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.

RESISTANCE, AERIAL.--The resistance of the aerial wire to oscillating currents. This is greater than its ordinary ohmic resistance due to the skin effect. See Resistance, High Frequency.

RESISTANCE BOX.--See Resistor.

RESISTANCE COUPLING.--See Coupling, Resistance.

RESISTANCE, HIGH FREQUENCY.--When a high frequency current oscillates on a wire two things take place that are different than when a direct or alternating current flows through it, and these are (1) the current inside of the wire lags behind that of the current on the surface, and (2) the amplitude of the current is largest on the surface and grows smaller as the center of the wire is reached. This uneven distribution of the current is known as the skin effect and it amounts to the same thing as reducing the size of the wire, hence the resistance is increased.

RESISTIVITY.--The resistance of a given length of wire of uniform cross section. The reciprocal of conductivity.

RESISTOR.--A fixed or variable resistance unit or a group of such units. Variable resistors are also called resistance boxes and more often rheostats.

RESONANCE.--(1) Simple resonance of sound is its increase set up by one body by the sympathetic vibration of a second body. (2) By extension the increase in the amplitude of electric oscillations when the circuit in which they surge has a natural period that is the same, or nearly the same, as the period of the first oscillation circuit.

RHEOSTAT.--A variable resistance unit. See Resistor.

RHEOSTAT, CARBON.--A carbon rod, or carbon plates or blocks, when used as variable resistances.

RHEOSTAT, FILAMENT.--A variable resistance used for keeping the current of the storage battery which heats the filament of a vacuum tube at a constant voltage.

ROTATING COIL.--See Coil.

ROTARY GAP.--See Gap.

ROTOR.--The rotating coil of a variometer or a variocoupler.

RUHMKORFF COIL.--See Coil, Induction.

SATURATION.--The maximum plate current that a vacuum tube will take.

SENSITIVE SPOTS.--Spots on detector crystals that are sensitive to the action of electric oscillations.

SHORT WAVES.--See Waves.

SIDE WAVES.--See Wave Length Band.

SIGNALS, CONVENTIONAL.--(1) The International Morse alphabet and numeral code, punctuation marks, and a few important abbreviations used in wireless telegraphy. (2) Dot and dash signals for distress call, invitation to transmit, etc. Now used for all general public service wireless communication.

SKIN EFFECT.--See Resistance, High Frequency.

SOFT TUBE.--A vacuum tube in which the vacuum is low, that is, it is not highly exhausted.

SPACE CHARGE EFFECT.--The electric field intensity due to the pressure of the negative electrons in the space between the filament and plate which at last equals and neutralizes that due to the positive potential of the plate so that there is no force acting on the electrons near the filament.

SPARK.--See Discharge.

SPARK COIL.--See Coil, Induction.

SPARK DISCHARGE.--See Spark, Electric.

SPARK FREQUENCY.--See Frequency, Spark.

SPARK GAP.--(1) A spark gap, without the hyphen, means the apparatus in which sparks take place; it is also called a spark discharger. (2) Spark-gap, with the hyphen, means the air-gap between the opposed faces of the electrodes in which sparks are produced.

• Plain.--A spark gap with fixed electrodes.
• Rotary.--A spark gap with a pair of fixed electrodes and a number of electrodes mounted on a rotating element.
• Quenched.--A spark gap formed of a number of metal plates placed closely together and insulated from each other.

SPIDER WEB INDUCTANCE COIL.--See Coil, Spider Web Inductance.

SPREADER.--A stick of wood, or spar, that holds the wires of the aerial apart.

STAGGER WOUND COILS.--See Coils, Inductance.

STAND-BY CIRCUITS.--See Circuits, Stand-By.

STATIC.--Also called atmospherics, grinders, strays, X's, and, when bad enough, by other names. It is an electrical disturbance in the atmosphere which makes noises in the telephone receiver.

STATOR.--The fixed or stationary coil of a variometer or a variocoupler.

STORAGE BATTERY.--See Battery, Storage.

STRAY ELIMINATION.--A method for increasing the strength of the signals as against the strength of the strays. See Static.

STRAYS.--See Static.

STRANDED WIRE.--See Wire, Stranded.

SUPER-HETERODYNE RECEPTOR.--See Heterodyne, Super.

SWINGING.--See Fading.

SWITCH, AERIAL.--A switch used to change over from the sending to the receiving set, and the other way about, and connect them with the aerial.

SWITCH, LIGHTNING.--The switch that connects the aerial with the outside ground when the apparatus is not in use.

SYMBOLS, APPARATUS.--Also called conventional symbols. These are diagrammatic lines representing various parts of apparatus so that when a wiring diagram of a transmitter or a receptor is to be made it is only necessary to connect them together. They are easy to make and easy to read. See Page 307 [Appendix: Symbols Used for Apparatus].

SYNCHRONOUS GAP.--See Gap, Synchronous.

TELEPHONY, LINE RADIO.--See Wired Wireless.

THERMAL AMMETER.--See Ammeter, Hot Wire.

THREE ELECTRODE VACUUM TUBE.--See Vacuum Tube, Three Electrode.

TIKKER.--A slipping contact device that breaks up the sustained oscillations at the receiving end into groups so that the signals can be heard in the head phones. The device usually consists of a fine steel or gold wire slipping in the smooth groove of a rotating brass wheel.

TRANSFORMER.--A primary and a secondary coil for stepping up or down a primary alternating or oscillating current.

• A. C.--See Power Transformer.
• Air Cooled.--A transformer in which the coils are exposed to the air.
• Air Core.--With high frequency currents it is the general practice not to use iron cores as these tend to choke off the oscillations. Hence the core consists of the air inside of the coils.
• Auto.--A single coil of wire in which one part forms the primary and the other part the secondary by bringing out an intermediate tap.
• Audio Amplifying.--This is a transformer with an iron core and is used for frequencies up to say 3,000.
• Closed Core.--A transformer in which the path of the magnetic flux is entirely through iron. Power transformers have closed cores.
• Microphone.--A small transformer for modulating the oscillations set up by an arc or a vacuum tube oscillator.
• Oil Cooled.--A transformer in which the coils are immersed in oil.
• Open Core.--A transformer in which the path of the magnetic flux is partly through iron and partly through air. Induction coils have open cores.
• Oscillation.--A coil or coils for transforming or stepping down or up oscillating currents. Oscillation transformers usually have no iron cores when they are also called air core transformers.
• Power.--A transformer for stepping down a commercial alternating current for lighting and heating the filament and for stepping up the commercial a.c., for charging the plate of a vacuum tube oscillator.
• Radio Amplifying.--This is a transformer with an air core. It does not in itself amplify but is so called because it is used in connection with an amplifying tube.

TRANSMITTER, MICROPHONE.--A telephone transmitter of the kind that is used in the Bell telephone system.

TRANSMITTING TUNING COILS.--See Coils, Inductance.

TUNING.--When the open and closed oscillation circuits of a transmitter or a receptor are adjusted so that both of the former will permit electric oscillations to surge through them with the same frequency, they are said to be tuned. Likewise, when the sending and receiving stations are adjusted to the same wave length they are said to be tuned.

• Coarse Tuning.--The first adjustment in the tuning oscillation circuits of a receptor is made with the inductance coil and this tunes them coarse, or roughly.
• Fine Tuning.--After the oscillation circuits have been roughly tuned with the inductance coil the exact adjustment is obtained with the variable condenser and this is fine tuning.
• Sharp.--When a sending set will transmit or a receiving set will receive a wave of given length only it is said to be sharply tuned. The smaller the decrement the sharper the tuning.

TUNING COILS.--See Coils, Inductance.

TWO ELECTRODE VACUUM TUBE.--See Vacuum Tube, Two Electrode.

VACUUM TUBE.--A tube with two or three electrodes from which the air has been exhausted, or which is filled with an inert gas, and used as a detector, an amplifier, an oscillator or a modulator in wireless telegraphy and telephony.

• Amplifier.--See Amplifier, Vacuum Tube.
• Amplifying Modulator.--A vacuum tube used for modulating and amplifying the oscillations set up by the sending set.
• Gas Content.--A tube made like a vacuum tube and used as a detector but which contains an inert gas instead of being exhausted.
• Hard.--See Hard Tube.
• Rectifier.--(1) A vacuum tube detector. (2) a two-electrode vacuum tube used for changing commercial alternating current into direct current for wireless telephony.
• Soft.--See Soft Tube.
• Three Electrode.--A vacuum tube with three electrodes, namely a filament, a grid and a plate.
• Two Electrode.--A vacuum tube with two electrodes, namely the filament and the plate.

VALVE.--See Vacuum Tube.

VALVE, FLEMING.--See Fleming Valve.

VARIABLE CONDENSER.--See Condenser, Variable.

VARIABLE INDUCTANCE.--See Inductance, Variable.

VARIABLE RESISTANCE.--See Resistance, Variable.

VARIOCOUPLER.--A tuning device for varying the inductance of the receiving oscillation circuits. It consists of a fixed and a rotatable coil whose windings are not connected with each other.

VARIOMETER.--A tuning device for varying the inductance of the receiving oscillation currents. It consists of a fixed and a rotatable coil with the coils connected in series.

VERNIER CONDENSER.--See Condenser, Vernier.

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

VOLTAGE DIVIDER.--See Potentiometer.

VOLTAGE, PLATE.--The voltage of the current that is used to energize the plate of a vacuum tube.

VOLTMETER.--An instrument for measuring the voltage of an electric current.

WATCH CASE RECEIVER.--See Receiver, Watch Case.

WATER-PIPE GROUND.--See Ground, Water-Pipe.

WATT.--The power spent by a current of 1 ampere in a resistance of 1 ohm.

WAVE, BROAD.--A wave having a high decrement, when the strength of the signals is nearly the same over a wide range of wave lengths.

WAVE LENGTH.--Every wave of whatever kind has a length. The wave length is usually taken to mean the distance between the crests of two successive waves.

WAVE LENGTH BAND.--In wireless reception when continuous waves are being sent out and these are modulated by a microphone transmitter the different audio frequencies set up corresponding radio frequencies and the energy of these are emitted by the aerial; this results in waves of different lengths, or a band of waves as it is called.

WAVE METER.--An apparatus for measuring the lengths of electric waves set up in the oscillation circuits of sending and receiving sets.

WAVE MOTION.--Disturbances set up in the surrounding medium as water waves in and on the water, sound waves in the air and electric waves in the ether.

WAVES.--See Wave Motion.

WAVES, ELECTRIC.--Electromagnetic waves set up in and transmitted by and through the ether.

• Continuous. Abbreviated C.W.--Waves that are emitted without a break from the aerial. Also called undamped waves.
• Discontinuous.--Waves that are emitted periodically from the aerial. Also called damped waves. Damped.--See Discontinuous Waves.
• Intermediate.--Waves from 600 to 2,000 meters in length.
• Long.--Waves over 2,000 meters in length. Radio.--Electric waves used in wireless telegraphy and telephony.
• Short.--Waves up to 600 meters in length.
• Wireless.--Electric waves used in wireless telegraphy and telephony.
• Undamped.--See Continuous Waves.

WIRELESS TELEGRAPH CODE.--See Code, International.

WIRE, ENAMELLED.--Wire that is given a thin coat of enamel which insulates it.

WIRE, PHOSPHOR BRONZE.--A very strong wire made of an alloy of copper and containing a trace of phosphorus.

WIRED WIRELESS.--Continuous waves of high frequency that are sent over telephone wires instead of through space. Also called line radio communication; carrier frequency telephony, carrier current telephony; guided wave telephony and wired wireless.

X'S.--See Static.

ZINCITE.--See Detector.