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P

PACKAGING LEVELS

A system developed to assist maintenance personnel in determining the
repairability of components, printed circuit boards, modules, and so forth [14].


PAGE PRINTER

A high-speed printer that prints teletypewriter characters one at a time in a full-page format [17].


PARABOLIC REFLECTOR

An antenna reflector in the shape of a parabola. It converts spherical
wavefronts from the radiating element into plane wavefronts [18].


PARALLAX ERROR

The error in meter readings that results when you look at a meter from some
position other than directly in line with the pointer and meter face. A mirror mounted on the meter face aids in eliminating parallax error [3].


PARALLEL CIRCUIT

Two or more electrical devices connected to the same pair of terminals so
separate currents flow through each; electrons have more than one path to travel from the negative to the positive terminal [1].


PARALLEL LIMITER

A resistor and diode, connected in series with the input signal, in which the
output is taken across (parallel to) the diode [9].


PARALLEL-CONNECTED DUPLEXER

Configuration in which the tr spark gap is connected across the two legs of the transmission line one-quarter wavelength from the T-junction [18].


PARALLEL-NEGATIVE LIMITER

A resistor and diode, connected in series with the input signal, in which the output is taken across the diode and the negative alternation is eliminated [9]


PARALLEL-POSITIVE LIMITER

A resistor and diode connected in series with the input signal, in which the output is taken across the diode and the positive alternation is eliminated [9].


PARALLEL-RESONANT CIRCUIT

A resonant circuit in which the source voltage is connected across
a parallel circuit (formed by a capacitor and an inductor) to furnish a high impedance to the frequency at which the circuit is resonant. Often referred to as a tank circuit [9] [10].


PARALLEL-WIRE

A type of transmission line consisting of two parallel wires [10].

PARASITIC ARRAY

An antenna array containing one or more elements not connected to the
transmission line [10] [18].


PARASITIC ELEMENT

The passive element of an antenna array that is connected to neither the
transmission line nor the driven element [10].


PART

A part is one component or two or more components joined together. It is not normally subject to disassembly without destruction [17].


PASSIVE SATELLITE

A satellite that reflects radio signals back to earth [17].

PATCH PANEL

A panel used to tie a receiver or transmitter to its associated equipment [17].

PEAK AMPLITUDE

The maximum value above or below the reference line [12].

PEAK CURRENT

The maximum current that flows during a complete cycle [6].

PEAK DETECTION

Detection that uses the amplitude of pam or the duration of pdm to charge a holding capacitor and restore the original waveform [12]


PEAK POWER

The maximum value of the transmitted pulse [12].

PEAK VALUE

The maximum instantaneous value of a varying current, voltage, or power. It is equal to 1.414 times the effective value of a sine wave [2].


PEAK VOLTAGE

The maximum value present in a varying or alternating voltage. This value may be positive or negative [6].


PEAK-REVERSE VOLTAGE

The peak ac voltage that a rectifier tube will withstand in the reverse
direction [6].


PEAK-TO-PEAK

The measure of absolute magnitude of an ac waveform, measured from the greatest positive alternation to the greatest negative alternation [2].


PEAKING COIL

An inductor used in an amplifier to provide high-frequency compensation, which extends the high-frequency response of the amplifier [8].


PENTAVALENT IMPURITY

A type of impurity that contains five valence electrons and donates one
electron to the doped material. Also called DONOR IMPURITY [7].


PENTODE TUBE

A five-electrode electron tube containing a plate, a cathode, a control grid, and two grids [6].


PERCENT OF MODULATION

The degree of modulation defined in terms of the maximum permissible
amount of modulation [12].


PERFORATOR

A device that stores a teletypewriter message on a paper tape [17].

PERIGEE

The point in the orbit of a satellite closest to the earth [17].

PERIOD TIME

The time required to complete one cycle of a waveform [2] [10] [12].

PERIODIC WAVE

A waveform that undergoes a pattern of changes, returns to its original pattern, and then repeats the same pattern of changes. Examples are square waves, rectangular waves, and sawtooth waves [9].


PERMANENT MAGNET SPEAKER

A speaker with a permanent magnet mounted on soft iron pole pieces [17].


PERMEABILITY

The measure of the ability of a material to act as a path for magnetic lines of force [1] [8].


PERSISTENCE

The length of time a phosphor dot glows on a CRT before disappearing [6] [18].

PHANTASTRON

A variable-length sawtooth generator often used to produce a sweep on an A-scope [18].


PHASE

The angular relationship between two alternating currents or voltages when the voltage or current is plotted as a function of time. When the two are in phase, the angle is zero; both reach their peak simultaneously. When out of phase, one will lead or lag the other; that is, at the instant when one is at its peak, the other will not be at peak value and (depending on the phase angle) may differ in polarity as well as magnitude [2].


PHASE ANGLE

The number of electrical degrees of lead or lag between the voltage and current waveforms in an ac circuit [2] [12].


PHASE MODULATION

(pm)—Angle modulation in which the phase of the carrier is controlled by the
modulating waveform. The amplitude of the modulating wave determines the amount of phase shift, and the frequency of the modulation determines how often the phase shifts [12].


PHASE SHIFTER

A device used to change the phase relationship between two ac signals [11].

PHASE SPLITTER

A device that provides two output signals from a single input signal. The two output signals differ from each other in phase (usually by 180 degrees) [8].


PHASE-SHIFT DISCRIMINATOR

See FOSTER-SEELEY DISCRIMINATOR [12].

PHASE-SHIFT KEYING

Similar to ON-OFF cw keying in AM systems and frequency-shift keying in
FM systems. Each time a mark is received, the phase is reversed. No phase reversal takes place when a space is received [12].


PHOSPHOR

The material used to convert the energy of electrons into visible light [6].

PHOTOCELL

A light-controlled variable resistor which has a light-to-dark resistance ratio of 1:1000. Used in various types of control and timing circuits [7].


PHOTODIODE

A light-controlled PN junction. Current flow increases when the PN junction is exposed to an external light source [7].


PHOTOELECTRIC VOLTAGE

A voltage produced by light [1].

PHOTOETCHING

Chemical process of removing unwanted material in producing printed circuit boards [14].


PHOTOTRANSISTOR

An optoelectronic device that conducts current when exposed to light. Produces more current and is much more sensitive to light than the photodiode [7].


PHOTOVOLTAIC CELL

(SOLAR CELL)—A device that acts much like a battery when exposed to
light and converts light energy into electrical energy [7].


PICO

A prefix adopted by the National Bureau of Standards meaning 10 -12 [1].

PICTORIAL DIAGRAM

A diagram showing actual pictorial sketches of the various parts of an
equipment and the electrical connections between the parts [4].


PIEZOELECTRIC EFFECT

The effect of producing a voltage by placing a stress, either by compression, expansion, or twisting, on a crystal and, conversely, producing a stress in a crystal by applying a voltage to it [1].


PIP

PIP (BLIP)—On a CRT display, a spot of light or a baseline irregularity representing the radar echo [18].

PITCH

A term used to describe the frequency of a sound heard by the human ear [10].

PLANAR TUBE

An electron tube, constructed with parallel electrodes and a ceramic envelope, that is used at uhf frequencies. It is commonly referred to as a lighthouse tube [6].


PLANE OF POLARIZATION

The plane (vertical or horizontal), with respect to the earth, in which the
E field propagates [10].


PLANE WAVEFRONTS

Waves of energy that are flat, parallel planes and are perpendicular to the
direction of propagation [18].


PLANNED-POSITION INDICATOR

A radar display in which range is indicated by the distance of a bright spot or pip from the center of the screen and the bearing is indicated by the radial angle of the spot [18].


PLATE

(1) One of the electrodes in a storage battery [1]. (2) One of the electrodes in a capacitor [2]. (3) The principal electrode to which the electron stream is attracted in an electron tube [6].


PLATE DISSIPATION

The amount of power lost as heat in the plate of a vacuum tube [6].

PLATE KEYING

A keying system in which the plate supply is interrupted [12].

PLATE MODULATOR

An electron-tube modulator in which the modulating voltage is applied to the
plate circuit of the tube [12].


PLATE RESISTANCE

The plate voltage change divided by the resultant plate current change in a
vacuum tube, all other conditions being fixed [6].


POINT BENDER

A tool used to adjust the contact spacing on a relay [3].

POINT OF ZERO DISPLACEMENT

See REFERENCE LINE [10].

POINT-CONTACT DIODE

A diode in which the end of a fine wire is pressed against a semiconductor.
Used as a detector or mixer over the microwave region [7].


POINT-TO-POINT WIRING

Individual wires run from terminal to terminal to complete a circuit [14].

POLAR

The teletypewriter operation in which current flow of one polarity represents a mark, and current of the opposite polarity represents a space [17].


POLAR ORBIT

An orbit that has an angle of inclination of or near 90 degrees [17].

POLAR-COORDINATE GRAPH

A graph with a pair of axes. One consists of a series of circles with a
common center, and the other consists of a rotating radius extending from the center of the concentric circles [10].


POLARITY

(1) The condition in an electrical circuit by which the direction of the flow of current can be determined. Usually applied to batteries and other direct voltage sources. (2) Two opposite charges, one positive and one negative. (3) A quality of having two opposite magnetic poles, one north and the other south [1] [13].


POLARIZATION

(1) The effect of hydrogen surrounding the anode of a cell, which increases the
internal resistance of the cell [1]. (2) The magnetic orientation of molecules in a magnetizable material in a magnetic field, whereby tiny internal magnets tend to line up in the field [2].


POLE

(1) The number of points at which current can enter a switch; for example, single pole, double pole, and three pole [3]. (2) The sections of a field magnet where the flux lines are concentrated; also where they enter and leave the magnet [5].


POLE PIECE

(1) A piece of ferromagnetic material used to control the distribution of magnetic lines of force; that is, it concentrates the lines of force in a particular place or evenly distributes the lines of force over a wide area [3]. (2) The shaped magnetic material upon which the stator windings of motors and generators are mounted or wound [5].


POLYMER FUME FEVER

A flu-like condition caused by a person breathing the vapors of fluorocarbons when they are heated. Sometimes called FOUNDRYMAN'S FEVER [4].


POLYPHASE

A term that describes systems or units of a system that are activated by or which generate separate out-of-phase voltages. Typical polyphase systems are 2-phase and 3-phase; their voltages are 90- and 120-degrees out of phase, respectively. This term means the same as MULTIPHASE [5].


POSITION SENSOR

A component in a servosystem that measures position and converts the
measurement into a form convenient for transmission as a feedback signal [15].


POSITION SERVOSYSTEM

A servosystem whose end function is to control the position of the load it
is driving [15].


POSITIONAL NOTATION

A numbering system in which a number is represented by means of a stated
set of symbols or digits, such that the value contributed by each symbol or digit depends upon its position as well as upon its value [13].


POSITIONAL WEIGHTING

The value given a digit based on the digit's position within a given number
[13].


POSITIVE ALTERNATION

The part of a sine wave that is above the reference line [2] [10] [12].

POSITIVE CLAMPER

A circuit that clamps the lower extremity of the output waveshape to a dc
potential of 0 volts [9].


POSITIVE FEEDBACK

Feedback in which the feedback signal is in phase with the input signal. Also
called REGENERATIVE FEEDBACK [8].


POSITIVE LOGIC

The form of logic in which the more positive logic level represents 1 and the more negative level represents 0 [13].


POSITIVE TEMPERATURE COEFFICIENT

The characteristic of a conductor in which the resistance increases as temperature increases [7].


POTENTIAL ENERGY

Energy caused by the position of one body with respect to another body or to
the relative parts of the same body [1].


POTENTIOMETER

A variable resistor, used as a position sensor in servosystems, having a terminal
connected to each end of a resistive element and a third terminal connected to a wiper contact. The output is a voltage that is variable depending upon the position of the wiper contact. The potentiometer is commonly referred to as a variable voltage divider. It, in effect, converts mechanical information into
an electrical signal [1] [15].


POWER

The rate of doing work or the rate of expending energy. The unit of electrical power is the watt [1].


POWER AMPLIFIER

An amplifier in which the output-signal power is greater than the input-signal
power [8].


POWER FACTOR

The ratio of the actual power of an alternating or pulsating current, as measured by a wattmeter, to the apparent power, as indicated by ammeter and voltmeter readings. The power factor of an inductor, capacitor, or insulator is an expression of their losses [2] [16].


POWER GAIN

In an antenna, the ratio of its radiated power to that of a reference [11] [18].

POWER LOSS

(1) The electrical power, supplied to a circuit, that does no work and is usually dissipated as heat [2] [4]. (2) The heat loss in a conductor as current flows through it [10].


POWER PENTODE

A special purpose tube used to provide high-current gain or power mplification.
Each grid wire is directly in line with the one before and after it, a fact which allows more electrons to reach the plate [6].


POWER RATIO

See POWER GAIN [11].

POWER STANDING-WAVE RATIO

The ratio of the square of the maximum and minimum voltages of a transmission line [10].


POWER SUPPLY

A unit that supplies electrical power to another unit. It changes ac to dc and maintains a constant voltage output within limits [6] [7].


POWER-AMPLIFIER TRANSMITTER

Transmitter that uses a series of power amplifiers to create a high level of power [18].


PREAMPLIFIER

An amplifier that raises the output of a low-level source for further processing without appreciable degradation of the signal-to-noise ratio [18].


PRECESSION

The rotation of the spin axis of a gyro in response to an applied force. The direction of precession is always perpendicular to the direction of applied force [15].


PRECESSION VECTOR

In a gyro, a vector representing the angular change of the spin axis when
torque is applied. The precession vector represents the axis about which precession occurs [15].


PRESTANDARD NAVY SYNCHROS

Synchros that are designed to meet Navy, rather than servicewide, specifications [15].


PREVENTIVE MAINTENANCE

Visual, mechanical, electrical, and electronic checks that are made to
determine whether or not equipment is functioning properly [16].


PRIMARIES

PRIMARIES (OF LIGHT)—The three primary colors of light from which all other colors can be derived. The colors are red, green, and blue [10].


PRIMARY CELL

An electrochemical cell in which the chemical action eats away one of the electrodes, usually the negative electrode [1].


PRIMARY LOOP

In a cooling system, the primary source of cooling for the distilled water [18].

PRIMARY WINDING

The winding of a transformer connected to the electrical source [2].

PRIME MOVER

The source of the turning force applied to the rotor of a generator. This may be an electric motor, a gasoline engine, a steam turbine, and so forth [5].


PRINTED CIRCUIT BOARD

A flat, insulating surface upon which printed wiring and miniaturized
components are connected in a predetermined design and attached to a common base [7] [14].


PRISM

A triangular-shaped glass that refracts and disperses light waves into component wavelengths [10].


PROBE COUPLER

A resonant conductor placed in a waveguide or cavity to insert or extract energy [18].


PROGRAMMED TRACKING

The method that uses known satellite orbital parameters to generate antenna pointing angles [17].


PROPAGATION

Waves traveling through a medium [10].

PULSE

Signal characterized by a steep rise from and decay toward an initial level [9] [12].

PULSE DURATION

PULSE DURATION (PD)—The period of time during which a pulse is present [12].

PULSE MODULATION

A form of modulation in which one of the characteristics of a pulse train is
varied [12].


PULSE OSCILLATOR

A sine-wave oscillator that is turned on and off at specific times. Also known as
a ringing oscillator [9].


PULSE WIDTH

Duration of time between the leading and trailing edges of a pulse [12] [18].

PULSE-AMPLITUDE MODULATION

PULSE-AMPLITUDE MODULATION (PAM)—Pulse modulation in which the amplitude of the pulses is varied by the modulating signal [12].


PULSE-CODE MODULATION

PULSE-CODE MODULATION (PCM)—A modulation system in which the standard values of a quantized wave are indicated by a series of coded pulses [12].


PULSE-DURATION MODULATION

PULSE-DURATION MODULATION (PDM)—Pulse modulation in which the time duration of the pulses is changed by the modulating signal [12].


PULSE-FORMING NETWORK

PULSE-FORMING NETWORK (PFN)—An lc network that alternately stores and releases energy in an approximately rectangular wave [12] [18].


PULSE-FREQUENCY MODULATION

PULSE-FREQUENCY MODULATION (PFM)—Pulse modulation in which the modulating voltage varies the repetition rate of a pulse train [12].


PULSE-POSITION MODULATION

PULSE-POSITION MODULATION (PPM)—Pulse modulation in which the position of the pulses is varied by the modulating voltage [12].


PULSE-REPETITION FREQUENCY

PULSE-REPETITION FREQUENCY (PRF)—The rate, in pulses per second, at which the pulses occur [9] [12] [18].


PULSE-REPETITION RATE

PULSE-REPETITION RATE (PRR)—Same as PULSE-REPETITION FREQUENCY (PRF) [9] [12] [18].


PULSE-REPETITION TIME

PULSE-REPETITION TIME (PRT)—Interval between the start of one pulse and the start of the next pulse; reciprocal of pulse-repetition frequency [18].


PULSE-TIME MODULATION

PULSE-TIME MODULATION (PTM)—Pulse modulation that varies one of the time characteristics of a pulse train (pwm, pdm, ppm, or pfm) [12].


PULSE-WIDTH MODULATION

PULSE-WIDTH MODULATION (PWM)—Pulse modulation in which the duration of the pulses is varied by the modulating voltage [12].


PULSING

Allowing oscillations to occur for a specific period of time only during selected intervals [12].

PUMP

Electrical source of the energy required to vary the capacitance of a parametric amplifier [11].

PUSH-PULL AMPLIFIER

An amplifier that uses two transistors (or electron tubes) whose output signals are in phase opposition [8].



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