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M

MACHINE KEYING

A method of cw keying using punched tape or other mechanical means to key a
transmitter [12].


MAGIC T

See BALANCED MIXER [18].

MAGIC-T JUNCTION

A combination of H-type and E-type T-junctions [11].

MAGNET WIRE

Wire coated with an enamel insulation and used in coils, relays, transformers, motor windings, and so forth [4].


MAGNETIC AMPLIFIER

An electromagnetic device that uses one or more saturable reactors to obtain
a large power gain. This device is used in servosystems requiring large amounts of power to move heavy loads [8] [15].


MAGNETIC FIELD

(1) The region in which the magnetic forces created by a permanent magnet or by a current-carrying conductor or coil can be detected [1] [2]. (2) The field that is produced when current flows through a conductor or antenna [10] [11].


MAGNETIC INDUCTION

Generating a voltage in a circuit by the creation of relative motion between a
magnetic field and the circuit. The relative motion can be the result of physical movement or the rise and fall of a magnetic field created by a changing current [5].


MAGNETIC LINES OF FORCE

Imaginary lines used for convenience to designate the direction in which magnetic forces are acting as a result of magnetomotive force [2].


MAGNETIC MICROPHONE

A microphone in which the sound waves vibrate a moving armature. The
armature consists of a coil wound on the armature and located between the pole pieces of a permanent magnet. The armature is mechanically linked to the diaphragm [12].


MAGNETIC POLES

The section of a magnet where the flux lines are concentrated; also where they
enter and leave the magnet [1].


MAGNETIC TRIP ELEMENT

A circuit breaker trip element that uses the increasing magnetic attraction of a coil with increased current to open the circuit [3].


MAGNETISM

The property possessed by certain materials by which these materials can exert
mechanical force on neighboring masses of magnetic materials and can cause currents to be induced in conducting bodies moving relative to the magnetized bodies [1].


MAGNETRON OSCILLATOR

An electron tube that provides a high power output. Theory of operation
is based on interaction of electrons with the crossed electric and magnetic fields in a resonant cavity [18].


MAINTENANCE

Work done to correct, reduce, or counteract wear, failure, and damage to equipment [16].


MAJOR LOBE

The lobe in which the greatest amount of radiation occurs [10].

MAJORITY CARRIERS

The mobile charge carriers (hole or electron) which are predominate in a
semiconductor material; for example, electrons in an N-type region [7].


MARCONI ANTENNA

A quarter-wave antenna that is operated with one end grounded and is positioned perpendicular to the earth [10].


MARK

An interval during which a signal is present. Also the presence of an RF signal in cw keying. The key-closed condition (presence of data) in communications systems [12].


MARKING

The state where a circuit is closed and current flows in teletypewriter operation [17].

MASK

A device used to deposit materials on a substrate in the desired pattern [14].

MASTER OSCILLATOR

In a transmitter, the oscillator that establishes the carrier frequency of the
output [18].


MASTER OSCILLATOR POWER AMPLIFIER

A transmitter in which the oscillator is isolated from the antenna by a power amplifier [12].


MATRIX

In computers, a logic network in the form of an array of input leads and output leads with logic elements connected at some of their intersections [13].


MATTER

Any physical entity that possesses mass [1].

MAXIMUM USABLE FREQUENCY

Maximum frequency that can be used for communications between two locations for a given time of day and a given angle of incidence [10].


MEASURE

(METROLOGY AUTOMATED SYSTEM FOR UNIFORM RECALL AND REPORTING)—The Navy data processing system designed to provide a standardized system for the recall, scheduling, and documenting of test equipment into calibration facilities [16].


MECHANICAL SCANNING

The reflector, its feed source, or the entire antenna is moved in a desired
pattern [18].


MECHANICAL-ROTATION FREQUENCY

The speed in revolutions per minute of armatures in electric motors and engine-driven generators; blade speed in turbines [16].


MECHANIZATION

Using electric or electro-mechanical switches to represent logic circuits (AND, OR, NOT, NOR, NAND) [13].


MEDIUM

The vehicle through which a wave travels from one point to the next. Air, water, and wood are examples [10].


MEDIUM ALTITUDE ORBIT

An orbit from 2,000 to 12,000 miles above the earth. The rotation rate of
the earth and satellite are quite different, and the satellite moves quickly across the sky [17].


MEDIUM FREQUENCY

The band of frequencies from 300 kHz to 3 MHz [17].

MEGA

A prefix meaning one million; also MEG [1].

MEGGER

Common name for a megohmmeter [3] [16].

MEGOHMMETER

A meter that measures very large values of resistance; usually used to check for
insulation breakdown in wires [3].


METALLIC ARMOR

A protective covering for wires or cables. Made as a woven wire braid, metal
tape, or interlocking metal cover. Made from steel, copper, bronze, or aluminum [4].


METALLIC INSULATOR

A shorted quarter-wave section of transmission line [11].

METALLIC RECTIFIER

Also known as a DRY-DISC RECTIFIER. A metal-to-semiconductor, large-
area, contact device in which a semiconductor is sandwiched between two metal plates. This asymmetrical construction permits current to flow more readily in one direction than the other [7].


METER

A device used to measure a specific quantity, such as current, voltage, or frequency [3].

METER MOVEMENT

The part of the meter that moves to indicate some value [3] [16].

METER SHUNT

A resistor placed in parallel with the meter terminals; used to provide increased range capability [16].


MHO

Unit of conductance; the reciprocal of the ohm [1].

MICRO

A prefix meaning one-millionth [1].

MICROCIRCUIT

A small circuit having high equivalent-circuit-element density, which is considered as a single part composed of interconnected elements on or within a single substrate to perform an electronic-circuit function [14].


MICROCIRCUIT MODULE

An assembly of microcircuits or a combination of microcircuits and
discrete components that perform one or more distinct functions [14].


MICROELECTRONICS

The solid-state concept of electronics in which compact semiconductor
materials are designed to function as an entire circuit or subassembly rather than as circuit components [7] [14].


MICROPHONE

An energy converter that changes sound energy into electrical energy [12].

MICROWAVE REGION

The portion of the electromagnetic spectrum from 1,000 MHz to 100,000 MHz
[11].


MIL

The diameter of a conductor equal to 1/1000 (.001) inch [4].

MIL FOOT

A unit of measurement for conductors (diameter of 1 mil, 1 foot in length.) [4].

MILITARY SPECIFICATIONS

Technical requirements and standards adopted by the Department of Defense that must be met by vendors selling materials to DOD [4].


MILITARY STANDARDS

Standards of performance for components or equipment that must be met to be acceptable for military systems [14].


MILLI

A prefix meaning one-thousandth [1].

MINIATURE ELECTRONICS

Modules, packages, pcbs, and so forth, composed exclusively of discrete
components [14].


MINIMUM DISCERNIBLE SIGNAL

The weakest input signal that produces a usable signal at the output of a receiver. The weaker the input signal, the more sensitive the receiver [18].


MINOR LOBE

The lobe in which the radiation intensity is less than that of a major lobe [10].

MINORITY CARRIERS

Either electrons or holes, whichever is the less dominant carrier in a
semiconductor device. In P-type semiconductors, electrons are the minority carriers; in N-type semiconductors, the holes are the minority carriers [7].


MINORITY CURRENT

A very small current that passes through the base-to-collector junction when
this junction is reverse biased [7].


MIXER

In radar, a circuit that combines the received RF signal with a local-oscillator signal to effectively convert the received signal to a lower IF frequency signal [18].


MODE SHIFTING

In a magnetron, the inadvertent shifting from one mode to another during a pulse [18].


MODE SKIPPING

Operation in which the magnetron fires randomly, rather than firing on each
successive pulse as desired [18].


MODIFIED TRANSISTOR OUTLINE

An IC package resembling a transistor [14].

MODULAR CIRCUITRY

A technique where printed circuit boards are stacked and connected together
to form a module [7].


MODULAR PACKAGING

Circuit assemblies or subassemblies packaged to be easily removed for
maintenance or repair [14].


MODULATED WAVE

A complex wave consisting of a carrier and a modulating wave that is
transmitted through space [12].


MODULATING WAVE

An information wave representing intelligence [12].

MODULATION

The process of impressing intelligence upon a transmission medium, such as radio waves [12].


MODULATION FACTOR

(M)—An indication of relative magnitudes of the RF carrier and the
modulating signal [12].


MODULATION INDEX

The ratio of frequency deviation to the frequency of the modulating signal [12].

MODULATOR

(1) A device that produces modulation; that is, a device that varies the amplitude, frequency, or phase of an ac signal [11] [12]. (2) A circuit used in servosystems to convert a dc signal to an ac signal. The output ac signal is a sine wave at the frequency of the ac reference voltage. The amplitude of the output is directly related to the amplitude of the dc input. The circuit's function is opposite to that of a DEMODULATOR [15]. (3) In radar, it produces a high-voltage pulse that turns the transmitter on and off [18].


MODULATOR SWITCHING DEVICE

Controls the on (discharge) and off (charge) time of the modulator [18].


MODULE

A circuit or portion of a circuit packaged as a removable unit. A separable unit in a packaging scheme displaying regularity of dimensions [14].


MOISTURE LAPSE

Abnormal variation of moisture content at different altitudes because of high
moisture located just above large bodies of water [18].


MONOLITHIC CIRCUIT

A circuit where all elements (resistors, transistors, and so forth) associated
with the circuit are fabricated inseparably within a continuous piece of material (called the substrate), usually silicon [7].


MONOLITHIC IC

ICs that are formed completely within a semiconductor substrate. Silicon chips [14].

MONOPULSE (SIMULTANEOUS) LOBING

A radar receiving method using two or more (usually four) partially overlapping lobes. Sum and difference locate the target with aspect to the axis of the
antenna [18].


MONOPULSE RADAR

A radar that gets the range, bearing, and elevation position data of a target from a single pulse [18].


MONOPULSE RECEIVER

See MONOPULSE RADAR [18].

MONOSTABLE MULTIVIBRATOR

A multivibrator that has one steady state. A signal (trigger) must be applied to cause change of states [9].


MOSFET

METAL-OXIDE SEMICONDUCTOR FIELD-EFFECT TRANSISTO. A semiconductor device that contains diffused source and drain regions on either side of a P- or
N-channel area. Also contains a gate insulated from the channel area by silicon-oxide. Operates in either the depletion or the enhancement mode [7].

MOST SIGNIFICANT DIGIT

The MSD is the digit whose position within a given number expression has the greatest weighting power [13].


MOTOR

A machine that converts electrical energy to mechanical energy. It is activated by ac or dc voltage, depending on the design [5].


MOTOR LOAD

Any device driven by a motor. Typical loads are drills, saws, water pumps, rotating antennas, generators, and so forth. The speed and power capabilities of a motor must be matched to the speed and power capabilities of the motor load [5].


MOTOR REACTION

The force created by generator armature current that tends to oppose the normal rotation of the armature [5].


MOTOR STARTERS

Large resistive devices placed in series with dc motor armatures to prevent the
armature from drawing excessive current until armature speed develops counter emf. The resistance is gradually removed from the circuit either automatically or manually as motor speed increases [5].


MOVING TARGET INDICATOR

A device that limits the display of radar information to moving targets [18].


MOVING-IRON METER MOVEMENT

Same as MOVING-VANE METER MOVEMENT [3].

MOVING-VANE METER MOVEMENT

A meter movement that uses the magnetic repulsion of the like poles created in two iron vanes by current through a coil of wire; most commonly used movement for ac meters [3].


MSD

See MOST SIGNIFICANT DIGIT [13].

MTDS

An abbreviation for the marine tactical data system [17].

MU

Symbol for amplification factor [6] [7].

MULTICONDUCTOR

More than one conductor, as in a cable [4].

MULTICOUPLERS

Couplers that patch receivers or transmitters to antennas. They also filter out
harmonics and spurious responses and impedance-match the equipment [17].


MULTIELECTRODE TUBE

An electron tube normally classified according to its number of electrodes
(the multielectrode tube contains more than three electrodes) [6].


MULTIELEMENT ARRAY

An array that consists of one or more arrays and is classified as to directivity [10].


MULTIELEMENT PARASITIC ARRAY

An array that contains two or more parasitic elements and a driven element [10].


MULTILOOP SERVOSYSTEM

A servosystem that contains more than one servo loop; each loop is designed to perform its own function [15].


MULTIMETER

A single meter combining the functions of an ammeter, a voltmeter, and an ohmmeter [3].


MULTIPATH

The multiple paths a radio wave may follow between transmitter and receiver [10].

MULTIPHASE

See POLYPHASE [5].

MULTIPLEXING

A method for simultaneous transmission of two or more signals over a common
carrier wave [17].


MULTIPLICATION FACTOR

The number of times an input frequency is multiplied [12].

MULTISPEED SYNCHRO SYSTEMS

Systems that transmit data at different transmission speeds; for example, dual-speed and tri-speed synchro systems [15].


MULTIUNIT TUBE

An electron tube containing two or more units within the same envelope. The
multiunit tube is capable of operating as a single-unit tube, or each unit can operate as a separate tube [6].


MULTIVIBRATOR

A form of relaxation oscillator which comprises two stages that are coupled so that the input of one is derived from the output of the other [9] [13].


MULTIVIBRATOR MODULATOR

An astable multivibrator used to provide frequency modulation. The modulating af voltage is inserted in series with the base return of the multivibrator transistors to produce the frequency modulation [12].


MUTUAL FLUX

The total flux in the core of a transformer that is common to both the primary and secondary windings. The flux links both windings [2].


MUTUAL INDUCTANCE

A circuit property existing when the relative position of two inductors causes
the magnetic lines of force from one to link with the turns of the other. The symbol for mutual inductance is M [2].



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