XXIV: Appendix: Useful Information (1)

ABBREVIATIONS OF UNITS

Unit Abbreviation

ampere amp. ampere-hours amp.-hr. centimeter cm. centimeter-gram-second c.g.s. cubic centimeters cm.^3 cubic inches cu. in. cycles per second ~ degrees Centigrade °C. degrees Fahrenheit °F. feet ft. foot-pounds ft.-lb. grams g. henries h. inches in. kilograms kg. kilometers km. kilowatts kw. kilowatt-hours kw.-hr. kilovolt-amperes kv.-a. meters m. microfarads [Greek: mu]f. micromicrofarads [Greek: mu mu]f. millihenries mh. millimeters mm. pounds lb. seconds sec. square centimeters cm.^2 square inches sq. in. volts v. watts w.

PREFIXES USED WITH METRIC SYSTEM UNITS

Prefix Abbreviation Meaning

micro [Greek: mu]. 1 millionth milli m. 1 thousandth centi c. 1 hundredth deci d. 1 tenth deka dk. 10 hekto h. 1 hundred kilo k. 1 thousand mega m. 1 million

SYMBOLS USED FOR VARIOUS QUANTITIES

Quantity Symbol

capacitance C

conductance g

coupling co-efficient k

current, instantaneous i

current, effective value I

decrement [Greek: delta]

dielectric constant [Greek: alpha]

electric field intensity [Greek: epsilon]

electromotive force, instantaneous value E

electromotive force, effective value F

energy W

force F

frequency f

frequency x 2[Greek: pi] [Greek: omega]

impedance Z

inductance, self L

inductance, mutual M

magnetic field intensity A

magnetic flux [Greek: Phi]

magnetic induction B

period of a complete oscillation T

potential difference V

quantity of electricity Q

ratio of the circumference of a circle to its diameter =3.1416 [Greek: pi]

reactance X

resistance R

time t

velocity v

velocity of light c

wave length [Greek: lambda]

wave length in meters [Greek: lambda]m

work W

permeability [Greek: mu]

Square root [Math: square root]

TABLE OF ENAMELED WIRE

No. of Turns Turns Ohms per
Wire, per per Cubic Inch
B.& S. Linear Square of
Gauge Inch Inch Winding

20 30 885 .748

22 37 1400 1.88

24 46 2160 4.61

26 58 3460 11.80

28 73 5400 29.20

30 91 8260 70.90

32 116 21,000 7547.00

34 145 13,430 2968.00

36 178 31,820 1098.00

38 232 54,080 456.00

40 294 86,500 183.00

TABLE OF FREQUENCY AND WAVE LENGTHS

W. L.--Wave Lengths in Meters.
F.--Number of Oscillations per Second.
O. or square root L. C. is called Oscillation Constant.
C.--Capacity in Microfarads.
L.--Inductance in Centimeters.
1000 Centimeters = 1 Microhenry.

W.L. F O L.C.
50 6,000,000 .839 .7039
100 3,000,000 1.68 2.82
150 2,000,000 2.52 6.35
200 1,500,000 3.36 11.29
250 1,200,000 4.19 17.55
300 1,000,000 5.05 25.30
350 857,100 5.87 34.46
400 750,000 6.71 45.03
450 666,700 7.55 57.00
500 600,000 8.39 70.39
550 545,400 9.23 85.19
600 500,000 10.07 101.41
700 428,600 11.74 137.83
800 375,000 13.42 180.10
900 333,300 15.10 228.01
1,000 300,000 16.78 281.57
1,100 272,730 18.45 340.40
1,200 250,000 20.13 405.20
1,300 230,760 21.81 475.70
1,400 214,380 23.49 551.80
1,500 200,000 25.17 633.50
1,600 187,500 26.84 720.40
1,700 176,460 28.52 813.40
1,800 166,670 30.20 912.00
1,900 157,800 31.88 1,016.40
2,000 150,000 33.55 1,125.60
2,100 142,850 35.23 1,241.20
2,200 136,360 36.91 1,362.40
2,300 130,430 38.59 1,489.30
2,400 125,000 40.27 1,621.80
2,500 120,000 41.95 1,759.70
2,600 115,380 43.62 1,902.60
2,700 111,110 45.30 2,052.00
2,800 107,140 46.89 2,207.00
2,900 103,450 48.66 2,366.30
3,000 100,000 50.33 2,533.20
4,000 75,000 67.11 4,504.00
5,000 60,000 83.89 7,038.00
6,000 50,000 100.7 10,130.00
7,000 41,800 117.3 13,630.00
8,000 37,500 134.1 18,000.00
9,000 33,300 151.0 22,820.00
10,000 30,000 167.9 28,150.00
11,000 27,300 184.8 34,150.00
12,000 25,000 201.5 40,600.00
13,000 23,100 218.3 47,600.00
14,000 21,400 235.0 55,200.00
15,000 20,000 252.0 63,500.00
16,000 18,750 269.0 72,300.00

PRONUNCIATION OF GREEK LETTERS

Many of the physical quantities use Greek letters for symbols. The following is the Greek alphabet with the way the letters are pronounced:

a alpha
b beta
g gamma
d delta
e epsilon
z zeta
ae eta
th theta
i iota
k kappa
l lambda
m mu
n nu
x Xi(Zi)
o omicron
p pi
r rho
s sigma
t tau
u upsilon
ph phi
ch chi
ps psi
o omega

TABLE OF SPARKING DISTANCES

In Air for Various Voltages between Needle Points

Volts Distance
Inches Centimeter
5,000 .225 .57
10,000 .470 1.19
15,000 .725 1.84
20,000 1.000 2.54
25,000 1.300 3.30
30,000 1.625 4.10
35,000 2.000 5.10
40,000 2.450 6.20
45,000 2.95 7.50
50,000 3.55 9.90
60,000 4.65 11.8
70,000 5.85 14.9
80,000 7.10 18.0
90,000 8.35 21.2
100,000 9.60 24.4
110,000 10.75 27.3
120,000 11.85 30.1
130,000 12.95 32.9
140,000 13.95 35.4
150,000 15.00 38.1

FEET PER POUND OF INSULATED MAGNET WIRE

No. of Single Double Single Double
B.& S. Cotton, Cotton, Silk, Silk, Enamel
Gauge 4-Mils 8-Mils 1-3/4-Mils 4-Mils

20 311 298 319 312 320
21 389 370 408 389 404
22 488 461 503 498 509
23 612 584 636 631 642
24 762 745 800 779 810
25 957 903 1,005 966 1,019
26 1,192 1,118 1,265 1,202 1,286
27 1,488 1,422 1,590 1,543 1,620
28 1,852 1,759 1,972 1,917 2,042
29 2,375 2,207 2,570 2,435 2,570
30 2,860 2,534 3,145 2,900 3,240
31 3,800 2,768 3,943 3,683 4,082
32 4,375 3,737 4,950 4,654 5,132
33 5,590 4,697 6,180 5,689 6,445
34 6,500 6,168 7,740 7,111 8,093
35 8,050 6,737 9,600 8,584 10,197
36 9,820 7,877 12,000 10,039 12,813
37 11,860 9,309 15,000 10,666 16,110
38 14,300 10,636 18,660 14,222 20,274
39 17,130 11,907 23,150 16,516 25,519
40 21,590 14,222 28,700 21,333 32,107

INTERNATIONAL MORSE CODE AND CONVENTIONAL SIGNALS

TO BE USED FOR ALL GENERAL PUBLIC SERVICE RADIO COMMUNICATION

1. A dash is equal to three dots.

2. The space between parts of the same letter is equal to one dot.

3. The space between two letters is equal to three dots.

4. The space between two words is equal to five dots.

[Note: period denotes Morse dot, hyphen denotes Morse dash]

A .-

B -...

C -.-.

D -..

E .

F ..-.

G --.

H ....

I ..

J .---

K -.-

L .-..

M --

N -.

O ---

P .--.

Q --.-

R .-.

S ...

T -

U ..-

V ...-

W .--

X -..-

Y -.--

Z --..

Ä (German) .-.-

Á or Å (Spanish-Scandinavian) .--.-

CH (German-Spanish) ----

É (French) ..-..

Ñ (Spanish) --.--

Ö (German) ---.

Ü (German) ..--

1 .----

2 ..---

3 ...--

4 ....-

5 .....

6 -....

7 --...

8 ---..

9 ----.

0 -----

Period .. .. ..

Semicolon -.-.-.

Comma -.-.-.

Colon ---...

Interrogation ..--..

Exclamation point --..--

Apostrophe .----.

Hyphen -....-

Bar indicating fraction -..-.

Parenthesis -.--.-

Inverted commas .-..-.

Underline ..--.-

Double dash -...-

Distress Call ...---...

Attention call to precede every transmission -.-.-

General inquiry call -.-. --.-

From (de) -.. .

Invitation to transmit (go ahead) -.-

Warning--high power --..--

Question (please repeat after ...)--interrupting long messages ..--..

Wait .-...

Break (Bk.) (double dash) -...-

Understand ...-.

Error ........

Received (O.K.) .-.

Position report (to precede all position messages) - .-.

End of each message (cross) .-.-.

Transmission finished (end of work) (conclusion of correspondence) ...-.-

INTERNATIONAL RADIOTELEGRAPHIC CONVENTION

LIST OF ABBREVIATIONS TO BE USED IN RADIO COMMUNICATION

ABBREVIATION QUESTION ANSWER OR REPLY

PRB Do you wish to communicate I wish to communicate by means
by means of the International of the International Signal Code.
Signal Code?

QRA What ship or coast station is This is....
that?

QRB What is your distance? My distance is....

QRC What is your true bearing? My true bearing is....

QRD Where are you bound for? I am bound for....

QRF Where are you bound from? I am bound from....

QRG What line do you belong to? I belong to the ... Line.

QRH What is your wave length in My wave length is ... meters.
meters?

QRJ How many words have you to send? I have ... words to send.

QRK How do you receive me? I am receiving well.

QRL Are you receiving badly? I am receiving badly. Please
Shall I send 20? send 20.
...-. ...-.
for adjustment? for adjustment.

QRM Are you being interfered with? I am being interfered with.

QRN Are the atmospherics strong? Atmospherics are very strong.

QRO Shall I increase power? Increase power.

QRP Shall I decrease power? Decrease power.

QRQ Shall I send faster? Send faster.

QRS Shall I send slower? Send slower.

QRT Shall I stop sending? Stop sending.

QRU Have you anything for me? I have nothing for you.

QRV Are you ready? I am ready. All right now.

QRW Are you busy? I am busy (or: I am busy with...).
Please do not interfere.

QRX Shall I stand by? Stand by. I will call you when
required.

QRY When will be my turn? Your turn will be No....

QRZ Are my signals weak? You signals are weak.

QSA Are my signals strong? You signals are strong.

QSB Is my tone bad? The tone is bad.
Is my spark bad? The spark is bad.

QSC Is my spacing bad? Your spacing is bad.

QSD What is your time? My time is....

QSF Is transmission to be in Transmission will be in
alternate order or in series? alternate order.

QSG Transmission will be in a
series of 5 messages.

QSH Transmission will be in a
series of 10 messages.

QSJ What rate shall I collect for...? Collect....

QSK Is the last radiogram canceled? The last radiogram is canceled.

QSL Did you get my receipt? Please acknowledge.

QSM What is your true course? My true course is...degrees.

QSN Are you in communication with land? I am not in communication with land.

QSO Are you in communication with I am in communication with...
any ship or station (through...).
(or: with...)?

QSP Shall I inform...that you are Inform...that I am calling him.
calling him?

QSQ Is...calling me? You are being called by....

QSR Will you forward the radiogram? I will forward the radiogram.

QST Have you received the general General call to all stations.
call?

QSU Please call me when you have Will call when I have finished.
finished (or: at...o'clock)?

QSV Is public correspondence being Public correspondence is being
handled? handled. Please do not interfere.

[Footnote: Public correspondence is any radio work, official or private, handled on commercial wave lengths.]

QSW Shall I increase my spark Increase your spark frequency.
frequency?

QSX Shall I decrease my spark Decrease your spark frequency.
frequency?

QSY Shall I send on a wavelength Let us change to the wave length
of ... meters? of ... meters.

QSZ Send each word twice. I have
difficulty in receiving you.

QTA Repeat the last radiogram.

When an abbreviation is followed by a mark of interrogation, it refers to the question indicated for that abbreviation.

Useful Information

Symbols Used For Apparatus

alternator

ammeter

aerial

arc

battery

buzzer

condenser

variable condenser

connection of wires

no connection

coupled coils

variable coupling

detector

gap, plain

gap, quenched

ground

hot wire ammeter

inductor

variable inductor

key

resistor

variable resistor

switch s.p.s.t.

" s.p.d.t.

" d.p.s.t.

" d.p.d.t.

" reversing

phone receiver

" transmitter

thermoelement

transformer

vacuum tube

voltmeter

choke coil

DEFINITIONS OF ELECTRIC AND MAGNETIC UNITS

The _ohm_ is the resistance of a thread of mercury at the temperature of melting ice, 14.4521 grams in mass, of uniform cross-section and a length of 106.300 centimeters.

The _ampere_ is the current which when passed through a solution of nitrate of silver in water according to certain specifications, deposits silver at the rate of 0.00111800 of a gram per second.

The _volt_ is the electromotive force which produces a current of 1 ampere when steadily applied to a conductor the resistance of which is 1 ohm.

The _coulomb_ is the quantity of electricity transferred by a current of 1 ampere in 1 second.

The _ampere-hour_ is the quantity of electricity transferred by a current of 1 ampere in 1 hour and is, therefore, equal to 3600 coulombs.

The _farad_ is the capacitance of a condenser in which a potential difference of 1 volt causes it to have a charge of 1 coulomb of electricity.

The _henry_ is the inductance in a circuit in which the electromotive force induced is 1 volt when the inducing current varies at the rate of 1 ampere per second.

The _watt_ is the power spent by a current of 1 ampere in a resistance of 1 ohm.

The _joule_ is the energy spent in I second by a flow of 1 ampere in 1 ohm.

The _horse-power_ is used in rating steam machinery. It is equal to 746 watts.

The _kilowatt_ is 1,000 watts.

The units of capacitance actually used in wireless work are the _microfarad_, which is the millionth part of a farad, because the farad is too large a unit; and the _C. G. S. electrostatic unit of capacitance_, which is often called the _centimeter of capacitance_, which is about equal to 1.11 microfarads.

The units of inductance commonly used in radio work are the _millihenry_, which is the thousandth part of a henry; and the _centimeter of inductance_, which is one one-thousandth part of a microhenry.

Note.--For further information about electric and magnetic units get the _Bureau of Standards Circular No. 60_, called _Electric Units and Standards_, the price of which is 15 cents; also get _Scientific Paper No. 292_, called _International System of Electric and Magnetic Units_, price 10 cents. These and other informative papers can be had from the _Superintendent of Documents, Government Printing Office_, Washington, D. C.

WIRELESS BOOKS

The Admiralty Manual of Wireless Telegraphy. 1920. Published by His Majesty's Stationery Office, London.

Ralph E. Batcher.--Prepared Radio Measurements. 1921. Wireless Press, Inc., New York City.

Elmer E. Bucher.--Practical Wireless Telegraphy. 1918. Wireless Press, Inc., New York City.

Elmer E. Bucher.--Vacuum Tubes in Wireless Communication. 1919. Wireless Press, Inc., New York City.

Elmer E. Bucher.--The Wireless Experimenter's Manual. 1920. Wireless Press, Inc., New York City.

A. Frederick Collins.--Wireless Telegraphy, Its History, Theory, and Practice. 1905. McGraw Pub. Co., New York City.

J. H. Dellinger.--Principles Underlying Radio Communication. 1921. Signal Corps, U. S. Army, Washington, D. C.

H. M. Dorsett.--Wireless Telegraphy and Telephony. 1920. Wireless Press, Ltd., London.

J. A. Fleming.--Principles of Electric Wave Telegraphy. 1919. Longmans, Green and Co., London.

Charles B. Hayward.--How to Become a Wireless Operator. 1918. American Technical Society, Chicago, Ill.

G. D. Robinson.--Manual of Radio Telegraphy and Telephony. 1920. United States Naval Institute, Annapolis, Md.

Rupert Stanley.--Textbook of Wireless Telegraphy. 1919. Longmans, Green and Co., London.

E. W. Stone.--Elements of Radio Telegraphy. 1919. D, Van Nostrand Co., New York City.

L. B. Turner.--Wireless Telegraphy and Telephony. 1921. Cambridge University Press. Cambridge, England.

Send to the _Superintendent of Documents, Government Printing Office_, Washington, D. C., for a copy of _Price List No. 64_ which lists the Government's books and pamphlets on wireless. It will be sent to you free of charge.

The Government publishes; (1) _A List of Commercial Government and Special Wireless Stations_, every year, price 15 cents; (2) _A List of Amateur Wireless Stations_, yearly, price 15 cents; (3) _A Wireless Service Bulletin_ is published monthly, price 5 cents a copy, or 25 cents yearly; and (4) _Wireless Communication Laws of the United States_, the _International Wireless Telegraphic Convention and Regulations Governing Wireless Operators and the Use of Wireless on Ships and Land Stations_, price 15 cents a copy. Orders for the above publications should be addressed to the _Superintendent of Documents, Government Printing Office, Washington, D. C._

Manufacturers and Dealers in Wireless Apparatus and Supplies:

Adams-Morgan Co., Upper Montclair, N. J.

American Hard Rubber Co., 11 Mercer Street, New York City.

American Radio and Research Corporation, Medford Hillside, Mass.

Brach (L. S.) Mfg. Co., 127 Sussex Ave., Newark, N. J.

Brandes (C.) Inc., 237 Lafayette St., New York City.

Bunnell (J. H.) Company, Park Place, New York City.

Burgess Battery Company, Harris Trust Co. Bldg., Chicago, Ill.

Clapp-Eastman Co., 120 Main St., Cambridge, Mass.

Connecticut Telephone and Telegraph Co., Meriden, Conn.

Continental Fiber Co., Newark, Del.

Coto-Coil Co., Providence, R. I.

Crosley Mfg. Co., Cincinnati, Ohio.

Doolittle (F. M.), 817 Chapel St., New Haven, Conn.

Edelman (Philip E.), 9 Cortlandt St., New York City.

Edison Storage Battery Co., Orange, N. J.

Electric Specialty Co., Stamford, Conn.

Electrose Mfg. Co., 60 Washington St., Brooklyn, N. Y.

General Electric Co., Schenectady, N. Y.

Grebe (A. H.) and Co., Inc., Richmond Hill, N. Y. C.

International Brass and Electric Co., 176 Beekman St., New York City.

International Insulating Co., 25 West 45th St., New York City.

King Amplitone Co., 82 Church St., New York City.

Kennedy (Colin B.) Co., Rialto Bldg., San Francisco, Cal.

Magnavox Co., Oakland, Cal.

Manhattan Electrical Supply Co., Park Place, N. Y.

Marshall-Gerken Co., Toledo, Ohio.

Michigan Paper Tube and Can Co., 2536 Grand River Ave., Detroit, Mich.

Murdock (Wm. J.) Co., Chelsea, Mass.

National Carbon Co., Inc., Long Island City, N. Y.

Pittsburgh Radio and Appliance Co., 112 Diamond St., Pittsburgh, Pa,

Radio Corporation of America, 233 Broadway, New York City.

Riley-Klotz Mfg. Co., 17-19 Mulberry St., Newark, N. J.

Radio Specialty Co., 96 Park Place, New York City.

Roller-Smith Co., 15 Barclay St., New York City.

Tuska (C. D.) Co., Hartford, Conn.

Western Electric Co., Chicago, Ill.

Westinghouse Electric Co., Pittsburgh, Pa.

Weston Electrical Instrument Co., 173 Weston Ave., Newark, N. J.

Westfield Machine Co., Westfield, Mass.

ABBREVIATIONS OF COMMON TERMS

A. ..............Aerial

A.C. ............Alternating Current

A.F. ............Audio Frequency

B. and S. .......Brown & Sharpe Wire Gauge

C. ..............Capacity or Capacitance

C.G.S. ..........Centimeter-Grain-Second

Cond. ...........Condenser

Coup. ...........Coupler

C.W. ............Continuous Waves

D.C. ............Direct Current

D.P.D.T. ........Double Point Double Throw

D.P.S.T. ........Double Point Single Throw

D.X. ............Distance

E. ..............Short for Electromotive Force (Volt)

E.M.F. ..........Electromotive Force

F. ..............Filament or Frequency

G. ..............Grid

Gnd. ............Ground

I. ..............Current Strength (Ampere)

I.C.W. ..........Interrupted Continuous Waves

KW. .............Kilowatt

L. ..............Inductance

L.C. ............Loose Coupler

Litz. ...........Litzendraht

Mfd. ............Microfarad

Neg. ............Negative

O.T. ............Oscillation Transformer

P. ..............Plate

Prim. ...........Primary

Pos. ............Positive

R. ..............Resistance

R.F. ............Radio Frequency

Sec. ............Secondary

S.P.D.T. ........Single Point Double Throw

S.P.S.T. ........Single Point Single Throw

S.R. ............Self Rectifying

T. ..............Telephone or Period (time) of Complete
Oscillation

Tick. ...........Tickler

V. ..............Potential Difference

Var. ............Variometer

Var. Cond. ......Variable Condenser

V.T. ............Vacuum Tube

W.L. ............Wave Length

X. ..............Reactance

GLOSSARY

A BATTERY.--See Battery A.

ABBREVIATIONS, CODE.--Abbreviations of questions and answers used in wireless communication. The abbreviation _of a question_ is usually in three letters of which the first is Q. Thus Q R B is the code abbreviation of "_what is your distance?_" and the answer "_My distance is_..." See Page 306 [Appendix: List of Abbreviations].

ABBREVIATIONS, UNITS.--Abbreviations of various units used in wireless electricity. These abbreviations are usually lower case letters of the Roman alphabet, but occasionally Greek letters are used and other signs. Thus _amperes_ is abbreviated _amp., micro_, which means _one millionth_, [Greek: mu], etc. See Page 301 [Appendix: Useful Abbreviations].

ABBREVIATIONS OF WORDS AND TERMS.--Letters used instead of words and terms for shortening them up where there is a constant repetition of them, as _A.C._ for _alternating current; C.W._ for _continuous waves; V.T._ for _vacuum tube_, etc. See Page 312 [Appendix: Abbreviations of Common Terms].

AERIAL.--Also called _antenna_. An aerial wire. One or more wires suspended in the air and insulated from its supports. It is the aerial that sends out the waves and receives them.

AERIAL, AMATEUR.--An aerial suitable for sending out 200 meter wave lengths. Such an aerial wire system must not exceed 120 feet in length from the ground up to the aerial switch and from this through the leading-in wire to the end of the aerial.

AERIAL AMMETER.--See _Ammeter, Hot Wire_.

AERIAL, BED-SPRINGS.--Where an outdoor aerial is not practicable _bed-springs_ are often made to serve the purpose.

AERIAL CAPACITY.--See _Capacity, Aerial._

AERIAL COUNTERPOISE.--Where it is not possible to get a good ground an _aerial counterpoise_ or _earth capacity_ can be used to advantage. The counterpoise is made like the aerial and is supported directly under it close to the ground but insulated from it.

AERIAL, DIRECTIONAL.--A flat-top or other aerial that will transmit and receive over greater distances to and from one direction than to and from another.

AERIAL, GROUND.--Signals can be received on a single long wire when it is placed on or buried in the earth or immersed in water. It is also called a _ground antenna_ and an _underground aerial._

AERIAL, LOOP.--Also called a _coil aerial, coil antenna, loop aerial, loop antenna_ and when used for the purpose a _direction finder_. A coil of wire wound on a vertical frame.

AERIAL RESISTANCE.--See _Resistance, Aerial._

AERIAL SWITCH.--See _Switch Aerial._

AERIAL WIRE.--(1) A wire or wires that form the aerial. (2) Wire that is used for aerials; this is usually copper or copper alloy.

AERIAL WIRE SYSTEM.--An aerial and ground wire and that part of the inductance coil which connects them. The open oscillation circuit of a sending or a receiving station.

AIR CORE TRANSFORMER.--See _Transformer, Air Core._

AMATEUR AERIAL OR ANTENNA.--See _Aerial, Amateur._

ALTERNATOR.--An electric machine that generates alternating current.

ALPHABET, INTERNATIONAL CODE.--A modified Morse alphabet of dots and dashes originally used in Continental Europe and, hence, called the _Continental Code_. It is now used for all general public service wireless communication all over the world and, hence, it is called the _International Code_. See page 305 [Appendix: International Morse Code].

ALTERNATING CURRENT (_A.C._)--See _Current._

ALTERNATING CURRENT TRANSFORMER.--See _Transformer_.

AMATEUR GROUND.--See _Ground, Amateur_.

AMMETER.--An instrument used for measuring the current strength, in terms of amperes, that flows in a circuit. Ammeters used for measuring direct and alternating currents make use of the _magnetic effects_ of the currents. High frequency currents make use of the _heating effects_ of the currents.

AMMETER, HOT-WIRE.--High frequency currents are usually measured by means of an instrument which depends on heating a wire or metal strip by the oscillations. Such an instrument is often called a _thermal ammeter_, _radio ammeter_ and _aerial ammeter_.

AMMETER, AERIAL.--See _Ammeter, Hot Wire_.

AMMETER, RADIO.--See _Ammeter, Hot Wire_.

AMPERE.--The current which when passed through a solution of nitrate of silver in water according to certain specifications, deposits silver at the rate of 0.00111800 of a gram per second.

AMPERE-HOUR.--The quantity of electricity transferred by a current of 1 ampere in 1 hour and is, therefore, equal to 3600 coulombs.

AMPERE-TURNS.--When a coil is wound up with a number of turns of wire and a current is made to flow through it, it behaves like a magnet. B The strength of the magnetic field inside of the coil depends on (1) the strength of the current and (2) the number of turns of wire on the coil. Thus a feeble current flowing through a large number of turns will produce as strong a magnetic field as a strong current flowing through a few turns of wire. This product of the current in amperes times the number of turns of wire on the coil is called the _ampere-turns_.

AMPLIFICATION, AUDIO FREQUENCY.--A current of audio frequency that is amplified by an amplifier tube or other means.

AMPLIFICATION, CASCADE.--See _Cascade Amplification_.

AMPLIFICATION, RADIO FREQUENCY.--A current of radio frequency that is amplified by an amplifier tube or other means before it reaches the detector.

AMPLIFICATION, REGENERATIVE.--A scheme that uses a third circuit to feed back part of the oscillations through a vacuum tube and which increases its sensitiveness when used as a detector and multiplies its action as an amplifier and an oscillator.

AMPLIFIER, AUDIO FREQUENCY.--A vacuum tube or other device that amplifies the signals after passing through the detector.

AMPLIFIER, MAGNETIC.--A device used for controlling radio frequency currents either by means of a telegraph key or a microphone transmitter. The controlling current flows through a separate circuit from that of the radio current and a fraction of an ampere will control several amperes in the aerial wire.

AMPLIFIERS, MULTI-STAGE.--A receiving set using two or more amplifiers. Also called _cascade amplification_.

AMPLIFIER, VACUUM TUBE.--A vacuum tube that is used either to amplify the radio frequency currents or the audio frequency currents.

AMPLITUDE OF WAVE.--The greatest distance that a point moves from its position of rest.

AMPLIFYING TRANSFORMER, AUDIO.--See _Transformer, Audio Amplifying_.

AMPLIFYING MODULATOR VACUUM TUBE.--See _Vacuum Tube, Amplifying Modulator_.

AMPLIFYING TRANSFORMER RADIO.--See _Transformer, Radio Amplifying_.

ANTENNA, AMATEUR.--See _Aerial, Amateur_.

ANTENNA SWITCH.--See _Switch, Aerial_.

APPARATUS SYMBOLS.--See _Symbols, Apparatus_.

ARMSTRONG CIRCUIT.--See _Circuit, Armstrong_.

ATMOSPHERICS.--Same as _Static_, which see.

ATTENUATION.--In Sending wireless telegraph and telephone messages the amplitude of the electric waves is damped out as the distance increases. This is called _attenuation_ and it increases as the frequency is increased. This is the reason why short wave lengths will not carry as far as long wave lengths.

AUDIO FREQUENCY AMPLIFIER.--See _Amplifier, Audio Frequency_.

AUDIO FREQUENCY AMPLIFICATION.--See _Amplification, Audio Frequency_.

AUDIBILITY METER.--See _Meter, Audibility_.

AUDIO FREQUENCY.--See _Frequency, Audio_.

AUDIO FREQUENCY CURRENT.--See _Current, Audio Frequency_.

AUDION.--An early trade name given to the vacuum tube detector.

AUTODYNE RECEPTOR.--See _Receptor, Autodyne_.

AUTO TRANSFORMER.--See _Transformer, Auto_.

BAKELITE.--A manufactured insulating compound.

B BATTERY.--See _Battery B_.

BAND, WAVE LENGTH.--See _Wave Length Band_.

BASKET WOUND COILS.--See _Coils, Inductance_.

BATTERY, A.--The 6-volt storage battery used to heat the filament of a vacuum tube, detector or amplifier.

BATTERY, B.--The 22-1/2-volt dry cell battery used to energize the plate of a vacuum tube detector or amplifier.

BATTERY, BOOSTER.--This is the battery that is connected in series with the crystal detector.

BATTERY, C.--A small dry cell battery sometimes used to give the grid of a vacuum tube detector a bias potential.

BATTERY, EDISON STORAGE.--A storage battery in which the elements are made of nickel and iron and immersed in an alkaline _electrolyte_.

BATTERY, LEAD STORAGE.--A storage battery in which the elements are made of lead and immersed in an acid electrolyte.

BATTERY POLES.--See _Poles, Battery_.

BATTERY, PRIMARY.--A battery that generates current by chemical action.

BATTERY, STORAGE.--A battery that develops a current after it has been charged.

BEAT RECEPTION.--See _Heterodyne Reception_.

BED SPRINGS AERIAL.--See _Aerial, Bed Springs_.

BLUB BLUB.--Over modulation in wireless telephony.

BROAD WAVE.--See _Wave, Broad_.

BRUSH DISCHARGE.--See _Discharge_.

BUZZER MODULATION.--See _Modulation, Buzzer_.

BLUE GLOW DISCHARGE.--See _Discharge_.

BOOSTER BATTERY.--See _Battery, Booster_.

BROADCASTING.--Sending out intelligence and music from a central station for the benefit of all who live within range of it and who have receiving sets.

CAPACITANCE.--Also called by the older name of _capacity_. The capacity of a condenser, inductance coil or other device capable of retaining a charge of electricity. Capacitance is measured in terms of the _microfarad_.

CAPACITIVE COUPLING.--See _Coupling, Capacitive_.

CAPACITY.--Any object that will retain a charge of electricity; hence an aerial wire, a condenser or a metal plate is sometimes called a _capacity_.

CAPACITY, AERIAL.--The amount to which an aerial wire system can be charged. The _capacitance_ of a small amateur aerial is from 0.0002 to 0.0005 microfarad.

CAPACITY, DISTRIBUTED.--A coil of wire not only has inductance, but also a certain small capacitance. Coils wound with their turns parallel and having a number of layers have a _bunched capacitance_ which produces untoward effects in oscillation circuits. In honeycomb and other stagger wound coils the capacitance is more evenly distributed.

CAPACITY REACTANCE.--See _Reactance, Capacity_.

CAPACITY UNIT.--See _Farad_.

CARBON RHEOSTATS.--See _Rheostat, Carbon_.

CARBORUNDUM DETECTOR.--See _Detector_.

CARRIER CURRENT TELEPHONY.--See _Wired-Wireless_.

CARRIER FREQUENCY.--See _Frequency, Carrier_.

CARRIER FREQUENCY TELEPHONY.--See _Wired-Wireless_.

CASCADE AMPLIFICATION.--Two or more amplifying tubes hooked up in a receiving set.

CAT WHISKER CONTACT.--A long, thin wire which makes contact with the crystal of a detector.

CENTIMETER OF CAPACITANCE.--Equal to 1.11 _microfarads_.

CENTIMETER OF INDUCTANCE.--Equal to one one-thousandth part of a _microhenry_.

CELLULAR COILS.--See _Coils, Inductance_.

C.G.S. ELECTROSTATIC UNIT OF CAPACITANCE.--See _Centimeter of Capacitance_.

CHARACTERISTICS.--The special behavior of a device, such as an aerial, a detector tube, etc.

CHARACTERISTICS, GRID.--See _Grid Characteristics_.

CHOKE COILS.--Coils that prevent the high voltage oscillations from surging back into the transformer and breaking down the insulation.

CHOPPER MODULATION.--See _Modulation, Chopper_.

CIRCUIT.--Any electrical conductor through which a current can flow. A low voltage current requires a loop of wire or other conductor both ends of which are connected to the source of current before it can flow. A high frequency current will surge in a wire which is open at both ends like the aerial.

Closed Circuit.--A circuit that is continuous.

Open Circuit.--A conductor that is not continuous.

Coupled Circuits.--Open and closed circuits connected together by inductance coils, condensers or resistances. See _coupling_.

Close Coupled Circuits.--Open and closed circuits connected directly together with a single inductance coil.

Loose Coupled Circuits.--Opened and closed currents connected together inductively by means of a transformer.

Stand-by Circuits.--Also called _pick-up_ circuits. When listening-in for possible calls from a number of stations, a receiver is used which will respond to a wide band of wave lengths.

Armstrong Circuits.--The regenerative circuit invented by Major E. H. Armstrong.

CLOSE COUPLED CIRCUITS.--See _Currents, Close Coupled_.

CLOSED CIRCUIT.--See _Circuit, Closed_.

CLOSED CORE TRANSFORMER.--See _Transformer, Closed Core_.

CODE.--

Continental.--Same as _International_.

International.--On the continent of Europe land lines use the _Continental Morse_ alphabetic code. This code has come to be used throughout the world for wireless telegraphy and hence it is now called the _International code_. It is given on Page 305. [Appendix: International Morse Code].

Morse.--The code devised by Samuel F. B. Morse and which is used on the land lines in the U. S.

National Electric.--A set of rules and requirements devised by the _National Board of Fire Underwriters_ for the electrical installations in buildings on which insurance companies carry risks. This code also covers the requirements for wireless installations. A copy may be had from the _National Board of Fire Underwriters_, New York City, or from your insurance agent.

National Electric Safety.--The Bureau of Standards, Washington, D. C., have investigated the precautions which should be taken for the safe operation of all electric equipment. A copy of the _Bureau of Standards Handbook No. 3_ can be had for 40 cents from the _Superintendent of Documents_.

COEFFICIENT OF COUPLING.--See _Coupling, Coefficient of_.

COIL AERIAL.--See _Aerial, Loop_.

COIL ANTENNA.--See _Aerial, Loop_.

COIL, INDUCTION.--An apparatus for changing low voltage direct currents into high voltage, low frequency alternating currents. When fitted with a spark gap the high voltage, low frequency currents are converted into high voltage, high frequency currents. It is then also called a _spark coil_ and a _Ruhmkorff coil_.

COIL, LOADING.--A coil connected in the aerial or closed oscillation circuit so that longer wave lengths can be received.

COIL, REPEATING.--See _Repeating Coil_.

COIL, ROTATING.--One which rotates on a shaft instead of sliding as in a _loose coupler_. The rotor of a _variometer_ or _variocoupler_ is a _rotating coil_.

COILS, INDUCTANCE.--These are the tuning coils used for sending and receiving sets. For sending sets they are formed of one and two coils, a single sending coil is generally called a _tuning inductance coil_, while a two-coil tuner is called an _oscillation transformer_. Receiving tuning coils are made with a single layer, single coil, or a pair of coils, when it is called an oscillation _transformer_. Some tuning inductance coils have more than one layer, they are then called _lattice wound_, _cellular_, _basket wound_, _honeycomb_, _duo-lateral_, _stagger wound_, _spider-web_ and _slab_ coils.

COMMERCIAL FREQUENCY.--See _Frequency, Commercial_.

CONDENSER, AERIAL SERIES.--A condenser placed in the aerial wire system to cut down the wave length.

CONDENSER, VERNIER.--A small variable condenser used for receiving continuous waves where very sharp tuning is desired.

CONDENSER.--All conducting objects with their insulation form capacities, but a _condenser_ is understood to mean two sheets or plates of metal placed closely together but separated by some insulating material.

Adjustable Condenser.--Where two or more condensers can be coupled together by means of plugs, switches or other devices.

Aerial Condenser.--A condenser connected in the aerial.

Air Condenser.--Where air only separates the sheets of metal.

By-Pass Condenser.--A condenser connected in the transmitting currents so that the high frequency currents cannot flow back through the power circuit.

Filter Condenser.--A condenser of large capacitance used in combination with a filter reactor for smoothing out the pulsating direct currents as they come from the rectifier.

Fixed Condenser.--Where the plates are fixed relatively to one another.

Grid Condenser.--A condenser connected in series with the grid lead.

Leyden Jar Condenser.--Where glass jars are used.

Mica Condenser.--Where mica is used.

Oil Condenser.--Where the plates are immersed in oil.

Paper Condenser.--Where paper is used as the insulating material.

Protective.--A condenser of large capacity connected across the low voltage supply circuit of a transmitter to form a by-path of kick-back oscillations.

Variable Condenser.--Where alternate plates can be moved and so made to interleave more or less with a set of fixed plates.

Vernier.--A small condenser with a vernier on it so that it can be very accurately varied. It is connected in parallel with the variable condenser used in the primary circuit and is used for the reception of continuous waves where sharp tuning is essential.

CONDENSITE.--A manufactured insulating compound.

CONDUCTIVITY.--The conductance of a given length of wire of uniform cross section. The reciprocal of _resistivity_.

CONTACT DETECTORS.--See _Detectors, Contact_.

CONTINENTAL CODE.--See _Code, Continental_.

COULOMB.--The quantity of electricity transferred by a current of 1 ampere in 1 second.

CONVECTIVE DISCHARGE.--See _Discharge_.

CONVENTIONAL SIGNALS.--See _Signals, Conventional_.

COUNTER ELECTROMOTIVE FORCE.--See _Electromotive Force, Counter_.

COUNTERPOISE. A duplicate of the aerial wire that is raised a few feet above the earth and insulated from it. Usually no connection is made with the earth itself.

COUPLED CIRCUITS.--See _Circuit, Coupled_.

COUPLING.--When two oscillation circuits are connected together either by the magnetic field of an inductance coil, or by the electrostatic field of a condenser.

COUPLING, CAPACITIVE.--Oscillation circuits when connected together by condensers instead of inductance coils.

COUPLING, COEFFICIENT OF.--The measure of the closeness of the coupling between two coils.

COUPLING, INDUCTIVE.--Oscillation circuits when connected together by inductance coils.

COUPLING, RESISTANCE.--Oscillation circuits connected together by a resistance.

CRYSTAL RECTIFIER.--A crystal detector.

CURRENT, ALTERNATING (A.C.).--A low frequency current that surges to and fro in a circuit.

CURRENT, AUDIO FREQUENCY.--A current whose frequency is low enough to be heard in a telephone receiver. Such a current usually has a frequency of between 200 and 2,000 cycles per second.

CURRENT, PLATE.--The current which flows between the filament and the plate of a vacuum tube.

CURRENT, PULSATING.--A direct current whose voltage varies from moment to moment.

CURRENT, RADIO FREQUENCY.--A current whose frequency is so high it cannot be heard in a telephone receiver. Such a current may have a frequency of from 20,000 to 10,000,000 per second.

CURRENTS, HIGH FREQUENCY.--(1) Currents that oscillate from 10,000 to 300,000,000 times per second. (2) Electric oscillations.

CURRENTS, HIGH POTENTIAL.--(1) Currents that have a potential of more than 10,000 volts. (2) High voltage currents.

CYCLE.--(1) A series of changes which when completed are again at the starting point. (2) A period of time at the end of which an alternating or oscillating current repeats its original direction of flow.

DAMPING.--The degree to which the energy of an electric oscillation is reduced. In an open circuit the energy of an oscillation set up by a spark gap is damped out in a few swings, while in a closed circuit it is greatly prolonged, the current oscillating 20 times or more before the energy is dissipated by the sum of the resistances of the circuit.

DECREMENT.--The act or process of gradually becoming less.

DETECTOR.--Any device that will (1) change the oscillations set up by the incoming waves into direct current, that is which will rectify them, or (2) that will act as a relay.

Carborundum.--One that uses a _carborundum_ crystal for the sensitive element. Carborundum is a crystalline silicon carbide formed in the electric furnace.

Cat Whisker Contact.--See _Cat Whisker Contact_.

Chalcopyrite.--Copper pyrites. A brass colored mineral used as a crystal for detectors. See _Zincite_.

Contact.--A crystal detector. Any kind of a detector in which two dissimilar but suitable solids make contact.

Ferron.--A detector in which iron pyrites are used as the sensitive element.

Galena.--A detector that uses a galena crystal for the rectifying element.

Iron Pyrites.--A detector that uses a crystal of iron pyrites for its sensitive element.

Molybdenite.--A detector that uses a crystal of _sulphide of molybdenum_ for the sensitive element.

Perikon.--A detector in which a _bornite_ crystal makes contact with a _zincite_ crystal.

Silicon.--A detector that uses a crystal of silicon for its sensitive element.

Vacuum Tube.--A vacuum tube (which see) used as a detector.

Zincite.--A detector in which a crystal of _zincite_ is used as the sensitive element.

DE TUNING.--A method of signaling by sustained oscillations in which the key when pressed down cuts out either some of the inductance or some of the capacity and hence greatly changes the wave length.

DIELECTRIC.--An insulating material between two electrically charged plates in which there is set up an _electric strain_, or displacement.

DIELECTRIC STRAIN.--The electric displacement in a dielectric.

DIRECTIONAL AERIAL.--See _Aerial, Directional_.

DIRECTION FINDER.--See _Aerial, Loop_.

DISCHARGE.--(1) A faintly luminous discharge that takes place from the positive pointed terminal of an induction coil, or other high potential apparatus; is termed a _brush discharge_. (2) A continuous discharge between the terminals of a high potential apparatus is termed a _convective discharge_. (3) The sudden breaking-down of the air between the balls forming the spark gap is termed a _disruptive discharge_; also called an _electric spark_, or just _spark_ for short. (4) When a tube has a poor vacuum, or too large a battery voltage, it glows with a blue light and this is called a _blue glow discharge_.

DISRUPTIVE DISCHARGE.--See _Discharge_.

DISTRESS CALL. [Morse code:] ...---... (SOS).

DISTRIBUTED CAPACITY.--See _Capacity, Distributed_.

DOUBLE HUMP RESONANCE CURVE.--A resonance curve that has two peaks or humps which show that the oscillating currents which are set up when the primary and secondary of a tuning coil are closely coupled have two frequencies.

DUO-LATERAL COILS.--See _Coils, Inductance_.

DUPLEX COMMUNICATION.--A wireless telephone system with which it is possible to talk between both stations in either direction without the use of switches. This is known as the _duplex system_.

EARTH CAPACITY.--An aerial counterpoise.

EARTH CONNECTION.--Metal plates or wires buried in the ground or immersed in water. Any kind of means by which the sending and receiving apparatus can be connected with the earth.

EDISON STORAGE BATTERY.--See _Storage Battery, Edison_.

ELECTRIC ENERGY.--The power of an electric current.

ELECTRIC OSCILLATIONS.--See _Oscillations, Electric_.

ELECTRIC SPARK.--See _Discharge, Spark_.

ELECTRICITY, NEGATIVE.--The opposite of _positive electricity_. Negative electricity is formed of negative electrons which make up the outside particles of an atom.

ELECTRICITY, POSITIVE.--The opposite of _negative electricity_. Positive electricity is formed of positive electrons which make up the inside particles of an atom.

ELECTRODES.--Usually the parts of an apparatus which dip into a liquid and carry a current. The electrodes of a dry battery are the zinc and carbon elements. The electrodes of an Edison storage battery are the iron and nickel elements, and the electrodes of a lead storage battery are the lead elements.

ELECTROLYTES.--The acid or alkaline solutions used in batteries.

ELECTROMAGNETIC WAVES.--See _Waves, Electric_.

ELECTROMOTIVE FORCE.--Abbreviated _emf_. The force that drives an electric current along a conductor. Also loosely called _voltage_.

ELECTROMOTIVE FORCE, COUNTER.--The emf. that is set up in a direction opposite to that in which the current is flowing in a conductor.

ELECTRON.--(1) A negative particle of electricity that is detached from an atom. (2) A negative particle of electricity thrown off from the incandescent filament of a vacuum tube.

ELECTRON FLOW.--The passage of electrons between the incandescent filament and the cold positively charged plate of a vacuum tube.

ELECTRON RELAY.--See _Relay, Electron_.

ELECTRON TUBE.--A vacuum tube or a gas-content tube used for any purpose in wireless work. See _Vacuum Tube_.

ELECTROSE INSULATORS.--Insulators made of a composition material the trade name of which is _Electrose_.

ENERGY, ELECTRIC.--See _Electric Energy_.

ENERGY UNIT.--The _joule_, which see, Page 308 [Appendix: Definitions of Electric and Magnetic Units].

FADING.--The sudden variation in strength of signals received from a transmitting station when all the adjustments of both sending and receiving apparatus remain the same. Also called _swinging_.

FARAD.--The capacitance of a condenser in which a potential difference of 1 volt causes it to have a charge of 1 coulomb of electricity.

FEED-BACK ACTION.--Feeding back the oscillating currents in a vacuum tube to amplify its power. Also called _regenerative action_.

FERROMAGNETIC CONTROL.--See _Magnetic Amplifier_.

FILAMENT.--The wire in a vacuum tube that is heated to incandescence and which throws off electrons.

FILAMENT RHEOSTAT.--See _Rheostat, Filament_.

FILTER.--Inductance coils or condensers or both which (1) prevent troublesome voltages from acting on the different circuits, and (2) smooth out alternating currents after they have been rectified.

FILTER REACTOR.--See _Reactor, Filter_.

FIRE UNDERWRITERS.--See _Code, National Electric_.

FIXED GAP.--See _Gap_.

FLEMING VALVE.--A two-electrode vacuum tube.

FORCED OSCILLATIONS.--See _Oscillations, Forced_.

FREE OSCILLATIONS.--See _Oscillations, Free_.

FREQUENCY, AUDIO.--(1) An alternating current whose frequency is low enough to operate a telephone receiver and, hence, which can be heard by the ear. (2) Audio frequencies are usually around 500 or 1,000 cycles per second, but may be as low as 200 and as high as 10,000 cycles per second.

Carrier.--A radio frequency wave modulated by an audio frequency wave which results in setting of _three_ radio frequency waves. The principal radio frequency is called the carrier frequency, since it carries or transmits the audio frequency wave.

Commercial.--(1) Alternating current that is used for commercial purposes, namely, light, heat and power. (2) Commercial frequencies now in general use are from 25 to 50 cycles per second.

Natural.--The pendulum and vibrating spring have a _natural frequency_ which depends on the size, material of which it is made, and the friction which it has to overcome. Likewise an oscillation circuit has a natural frequency which depends upon its _inductance_, _capacitance_ and _resistance_.

Radio.--(1) An oscillating current whose frequency is too high to affect a telephone receiver and, hence, cannot be heard by the ear. (2) Radio frequencies are usually between 20,000 and 2,000,000 cycles per second but may be as low as 10,000 and as high as 300,000,000 cycles per second.

Spark.--The number of sparks per second produced by the discharge of a condenser.

GAP, FIXED.--One with fixed electrodes.

GAP, NON-SYNCHRONOUS.--A rotary spark gap run by a separate motor which may be widely different from that of the speed of the alternator.

GAP, QUENCHED.--(1) A spark gap for the impulse production of oscillating currents. (2) This method can be likened to one where a spring is struck a single sharp blow and then continues to set up vibrations.

GAP, ROTARY.--One having fixed and rotating electrodes.

GAP, SYNCHRONOUS.--A rotary spark gap run at the same speed as the alternator which supplies the power transformer. Such a gap usually has as many teeth as there are poles on the generator. Hence one spark occurs per half cycle.

GAS-CONTENT TUBE.--See _Vacuum Tube._

GENERATOR TUBE.--A vacuum tube used to set up oscillations. As a matter of fact it does not _generate_ oscillations, but changes the initial low voltage current that flows through it into oscillations. Also called an _oscillator tube_ and a _power tube._

GRID BATTERY.--See _Battery C._

GRID CHARACTERISTICS.--The various relations that could exist between the voltages and currents of the grid of a vacuum tube, and the values which do exist between them when the tube is in operation. These characteristics are generally shown by curves.

GRID CONDENSER.--See _Condenser, Grid._

GRID LEAK.--A high resistance unit connected in the grid lead of both sending and receiving sets. In a sending set it keeps the voltage of the grid at a constant value and so controls the output of the aerial. In a receiving set it controls the current flowing between the plate and filament.

GRID MODULATION.--See _Modulation, Grid._

GRID POTENTIAL.--The negative or positive voltage of the grid of a vacuum tube.

GRID VOLTAGE.--See _Grid Potential._

GRINDERS.--The most common form of _Static,_ which see. They make a grinding noise in the headphones.

GROUND.--See _Earth Connection._

GROUND, AMATEUR.--A water-pipe ground.

GROUND, WATERPIPE.--A common method of grounding by amateurs is to use the waterpipe, gaspipe or radiator.

GUIDED WAVE TELEPHONY.--See _Wired Wireless._

HARD TUBE.--A vacuum tube in which the vacuum is _high,_ that is, exhausted to a high degree.

HELIX.--(1) Any coil of wire. (2) Specifically a transmitter tuning inductance coil.

HENRY.--The inductance in a circuit in which the electromotive force induced is 1 volt when the inducing current varies at the rate of 1 ampere per second.

HETERODYNE RECEPTION.--(1) Receiving by the _beat_ method. (2) Receiving by means of superposing oscillations generated at the receiving station on the oscillations set up in the aerial by the incoming waves.

HETERODYNE RECEPTOR.--See _Receptor, Heterodyne._

HIGH FREQUENCY CURRENTS.--See _Currents, High Frequency._

HIGH FREQUENCY RESISTANCE.--See _Resistance, High Frequency._

HIGH POTENTIAL CURRENTS.--See _Currents, High Potential._

HIGH VOLTAGE CURRENTS.--See _Currents, High Potential._

HONEYCOMB COILS.--See _Coils, Inductance._

HORSE-POWER.--Used in rating steam machinery. It is equal to 746 watts.

HOT WIRE AMMETER.--See _Ammeter, Hot Wire._

HOWLING.--Where more than three stages of radio amplification, or more than two stages of audio amplification, are used howling noises are apt to occur in the telephone receivers.

IMPEDANCE.--An oscillation circuit has _reactance_ and also _resistance,_ and when these are combined the total opposition to the current is called _impedance._

INDUCTANCE COILS.--See _Coils, Inductance._

INDUCTANCE COIL, LOADING.--See _Coil, Loading Inductance._

INDUCTIVE COUPLING.--See _Coupling, Inductive._

INDUCTIVE REACTANCE.--See _Reactance, Inductive._

INDUCTION COIL.--See _Coil, Induction._

INDUCTION, MUTUAL.--Induction produced between two circuits or coils close to each other by the mutual interaction of their magnetic fields.

INSULATION.--Materials used on and around wires and other conductors to keep the current from leaking away.

INSPECTOR, RADIO.--A U. S. inspector whose business it is to issue both station and operators' licenses in the district of which he is in charge.

INTERFERENCE.--The crossing or superposing of two sets of electric waves of the same or slightly different lengths which tend to oppose each other. It is the untoward interference between electric waves from different stations that makes selective signaling so difficult a problem.

INTERMEDIATE WAVES.--See _Waves._

IONIC TUBES.--See _Vacuum Tubes._

INTERNATIONAL CODE.--See Code, International.

JAMMING.--Waves that are of such length and strength that when they interfere with incoming waves they drown them out.

JOULE.--The energy spent in 1 second by a flow of 1 ampere in 1 ohm.

JOULE'S LAW.--The relation between the heat produced in seconds to the resistance of the circuit, to the current flowing in it.

KENOTRON.--The trade name of a vacuum tube rectifier made by the _Radio Corporation of America._

KICK-BACK.--Oscillating currents that rise in voltage and tend to flow back through the circuit that is supplying the transmitter with low voltage current.

KICK-BACK PREVENTION.--See _Prevention, Kick-Back._

KILOWATT.--1,000 watts.

LAMBDA.--See Pages 301, 302. [Appendix: Useful Abbreviations].

LATTICE WOUND COILS.--See _Coils, Inductance._

LIGHTNING SWITCH.--See _Switch, Lightning._

LINE RADIO COMMUNICATION.--See _Wired Wireless._

LINE RADIO TELEPHONY.--See _Telephony, Line Radio._

LITZENDRAHT.--A conductor formed of a number of fine copper wires either twisted or braided together. It is used to reduce the _skin effect._ See _Resistance, High Frequency._

LOAD FLICKER.--The flickering of electric lights on lines that supply wireless transmitting sets due to variations of the voltage on opening and closing the key.

LOADING COIL.--See _Coil, Loading._

LONG WAVES.--See _Waves._

LOOP AERIAL.--See _Aerial, Loop._

LOOSE COUPLED CIRCUITS.--See _Circuits, Loose Coupled._

LOUD SPEAKER.--A telephone receiver connected to a horn, or a specially made one, that reproduces the incoming signals, words or music loud enough to be heard by a room or an auditorium full of people, or by large crowds out-doors.

MAGNETIC POLES.--See _Poles, Magnetic._

MEGOHM.--One million ohms.

METER, AUDIBILITY.--An instrument for measuring the loudness of a signal by comparison with another signal. It consists of a pair of headphones and a variable resistance which have been calibrated.

MHO.--The unit of conductance. As conductance is the reciprocal of resistance it is measured by the _reciprocal ohm_ or _mho._

MICA.--A transparent mineral having a high insulating value and which can be split into very thin sheets. It is largely used in making condensers both for transmitting and receiving sets.

MICROFARAD.--The millionth part of a _farad._

MICROHENRY.--The millionth part of a _farad._

MICROMICROFARAD.--The millionth part of a _microfarad._

MICROHM.--The millionth part of an _ohm._

MICROPHONE TRANSFORMER.--See _Transformer, Microphone._

MICROPHONE TRANSMITTER.--See _Transmitter, Microphone._

MILLI-AMMETER.--An ammeter that measures a current by the one-thousandth of an ampere.

MODULATION.--(1) Inflection or varying the voice. (2) Varying the amplitude of oscillations by means of the voice.

MODULATION, BUZZER.--The modulation of radio frequency oscillations by a buzzer which breaks up the sustained oscillations of a transmitter into audio frequency impulses.

MILLIHENRY.--The thousandth part of a _henry._

MODULATION, CHOPPER.--The modulation of radio frequency oscillations by a chopper which breaks up the sustained oscillations of a transmitter into audio frequency impulses.

MODULATION, GRID.--The scheme of modulating an oscillator tube by connecting the secondary of a transformer, the primary of which is connected with a battery and a microphone transmitter, in the grid lead.

MODULATION, OVER.--See _Blub Blub._

MODULATION, PLATE.--Modulating the oscillations set up by a vacuum tube by varying the current impressed on the plate.

MODULATOR TUBE.--A vacuum tube used as a modulator.

MOTION, WAVE.--(1) The to and fro motion of water at sea. (2) Waves transmitted by, in and through the air, or sound waves. (3) Waves transmitted by, in and through the _ether,_ or _electromagnetic waves,_ or _electric waves_ for short.

MOTOR-GENERATOR.--A motor and a dynamo built to run at the same speed and mounted on a common base, the shafts being coupled together. In wireless it is used for changing commercial direct current into direct current of higher voltages for energizing the plate of a vacuum tube oscillator.

MULTI-STAGE AMPLIFIERS.--See _Amplifiers, Multi-Stage._

MUTUAL INDUCTION.--See _Induction, Mutual._

MUSH.--Irregular intermediate frequencies set up by arc transmitters which interfere with the fundamental wave lengths.

MUSHY NOTE.--A note that is not clear cut, and hence hard to read, which is received by the _heterodyne method_ when damped waves or modulated continuous waves are being received.

NATIONAL ELECTRIC CODE.--See _Code, National Electric._

NATIONAL ELECTRIC SAFETY CODE.--See _Code, National Electric Safety._

NEGATIVE ELECTRICITY.--See _Electricity, Negative._

NON-SYNCHRONOUS GAP.--See _Gap, Non-Synchronous._

OHM.--The resistance of a thread of mercury at the temperature of melting ice, 14.4521 grams in mass, of uniform cross-section and a length of 106.300 centimeters.

OHM'S LAW.--The important fixed relation between the electric current, its electromotive force and the resistance of the conductor in which it flows.

OPEN CIRCUIT.--See _Circuit, Open._

OPEN CORE TRANSFORMER.--See _Transformer, Open Core._

OSCILLATION TRANSFORMER.--See _Transformer, Oscillation._

OSCILLATIONS, ELECTRIC.--A current of high frequency that surges through an open or a closed circuit. (1) Electric oscillations may be set up by a spark gap, electric arc or a vacuum tube, when they have not only a high frequency but a high potential, or voltage. (2) When electric waves impinge on an aerial wire they are transformed into electric oscillations of a frequency equal to those which emitted the waves, but since a very small amount of energy is received their potential or voltage is likewise very small.

Sustained.--Oscillations in which the damping factor is small.

Damped.--Oscillations in which the damping factor is large.

Free.--When a condenser discharges through an oscillation circuit, where there is no outside electromotive force acting on it, the oscillations are said to be _free._

Forced.--Oscillations that are made to surge in a circuit whose natural period is different from that of the oscillations set up in it.

OSCILLATION TRANSFORMER.--See _Transformer._

OSCILLATION VALVE.--See _Vacuum Tube._

OSCILLATOR TUBE.--A vacuum tube which is used to produce electric oscillations.

OVER MODULATION.--See _Blub Blub._

PANCAKE OSCILLATION TRANSFORMER.--Disk-shaped coils that are used for receiving tuning inductances.

PERMEABILITY, MAGNETIC.--The degree to which a substance can be magnetized. Iron has a greater magnetic permeability than air.

PHASE.--A characteristic aspect or appearance that takes place at the same point or part of a cycle.

PICK-UP CIRCUITS.--See _Circuits, Stand-by._

PLATE CIRCUIT REACTOR.--See _Reactor, Plate Circuit._

PLATE CURRENT.--See _Current, Plate._

PLATE MODULATION.--See _Modulation, Plate._

PLATE VOLTAGE.--See _Foliage, Plate._

POLES, BATTERY.--The positive and negative terminals of the elements of a battery. On a storage battery these poles are marked + and - respectively.

POLES, MAGNETIC.--The ends of a magnet.

POSITIVE ELECTRICITY.--See _Electricity, Positive._

POTENTIAL DIFFERENCE.--The electric pressure between two charged conductors or surfaces.

POTENTIOMETER.--A variable resistance used for subdividing the voltage of a current. A _voltage divider._

POWER TRANSFORMER.--See _Transformer, Power._

POWER TUBE.--See _Generator Tube._

PRIMARY BATTERY.--See _Battery, Primary._

PREVENTION, KICK-BACK.--A choke coil placed in the power circuit to prevent the high frequency currents from getting into the transformer and breaking down the insulation.

Q S T.--An abbreviation used in wireless communication for (1) the question "Have you received the general call?" and (2) the notice, "General call to all stations."

QUENCHED GAP.--See _Gap, Quenched._

RADIATION.--The emission, or throwing off, of electric waves by an aerial wire system.

RADIO AMMETER.--See _Ammeter, Hot Wire._

RADIO FREQUENCY.--See _Frequency, Radio._

RADIO FREQUENCY AMPLIFICATION.--See _Amplification, Radio Frequency._

RADIO FREQUENCY CURRENT.--See _Current, Radio Frequency._

RADIO INSPECTOR.--See _Inspector, Radio_.

RADIOTRON.--The trade name of vacuum tube detectors, amplifiers, oscillators and modulators made by the _Radio Corporation of America_.

RADIO WAVES.--See _Waves, Radio_.

REACTANCE.--When a circuit has inductance and the current changes in value, it is opposed by the voltage induced by the variation of the current.

REACTANCE, CAPACITY.--The capacity reactance is the opposition offered to a current by a capacity. It is measured as a resistance, that is, in _ohms_.

RECEIVING TUNING COILS.--See _Coils, Inductance_.

RECEIVER, LOUD SPEAKING.--See _Loud Speakers_.

RECEIVER, WATCH CASE.--A compact telephone receiver used for wireless reception.

REACTANCE, INDUCTIVE.--The inductive reactance is the opposition offered to the current by an inductance coil. It is measured as a resistance, that is, in _ohms_.

REACTOR, FILTER.--A reactance coil for smoothing out the pulsating direct currents as they come from the rectifier.

REACTOR, PLATE CIRCUIT.--A reactance coil used in the plate circuit of a wireless telephone to keep the direct current supply at a constant voltage.

RECEIVER.--(1) A telephone receiver. (2) An apparatus for receiving signals, speech or music. (3) Better called a _receptor_ to distinguish it from a telephone receiver.

RECTIFIER.--(1) An apparatus for changing alternating current into pulsating direct current. (2) Specifically in wireless (_a_) a crystal or vacuum tube detector, and (_b_) a two-electrode vacuum tube used for changing commercial alternating current into direct current for wireless telephony.

REGENERATIVE AMPLIFICATION.--See _Amplification, Regenerative_.

RECEPTOR.--A receiving set.

RECEPTOR, AUTODYNE.--A receptor that has a regenerative circuit and the same tube is used as a detector and as a generator of local oscillations.

RECEPTOR, BEAT.--A heterodyne receptor.

RECEPTOR, HETERODYNE.--A receiving set that uses a separate vacuum tube to set up the second series of waves for beat reception.

REGENERATIVE ACTION.--See _Feed-Back Action._

REGENERATIVE AMPLIFICATION.--See _Amplification, Regenerative._

RELAY, ELECTRON.--A vacuum tube when used as a detector or an amplifier.

REPEATING COIL.--A transformer used in connecting up a wireless receiver with a wire transmitter.

RESISTANCE.--The opposition offered by a wire or other conductor to the passage of a current.