AMPLIFIER, AUDIO FREQUENCY.--A vacuum tube or other device that amplifies the signals after pa.s.sing 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_.