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 ma.s.s, 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._