<<

. 30
( 42)



>>




Y
PL Abbreviation for PRIVATE LINE. and POLARIZED LIGHT).
place effect An apparent change in the perceived plane-polarized light See POLARIZATION, 3 and




FL
pitch of a sound, caused by variations in the way POLARIZED LIGHT.
the waves interact inside the human ear. plane-reflector antenna A directive antenna in
planar diffusion In the production of a semicon- which the reflector is a sheet of metal or a metal
ductor device, the diffusion of all the elements screen. In a corner-reflector antenna, the reflec-
AM
into one face of a wafer. Consequently, connec- tor is a folded sheet, or two sheets joined along
tions to the elements all lie in one plane. Also see one edge.
EPITAXIAL PLANAR TRANSISTOR and PLANAR planetary electron See ORBITAL ELECTRON.
TRANSISTOR. planimeter A mechanical instrument for measur-
planar diode A semiconductor diode, having a pn ing the area of a closed figure. The outline of the
TE

junction that lies entirely within a single plane. figure is traced with the pointer of the device, and
planar epitaxial passivated diode A junction the area is read from a pair of dials. In this appli-
diode that, like the planar epitaxial transistor, cation, the planimeter does the work of integral
has been manufactured by planar diffusion, then calculus.
passivated to protect the junction. Also see EPI- PLANNER A high-level computer programming
TAXIAL GROWTH, EPITAXY, PASSIVATION, and language sometimes used in artificial intelli-
PLANAR DIFFUSION. gence. It is a “goal-oriented” language in that it
PL/1 A computer programming language that is a seeks a solution to a problem using various
hybrid of scientific and commercial types (like AL- schemes, as necessary.
GOL and COBOL), the combined features be- plan position indicator Abbreviation, PPI. A radar
ing powerful problem-solving and mass-data- display on whose screen small spots of light re-
handling abilities. construct the scanned vicinity, revealing objects,
planar epitaxial passivated transistor A planar such as buildings, boats, aircraft, etc. The dis-
epitaxial transistor that has been passivated to tance from the center of the screen to a spot de-
protect the exposed junctions. Also see EPITAX- picts the range of an object, and the radial angle
IAL PLANAR TRANSISTOR, PLANAR TRANSIS- reveals its bearing.
TOR, EPITAXIAL TRANSISTOR, PASSIVATION, plant In computer operations, to put the result of
and PLANAR TRANSISTOR. an operation specified by a routine in a storage
planar transistor A transistor in which the emit- location from which it will be taken for implemen-
ter, base, and collector elements terminate on the tation of an instruction further on in the pro-
same face (plane) of the silicon wafer. A thin film gram.
of silicon dioxide is grown on top of the wafer to plaque resistor A flat, noninductive, power resis-
insulate the exposed junctions after the leads tor, often used as a dummy load during high-
have been attached (i.e., the transistor is passi- frequency power measurements.
vated). plasma A usually high-temperature gas that is so
Planck constant Symbol, h. Unit, joule-second. highly ionized that it is electrically conductive
The constant of proportionality in the fundamen- and susceptible to magnetic fields; it is recog-
tal law of the quantum theory, stating that nized as one of the states of matter. Also see
radiant energy is composed of quanta propor- PHYSICAL PROPERTIES.
tional to the frequency of the radiation; h = q/f = plasma diode A diode in which a plasma sub-
6.62608 — 10“34 J•s, where q is the value of the stance produces conduction in one direction, but
quantum and f is the frequency in Hz. not in the other.




Team-Fly®
537
plasma length • plated magnetic wire


y
plasma length See DEBYE LENGTH.
plasma oscillation In a plasma, a form of electric-
field oscillation of the rapidly moving electrons. Plateau




{
plasma torch A torch, used for such high-heat ap-
plications as melting metal, in which a gas is
heated by electricity to the high temperature at
which it becomes a plasma.
plasmatron A form of amplifier tube sometimes
used at ultra-high and microwave frequencies. It
is similar to a thyratron. An inert gas is excited
until it becomes a plasma, producing amplifica-
tion under certain operating conditions. y = f (x)
Plastacele See CELLULOSE ACETATE.
plastic A synthetic material usually made from
various organic compounds through polymeriza-
tion (see POLYMERIZE). Plastics can be molded
into solid shapes and are available as films. Ex-
amples: celluloid, cellulose acetate, cellulose ni-
x
trate, polyethylene, and polystyrene. Also see
THERMOPLASTIC MATERIAL and THERMOSET-
plateau
TING MATERIAL.
plastic-film capacitor A capacitor made using
polyester, polyethylene, or polystyrene. The
method of manufacture is similar to that for pa- plate capacitance See PLATE-CATHODE CAPACI-
per capacitors when the plastic is flexible. Stack- TANCE.
ing methods can be used if the plastic is more plate-cathode capacitance Symbol, CPK. Unit, pF.
rigid. The geometries can vary, and these capaci- The internal capacitance between the plate and
tors are therefore found in several different cathode of an electron tube. Also called OUTPUT
shapes. Capacitance values for plastic-film units CAPACITANCE.
range from about 50 pF to several tens of micro- plate characteristic For an electron tube, the fam-
farads. Most often they are in the range of 0.001 µF ily of plate current-vs-plate voltage curves for var-
to 10 µF. Plastic-film capacitors are employed in ious grid-bias voltages.
audio equipment, and also in wireless transmit- plate circuit The external circuit associated with
ters and receivers. The efficiency is good, al- the plate of an electron tube.
though not as high as that for mica-dielectric plate-circuit relay A direct-current relay operated
units. Compare CERAMIC CAPACITOR, ELEC- in series with the plate of an electron tube.
TROLYTIC CAPACITOR, MICA CAPACITOR, PA- plate conductance Symbol, gP. Unit, siemens.
PER CAPACITOR, TANTALUM CAPACITOR. Conductance of the internal plate circuit of an
plasticizer A substance added to a plastic to make electron tube. The value of static gP is equal to the
it softer or more flexible. plate current divided by the plate voltage (IP/EP).
plastic-leaded chip carrier Abbreviated PLCC. A The value of dynamic gP is equal to the derivative
surface-mounted package for an integrated cir- of the static gP: dIP/dEP. Plate conductance is the
cuit. It is small in size and has high electrical and reciprocal of PLATE RESISTANCE.
mechanical reliability. plate current Symbol, IP. Direct current flowing in
plate 1. The anode of an electron tube. 2. One of the plate circuit of an electron tube.
the electrodes of a primary or secondary battery plate-current shift A change in the plate current
cell. 3. One of the electrodes of a capacitor. of a radio-frequency power amplifier during am-
plateau In a response curve, a region in which an plitude modulation. The action discloses faulty
increase in the independent variable produces no operation because the average plate current
further change in the dependent variable. Exam- should remain constant during modulation.
ple: the saturation region in a common-base plate dissipation Abbreviation, PD. Unit, watt.
transistor collector-current curve. Power expended in the plate of an electron tube.
plate blocking capacitor A capacitor connected For an unloaded tube, PD = EPIP, where EP is the
between the plate of an electron tube and the direct-current (dc) plate voltage in volts, and IP is
plate tank. It allows the direct-current supply the dc plate current in amperes. For a loaded
voltage to be applied directly to the plate without tube, PD = Po “ Pi, where Po is the alternating-
it passing through the tank coil, while at the current (ac) power output of an amplifier or
same time preventing the tank coil from short- oscillator in which the tube operates, and Pi is the
circuiting the plate power supply. The capacitor dc plate power input.
freely transmits alternating-current signal energy plated magnetic wire A wire with a ferromagnetic
to the tank. outer coating on a core that is not magnetic.
538 plated-wire memory • plate-type capacitor


plated-wire memory See WIRE MEMORY. plate-screen modulation A method of AMPLI-
plate-grid capacitance Symbol, CPG or CGP. Unit, TUDE MODULATION in which the modulating
pF. The internal capacitance between the plate voltage is superimposed simultaneously on the
and control grid of an electron tube. Also called direct-current plate and screen voltages of a
INTERELECTRODE CAPACITANCE and FEED- higher-frequency amplifier or oscillator.
BACK CAPACITANCE. plate series compensation In an audio amplifier,
plate load The power-consuming load into which the use of a plate decoupling circuit to obtain a
the plate circuit of an electron tube operates. In fixed amount of bass boost.
an intermediate stage of a multistage amplifier, plate shunt compensation The addition of a net-
this load is the grid circuit of the following tube. work to the plate-output circuit of a tube to boost
plate load impedance Symbol, ZLP. Unit, ohm. In a the bass response of an amplifier.
tube circuit, the (output) impedance that is ac- plate spacing 1. The distance between plates in a
connected between the plate and ground, or dc- fixed capacitor. This dimension is usually the
connected between the plate electrode and dc same as dielectric thickness. 2. The distance be-
plate power supply. tween plates in a variable capacitor. Also called
plate meter A direct-current ammeter or mil- capacitor air gap.
liammeter that indicates the plate current of an
electron tube. Plate
plate modulation A method of AMPLITUDE MOD-
ULATION in which a modulating voltage is super-
imposed on the direct-current plate voltage of a
higher-frequency amplifier or oscillator.
platen The “roller” in a teletypewriter or impact Plate
spacing
printer. It supports the paper against impact by Dielectric
the print head; it also helps to move the paper
through the machine.
plate-neutralized amplifier A vacuum-tube radio-
frequency power amplifier in which a neutralizing
capacitor is connected between the control grid Plate
and the free end of a center-tapped plate-tank
coil.
plate power Symbol, PP. Unit, watt. Power in the
plate circuit of an electron tube; PP = EPIP, where
EP is the plate voltage in volts and IP is the plate
plate spacing, 1
current in amperes.
plate power input See PLATE POWER.
plate power output The output signal power deliv- plate supply voltage Symbol, EBB. The output volt-
ered by the plate circuit of an electron tube. Com- age of a plate power supply.
pare PLATE POWER INPUT. plate tank A resonant inductance-capacitance
plate power supply The (usually direct current) (LC) circuit operated from the plate of an electron
power supply that furnishes energy to the plate of tube.
an electron tube. plate tank capacitance The capacitance required
plate pulse modulation A method of obtaining to tune a PLATE TANK to resonance.
pulse modulation by injecting high-voltage pulses plate tank inductance The inductance of the coil
into the plate circuit of a vacuum-tube amplifier. in a PLATE TANK.
plate relay A relay operated in series with the plate plate tank Q Figure of merit (see Q) of a plate tank,
of an electron tube. a function of the load resistance and the tank in-
plate resistance Symbol, rP. Unit, ohm. Resistance ductance-to-capacitance (L/C) ratio.
of the internal plate circuit of an electron tube. plate tank voltage The audio-frequency or radio-
The static value of rP is equal to EP/IP, where EP is frequency voltage developed across the plate tank
the plate voltage in volts, and IP is the plate cur- of an electron-tube circuit.
rent in amperes. The dynamic value is dEP/dIP. plate tuning Tuning an electron-tube circuit by
plate saturation In an electron tube, the point at varying the capacitance, inductance, or both in
which, while plate voltage is increasing, the plate the plate tank.
attracts all the electrons emitted by the cathode plate tuning capacitance See PLATE TANK CA-
(i.e., the point beyond which no further signifi- PACITANCE.
cant increase in plate current results from a fur- plate tuning inductance See PLATE TANK IN-
ther increase in plate voltage). DUCTANCE.
plate-screen capacitance Symbol, CPS. Unit, pF. plate-type capacitor A capacitor having flat metal
The internal capacitance between the plate and plates, rather than concentric cylinders, a cylin-
screen grid of an electron tube. der and rod, etc.
539
plate voltage • plug-in meter


plate voltage Symbol, EP. The direct-current volt- PLO Abbreviation of PHASE-LOCKED OSCILLA-
age applied to the plate of an electron tube. TOR.
plate winding 1. An inductor connected in series plot 1. A curve depicting the variations of one
between the plate of a vacuum tube and the pos- quantity, with respect to another. 2. To generate,
itive power-supply voltage. 2. The primary wind- print, or display a curve of the type defined in 1.
ing of a plate-circuit output transformer. plotter A machine that plots (see PLOT, 2) auto-
platiniridium A natural alloy of PLATINUM and matically, often by the direction of a computer.
IRIDIUM. PL tone encoder An audio oscillator and modula-
platinotron A form of traveling-wave vacuum tube tor that cause a subaudible-tone modulation of a
used as an amplifier at ultra-high and microwave signal for use in restricted communications sys-
frequencies. There are two output connections. tems.
platinum Symbol, Pt. A precious metallic ele- plug A usually male quick-connect device that can
ment. Atomic number, 78. Atomic weight, be inserted into a JACK to make a circuit connec-
195.08. It is sometimes used for plating of relay tion, or be pulled out of the jack to break the con-
and switch contacts, and for certain parts of nection. See, for example, MALE PLUG, PHONE
vacuum tubes. PLUG, POWER PLUG, and POLARIZED POWER
platinum metals The rare metals IRIDIUM, OS- PLUG.
MIUM, PALLADIUM, PLATINUM, RHODIUM, and plug-and-jack connection A connection made by
RUTHENIUM. They do not react readily with inserting a PLUG into a JACK.
other elements. plug fuse A fuse provided with an Edison base for
platinum-tellurium thermocouple A thermocou- screwing into a socket.
ple using the junction between platinum and tel- pluggable Capable of being completely removed
lurium wires; it is used in thermocouple-type from the rest of the system without the need for
meters. removing any wiring. Pluggable components and
platter 1. One of the individual disks in a com- circuit boards simplify the servicing of electronic
puter HARD DISK drive. 2. The rotating turntable equipment.
in a PHONOGRAPH. plug-in See PLUG-IN COMPONENT and PLUG-IN
playback The reproduction of recorded material in UNIT.
audio-tape, audio-disc, video-tape, or video-disc plug-in capacitor A capacitor with pins or ferrules
systems. that can be quickly inserted into, or removed
playback computer system A personal computer from, a socket.
and associated peripherals, equipped for repro- plug-in coil A coil wound on a form having pins
ducing multimedia that has been recorded on that can be quickly inserted into, or removed
CD-ROM. from, a socket.
playback head In a magnetic recorder/reproducer, plug-in coil form An insulating form with base
the head that picks up the signal from the tape or pins that mate with socket terminals so that a
disc for reproduction. Also called read head and coil wound on the form can be quickly inserted
play head. into, or removed from, a circuit.
playback loss In disc recording, the difference (at a plug-in component A component or module, such
particular point on the disc) between the recorded as a transistor, capacitor, coil, lamp, etc., pro-
level and the reproduced level. vided with pins, clips, or contacts for easy inser-
player A semiconductor layer that is doped to pro- tion into, or removal from, a circuit. See, for
vide current carriers that are predominantly example, PLUG-IN CAPACITOR, PLUG-IN COIL,
holes. Compare N LAYER. PLUG-IN FUSE, PLUG-IN LAMP, PLUG-IN ME-
player A device or system that reproduces (plays TER, PLUG-IN RESISTOR, PLUG-IN TRANS-
back) data from a tape or disc, but cannot be FORMER, and PLUG-IN UNIT.
used to record data onto the tape or disc. plug-in fuse A cartridge fuse having a metal ferrule
play head See PLAYBACK HEAD. on each end for insertion into a matching clip for
playthrough The condition in which an amplifier easy installation and removal.
delivers a small output signal when the gain con-
trol is set to zero.
PLC Abbreviation of POWER-LINE COMMUNICA-
TION.
PLCC Abbreviation of PLASTIC-LEADED CHIP
CARRIER. plug-in fuse
plethysmograph A medical-electronic device that
allows the monitoring of the amount of blood in
different parts of the body. plug-in lamp A lamp with base pins for quick in-
PLL Abbreviation of PHASE-LOCKED LOOP. sertion into, or removal from, a socket.
PLM Abbreviation of pulse-length modulation (see plug-in meter A meter with pins or banana plugs for
PULSE-DURATION MODULATION). quick insertion into, or removal from, a circuit.
540 plug-in resistor • point defect


plug-in resistor A resistor with pins or ferrules for duplicated by merely touching two pieces of ma-
quick insertion into, or removal from, a socket. terial (one n-type and one p-type) together, how-
plug-in transformer A small transformer with pins ever smooth their mating faces.
for quick insertion into, or removal from, a pn-junction diode A diode consisting of the junc-
socket. tion between p-type and n-type regions in the
plug-in unit A unit, such as a tuned circuit, ampli- same wafer of semiconductor material.
fier, or meter, that has pins or contacts for easy PNM Abbreviation of PULSE-NUMBERS MODULA-
insertion into, or removal from, a larger piece of TION.
equipment. pnpn device See NPNP DEVICE.
plumber™s delight An antenna whose construc- pnp transistor A bipolar junction transistor in
tion, including that of the mast, is entirely of which the emitter and collector layers are p-type
metal rods or tubing, with no insulating parts. semiconductor material, and the base layer is
Short circuits and grounds are prevented by n-type semiconductor material. Compare NPN
making all attachments and joints at points that TRANSISTOR.
are at zero voltage, with respect to the standing- Po Symbol for POLONIUM.
wave pattern. Po Symbol for OUTPUT POWER or POWER OUT-
Plumbicon A television camera tube, similar to the PUT.
VIDICON, with a lead-oxide target. It is noted for POGO Abbreviation of polar orbiting geophysical
high sensitivity. The image lag time is shorter observatory.
than in the conventional vidicon. point 1. A dot indicating the place of separation
plumbing Collectively, the waveguides, tees, el- between the integral and fractional parts of a
bows, and similar pipelike devices and fixtures number (e.g., decimal point). Also called RADIX
used in microwave setups. POINT. 2. A precisely defined location in three-
plunger-type meter A meter in which an iron or dimensional space that has theoretically zero
steel plunger is pulled into a coil by the mag- length, zero width, and zero depth (e.g., focal
netism produced by a current flowing in the coil. point). 3. The place on a graph in any number of
The plunger is attached to a pointer that moves dimensions, at which two or more curves or coor-
over the scale. dinates intersect. 4. A set of operating conditions
plutonium Symbol, Pu. A radioactive metallic ele- for a component, device, or system (e.g., cutoff
ment that is artificially produced. Atomic num- point, operating point). 5. A defined condition at
ber, 94. Atomic weight, approximately 244. which some specific physical phenomenon occurs
PM 1. Abbreviation of PERMANENT MAGNET. (e.g., melting point).
2. Abbreviation of PULSE(D) MODULATOR. point charge An electric charge imagined to oc-
3. Abbreviation of post meridian. 4. Abbreviation cupy a single point in space; thus, it has neither
of PHASE MODULATION. area nor volume.
Pm 1. Symbol for PROMETHIUM. 2. Abbreviation point contact The point at which the sharply
of PETAMETER. pointed tip of a wire or rod conductor touches a
Pm Symbol for MAXIMUM POWER. second conductor (e.g., the contact between a
PME Abbreviation of photomagnetoelectric. “cat whisker” and a semiconductor wafer).
PMG Abbreviation of PERMANENT-MAGNET GEN- point-contact diode A semiconductor diode hav-
ERATOR. ing a fine wire (“cat whisker”), whose point is in
PMM Abbreviation of PERMANENT-MAGNET permanent contact with the surface of a wafer of
MAGNETIZER. semiconductor material, such as germanium or
PMOS Abbreviation of P-CHANNEL METAL-OXIDE silicon.
SEMICONDUCTOR. point-contact junction The pn junction electro-
PMU Abbreviation of portable memory unit. formed under the point at which the “cat
PN 1. Abbreviation of POLISH NOTATION. 2. Ab- whisker” touches the semiconductor wafer in a
breviation of POSITIVE-NEGATIVE (often lower- point-contact diode or transistor.
case). point-contact transistor A transistor having two
pn Abbreviation of POSITIVE-NEGATIVE. fine wires (“cat whiskers”) that serve as the emitter
pn boundary See PN JUNCTION. and collector electrodes. The pointed tips of the
pnip transistor A junction transistor having an in- wires are nearly in contact with (a few mils apart
trinsic layer between an n-type semiconductor from) the surface of a wafer of semiconductor ma-
base and one of the p-type semiconductor layers. terial, such as germanium. The semiconductor
pneumatic computer A computer that uses fluid serves as the base electrode. This device was a pre-
logic [i.e., one in which information is stored and decessor of the JUNCTION TRANSISTOR.
transferred by the flow of a fluid (gas or liquid) point counter A Geiger counter tube in which the
and pressure variations therein]. central electrode is a pointed, fine wire. Also see
pn junction The boundary between p-type and n- PROPORTIONAL COUNTER.
type semiconductor materials in a single block or point defect 1. In a semiconductor substance or
wafer of the materials. The junction cannot be piezoelectric crystal, the absence of an atom from
541
point defect • polarization


its place in the lattice structure. 2. The presence polar coordinates The magnitude and direction of
of an extra atom in the lattice structure. a vector in a defined plane, listed as a radius
point effect The tendency of an electrical dis- (magnitude) in combination with an angle (direc-
charge to occur more readily at a sharp point tion) between the vector and the polar axis.
than at a blunt surface (as of an electrode).
pointer A pointed blade, stiff wire, or inscribed line
(r,θ)
on a transparent blade; it moves over a scale to
indicate a setting or the value of a quantity. Also
called NEEDLE.
pointer-type meter An analog meter in which a
θ
pointer moves over a calibrated scale.
point impedance 1. The impedance observed at a
given point in a circuit. 2. In a transmission line,
the intensity of the electric field divided by the in-
tensity of the magnetic field at a given point.
points of saturation For a magnetic core, satura-
tion as evidenced by a leveling-off of the positive r
Origin: r = 0
and negative halves of the magnetization curve. 0 2 4 6 8
point source A source from which electromagnetic
radiation emanates, and that appears as a geo- polar coordinates
metric point from a great distance.
point mode Descriptive of cathode-ray-tube dis-
play operation (in a computer system), in which polarimeter An instrument for measuring the
data is portrayed as plotted dots. amount of polarized light in a ray that is only par-
point-to-point communication Communication tially polarized.
between two stations whose location can be pre- polariscope An instrument used in the observation
cisely specified. or testing of materials under POLARIZED LIGHT.
point-to-point motion A method of robot arm polarity 1. The condition of being electrically posi-
movement in which the device can attain only tive or negative. 2. The condition of being mag-
certain positions. The coordinates of each stop- netically north or south. 3. The orientation of the
ping point are stored in the robot controller (com- positive and negative poles in a battery or power
puter) memory. supply relative to a circuit. 4. The orientation of a
point-to-point station A radio station that pro- magnetic field, relative to the surrounding envi-
vides POINT-TO-POINT COMMUNICATION. ronment.
point-to-point wiring A method of wiring an elec- polarity blanking See POLARITY INHIBIT.
tronic circuit in which wires are run directly be- polarity inhibit In some instruments, especially
tween the terminals or components, usually by those having automatic polarity, the automatic
the shortest practicable route. It is used mainly blanking of the polarity sign.
in high-voltage circuits, such as power amplifiers. polarity-sensitive relay A direct-current relay ac-
Compare CABLED WIRING. tuated only when coil current flows in one direc-
poise The cgs unit of absolute viscosity; 1 poise is tion. One of the simplest versions is a relay
the absolute viscosity of a fluid that requires a having a semiconductor diode connected in series
shearing force of 1 dyne to move a 1-sq-cm area with its coil.
of one of two parallel layers of the fluid (1 cm polarity shifter A potentiometer connected to two
apart) with a velocity of 1 cm per second, with re- direct-current sources so that a pair of output
spect to the other layer. The comparable SI unit is terminals has plus and minus polarities at one
the newton-second per meter squared (N • s/m2); extreme of potentiometer adjustment, and minus
1 poise = 0.1 N • s/m2. and plus at the other extreme. At the center of the
polar axis 1. In a crystal, the axis of rotation not range, the output voltage is zero.
perpendicular to a reflection plane. 2. The polarity switch A double-pole, double-throw
straight line connecting epicenters of electric, switch connected between a pair of direct-current
magnetic, or gravitational poles in a system. input terminals so that the polarity of a pair of
3. The axis about which the earth or another output terminals can be interchanged.
planet rotates. polarization 1. In a radio wave, the orientation of
polar coordinate conversion See POLAR COOR- the electric lines of flux, with respect to the sur-
DINATE TRANSFORMATION. rounding environment (e.g., horizontal polariza-
polar-coordinate geometry A two-dimensional tion and vertical polarization). 2. The disabling of
system for movement of industrial-robot arms. It a battery cell by the formation of insulating gas
is based on a system of POLAR COORDINATES, on one of the plates. 3. The condition in which
in which a radius and a direction angle are as- transverse waves of light are confined to a specific
signed to each point in the working plane. (e.g., horizontal or vertical) plane.
542 polarization diversity • polarizing filter


polarization diversity A form of reception in polarized plug A plug that can be inserted into a
which two separate receivers, tuned to the same socket or receptacle in only one way to ensure
signal, are connected to independent antennas. safe and foolproof operation.
One antenna is vertically polarized and the other
is horizontally polarized. The result is a reduction
in fading caused by ionospheric effects on the po-
larization of the incoming signal.
Larger pin
is ground
Both antennas
at least »/2 apart
Vertical
antenna
Horizontal antenna


polarized plug

polarized power plug A polarized plug for connec-
RX
tion of equipment to an alternating-current utility
power source.
polarization diversity polarized reactor A saturable reactor in which the
lines of flux produced in the three-leg core by the
coils on the two outer legs are added in the center
polarization error In the operation of a loop an- leg. Consequently, the flux can reinforce or op-
tenna (e.g., that of a direction finder), null error pose the controlling current in the coil on the
caused by waves arriving with polarization oppo- center leg, depending on the direction of the cur-
site that of the loop (thus, vertically polarized rent. Compare NONPOLARIZED REACTOR.
waves at a horizontal-plane loop, and vice versa). polarized receptacle A receptacle constructed so
polarization fading In radio reception, a form of that it can receive a plug in only one way, thus
fading that results from changes in the polariza- preventing incorrect connections.
tion of the arriving signal with respect to the re-
ceiving antenna. When the polarization of the
arriving signal coincides with that of the receiving
Larger pin
antenna, the received signal strength is maxi- socket is
mum. When the received-signal polarization is at ground
right angles to the receiving antenna, the signal
strength is minimum.
polarization modulation A method of impressing
information on a signal by changing the polariza-
tion of the radiated electromagnetic field.
polarization selectivity For a photoemissive sur-
face, the condition in which the ratio of photocur-
rents for two different angles of plane polarization
of the light incident to the surface differs from the
ratio of the corresponding amounts of light
absorbed by the surface. Also see PHOTO- polarized receptacle
EMISSION; PHOTOEMISSIVE MATERIAL; and
POLARIZATION, 3.
polarized relay A relay actuated by one polarity of
polarized capacitor A conventional electrolytic ca-
direct current, or by one particular phase of al-
pacitor, so called because one particular terminal
ternating current. Such a relay sometimes con-
must be connected to the more positive of the two
tains an armature-centering permanent magnet.
connection points. Compare NONPOLARIZED
polarized socket See POLARIZED RECEPTACLE.
ELECTROLYTIC CAPACITOR.
polarized X rays X-ray waves whose electric lines
polarized light Visible light waves whose electric
of flux are more or less oriented in a specific
lines of flux are confined more or less to a single
plane, as when they are scattered by carbon
plane. This effect can be obtained via filtering; it
blocks. See, for illustration, POLARIZATION, 3
also occurs naturally under certain conditions.
and POLARIZED LIGHT.
Scattered sunlight is polarized to some extent by
polarizing filter A light filter that consists essen-
the atmosphere. Light is polarized to some extent
tially of microscopic heraphathite plastic plate.
when it reflects from a plane surface. Also see PO-
The plate can be rotated to cause light passing
LARIZING FILTER.
543
polarizing filter • polygraph


through it to be polarized in any particular plane pole shoe In an electric motor, the section of the
between horizontal and vertical, depending on field pole nearest the armature.
the degree of rotation. Also see POLARIZED poles of impedance For a reactive network, the
LIGHT. frequencies at which the impedance is infinite.
polarography In chemistry, a form of qualitative or Compare ZEROS OF IMPEDANCE.
quantitative analysis utilizing IE curves obtained poles of network function The values at which a
when the voltage is gradually increased across a network function is infinite. Compare ZEROS OF
solution in ELECTROLYSIS. NETWORK FUNCTION.
polar orbit An orbit that carries a satellite over the poles of transfer function The frequencies at
geographic polar regions of the earth. This type of which a transfer function becomes infinite. Com-
orbit is oriented at, or nearly at, 90 degrees with pare ZEROS OF TRANSFER FUNCTION.
respect to the equator, and can have a period police robot A proposed robotic machine, either
ranging from about 90 minutes to several weeks autonomous or remotely controlled (teleoper-
or even months. Low-earth-orbit (LEO) satellites ated), that would be used to assist in law enforce-
generally have such orbits. ment, particularly in dangerous operations.
poling The deliberate adjustment of electromag-
netic-field polarity.
Satellite Polish notation In Boolean algebra, a form of no-
orbit tation wherein the variables in a statement are
preceded by the operators.
polling In data transmission, a technique in which
channels being shared by more than one termi-
nal are tested to find one over which data is
North coming in, or to ascertain which is free for
pole
transmission.
polonium Symbol, Po. A radioactive metallic ele-
ment. Atomic number, 84. Atomic weight, ap-
Earth
proximately 209.
polychromatic radiation 1. Visible-light radiation
having more than one wavelength; in particular,
covering a broad range of wavelengths. 2. Elec-
tromagnetic radiation over a broad band of wave-
lengths.
polycrystalline material A substance, such as a
semiconductor, of which even a very small
sample consists of a number of separate cry-
stals bound tightly together. Compare SINGLE-
CRYSTAL MATERIAL.
Equator
polydirectional microphone See OMNIDIREC-
TIONAL MICROPHONE.
polyelectrolyte An ELECTROLYTE having high
molecular weight.
polyester A resin made by reacting a dihydroxy al-
polar orbit
cohol with a dibasic acid.
polyester backing A polyester tape on the surface
of which iron oxide is deposited to yield a mag-
polar-orbiting satellite Any satellite in a POLAR
netic recording tape.
ORBIT.
polyethylene A plastic insulating material. Dielec-
polar planimeter See PLANIMETER.
tric constant, 2.2. Dielectric strength, 585 V/mil.
polar relay See POLARIZED RELAY.
polyethylene disc A phonograph disc made of
polar response The horizontal-plane directional
polyethylene.
response of an antenna or other transducer.
polygonal coil A coil wound on a form having a
pole 1. An extremity or terminus that possesses
polygonal, rather than circular cross section.
POLARITY. Examples: magnetic pole and electric
Some polygonal forms have as many as 12 sides
pole. 2. The movable member of a switch. 3. One
in cross section.
of the frequencies at which a transfer function
polygraph An instrument for measuring and
becomes infinite.
recording electrical signals proportional to blood
pole face The smooth end surface of a pole piece.
pressure, skin resistance, breathing rate, and
pole piece 1. A section of specially shaped iron or
other reactions that vary under emotional stress.
steel that is attached to a magnetic core. 2. Half
Also called LIE DETECTOR. Compare PATHOME-
of a two-piece magnetic core that terminates in a
TER.
pole.
544 polymer • position


polymer A compound that is the product of poly- polypropylene A plastic material commonly used
merization, resulting from the chemical union of as an electrical insulator. Dielectric constant,
monomers. Also see POLYMERIZE. 2.0. Dielectric strength, 600 V/mil.
polymerize To unite monomers or polymers of the polyrod antenna A tapered dielectric antenna,
same kind to form a molecule having a higher usually made of polystyrene, for directional mi-
molecular weight. crowave transmission.
polyphase In alternating-current circuits, pertain- polysilicon A polycrystalline form of silicon (see
ing to the existence or generation of two or more POLYCRYSTALLINE MATERIAL).
specific electrical phases. Compare SINGLE polystyrene A clear, colorless thermosetting-type
PHASE. plastic. It is widely used as an insulating material
polyphase antenna An antenna consisting of two in radio-frequency circuits and, to some extent,
dipole radiators mounted perpendicular to each as a dielectric film in fixed capacitors. Dielectric
other at their midpoint and excited 90 degrees constant, 2.4 to 2.9. Dielectric strength, 20 to 28
out of phase. The radiation pattern is approxi- kV/mm.
mately circular in the plane of the elements. Also polystyrene capacitor A high-Q capacitor in
called TURNSTILE ANTENNA. which the dielectric film is polystyrene.
polyvinyl chloride Abbreviation, PVC. A plastic
insulating material. Dielectric constant, 3.6 to
4.0. Dielectric strength, 800 V/mil.
pool cathode In an industrial electron tube, a
90° Phase shift
cathode consisting of a pool of mercury.
pool-cathode tube An industrial electron tube us-
ing a pool cathode. Examples: excitron, ignitron,
and mercury-arc rectifier.
popcorn noise A temperature-dependent, random-
shot electrical noise. In a radio receiver or audio
circuit, this noise resembles the sound of popping
corn. It occurs in some operational amplifiers.
polyphase antenna
population In statistical analysis, the total group
of items, quantities, or values under considera-
polyphase generator 1. A dynamo-type generator tion. Sometimes called universe.
of polyphase power (two-phase, three-phase, porcelain A hard, white, usually glazed ceramic
etc.). 2. See POLYPHASE OSCILLATOR. used as a dielectric and insulant. Dielectric con-
polyphase oscillator An oscillator circuit that gen- stant, 6 to 7.5. Dielectric strength, 40 to 100
erates polyphase alternating current. The circuit V/mil. Also called china.
contains separate oscillators for each phase. A porcelain capacitor A ceramic-dielectric capacitor
three-phase circuit, for example, has three sym- in which the dielectric is composed of porcelain or
metrical oscillators with matched inductance and a related substance.
capacitance values. porcelain insulator An electric insulator fabri-
polyphase power 1. The total dissipated power in cated from porcelain.
a polyphase alternating-current circuit. 2. Poly- porch See BACK PORCH and FRONT PORCH.
phase alternating current provided for utility pur- port 1. In a circuit, device, or system, a point at
poses. which energy or signals can be introduced or ex-
polyphase rectifier A rectifier of polyphase alter- tracted in a particular manner (e.g., two-port cir-
nating current generally obtained from a three- culator and I/O port). 2. An aperture in a
phase power line through a transformer. The loudspeaker enclosure.
several common circuits usually contain a diode portable-mobile station See MOBILE STATION.
for each phase. Such rectifiers offer the advan- portable station A communications station that
tage of higher ripple frequency than is obtainable can be carried from one location to another. A
by single-phase operation. For a three-phase rec- portable station differs from a mobile station in
tifier, for example, the ripple frequency is three that a portable station does not usually operate
times the line frequency; for a six-phase rectifier, while in motion, whereas a mobile station does.
it is six times the line frequency. ported reflex enclosure A loudspeaker cabinet
polyphase system An alternating-current circuit with openings that facilitate bass (low-frequency)
in which voltages or currents are normally out of sound reproduction.
phase with each other by some fixed amount. Fa- pos 1. Abbreviation of POSITIVE. 2. Abbreviation
miliar types are two-phase and three-phase. of POSITION.
polyphase transformer An alternating-current position 1. The location of a point or object with re-
transformer specifically designed for use in cir- spect to one or more (usually fixed) references.
cuits that have two or more simultaneous current 2. The setting of an adjustable device, such as a
phases. potentiometer, rotary switch, or variable capacitor.
545
positional notation • positive ghost


positional notation A method of representing positive conductor The conductor or line con-
numbers in which the number is indicated by the nected to the positive terminal of a current,
positions and value of the component digits. The voltage, or power source. Compare NEGATIVE
decimal number system belongs in this category CONDUCTOR.
(e.g., the decimal number 1284.67 is equal to 1 — positive electricity See POSITIVE CHARGE and
103 + 2 — 102 + 8 — 101 + 4 — 100 + 6 — 10“1 + 7 — POSITIVE ELECTRIFICATION.
10“2). positive electrification Electrification character-
positional number system See POSITIONAL NO- ized by a deficiency of electrons. For example,
TATION. when a glass rod is rubbed with a silk cloth, the
positional representation See POSITIONAL NO- rod becomes positively charged because electrons
TATION. are rubbed off the glass onto the silk. Similarly,
position-control potentiometers In an oscillo- when an atom loses an electron, it becomes elec-
scope, potentiometers used to control the voltage trified positively because it has a deficiency of elec-
applied to the horizontal and vertical deflecting trons. Compare NEGATIVE ELECTRIFICATION.
plates to position the spot on the screen. Also see positive electrode 1. An electrode connected to
CENTERING CONTROL. the positive terminal of a current, voltage, or
position controls See POSITION-CONTROL PO- power source. 2. The positive terminal of a cur-
TENTIOMETERS. rent, voltage, or power source, such as a battery
position feedback In a servo or other control sys- or generator.
tem, feedback current, or voltage that is propor- positive electron See POSITRON.
tional to the position assumed by a member. positive element See POSITIVE ELECTRODE, 1.
position fixing The determination of a position positive error of measurement An error of mea-
from the intersection on a map of two lines derived surement in which the difference between a mea-
from the direction-finding pickups of two trans- sured value and the true or most probable value
mitting stations. Also see DIRECTION FINDER. is positive. Compare NEGATIVE ERROR OF MEA-
position indicator In a tape recorder, a counter SUREMENT.
whose numbered wheels revolve when the reels positive exponent A positive superscript indicat-
do, thus aiding in locating a desired spot on the ing that a number (x) is to be raised to the posi-
tape. Also called tape counter. tive nth power. Thus, in the expression xn, the
positioning circuit The circuit associated with a value of n is greater than zero. Compare NEGA-
horizontal or vertical centering control (see CEN- TIVE EXPONENT.
TERING CONTROL). positive feedback Feedback that is in phase with
position sensing 1. In robotics and navigation an input signal. Also called REGENERATION and
systems, a method of determining location, rela- REGENERATIVE FEEDBACK. Compare NEGA-
tive to the surrounding environment. 2. Any TIVE FEEDBACK.
method via which a robot can accurately deter-
mine the location(s) of its end effector(s).
+Vcc
position sensor An electronic circuit that detects
Feedback
physical displacement, and transmits a signal
resistor
proportional to the displacement.
positioning control See CENTERING CONTROL.
positive 1. Possessing positive (plus) direct-
+
current electrical polarity. 2. Pertaining to real
numbers greater than zero. 3. A photographic
Input
image whose shadings are the same as those in
Output
the scene.

positive angle 1. In a system of rectangular coor-
dinates, an angle in the first or second quadrant.
2. In rectangular coordinates, an angle measured
counterclockwise from the positive x-axis.
positive feedback
Compare NEGATIVE ANGLE.
positive bias A positive voltage or current applied
continuously to an electrode of a device (as to a positive function A function having the positive
transistor base) to maintain the device™s operat- sign. In the rectangular coordinate system, the
ing point. Compare NEGATIVE BIAS. trigonometric sine function is positive in the first
positive bus See POSITIVE CONDUCTOR. and second quadrants, the cosine in the first and
positive charge An electrical charge characterized fourth, and the tangent in the first and third.
by having relatively fewer electrons than a nega- Compare NEGATIVE FUNCTION.
tive charge. Also see CHARGE, 1; ELECTRIC positive ghost In a television picture, a ghost with
CHARGE; and UNIT ELECTROSTATIC CHARGE. positive shading (see POSITIVE, 3). Also see
Compare NEGATIVE CHARGE. GHOST.
546 positive-going • positive resistor


positive-going Pertaining to a signal whose value positive number A real number, whose value is
is changing in a positive direction. This is not re- greater than zero. Compare NEGATIVE NUMBER.
stricted to signals of actual positive polarity; a positive peak The maximum amplitude of a posi-
decreasing negative voltage, for example, is tive half-cycle or positive pulse.
positive-going as it falls in the direction of zero” positive-peak clipper A peak clipper that levels off
even if it never crosses the zero line. the positive half-cycle of an alternating-current
positive grid In an electron tube, a control grid wave to a predetermined level.
whose bias or signal voltage is positive, with re- positive-peak modulation Amplitude modulation
spect to the cathode. of the positive peaks of a carrier wave.
positive-grid oscillator A microwave oscillator cir- positive-peak voltmeter An electronic voltmeter
cuit in which the control grid of a triode tube is for measuring the amplitude of the positive peak
operated at a positive direct-current potential, of an alternating-current (ac) wave. In its sim-
and the plate at a negative potential. Electrons plest form, it consists essentially of a direct-
move back and forth between cathode and plate, current (dc) microammeter with a diode oriented
through the grid, and thus give rise to an oscillat- to pass the positive half-cycle. A series capacitor
ing current. in the circuit is charged to approximately the
positive ground A direct-current electrical system peak value of the applied ac voltage. Compare
in which the positive power-supply terminal is NEGATIVE-PEAK VOLTMETER.




Y
connected to the common ground. It is not gener-
ally used in North America.




FL
Discharge
positive half-alternation See POSITIVE HALF-
switch
CYCLE.
+
positive half-cycle That half of an alternating-
+
current cycle in which the current or voltage in- Input
AM
+
creases from zero to maximum positive and re- ’
turns to zero. V
positive image 1. A picture in which the blacks,
whites, and grays correspond to those in the actual ’
scene (see POSITIVE, 3). 2. A normal television pic-
TE

ture (i.e., one that has the shading described in 1).
positive ion An atom that has a deficiency of elec-
trons and, consequently, exhibits a net positive positive-peak voltmeter
charge. Also called CATION.
positive lead See POSITIVE CONDUCTOR.
positive light modulation In television transmis- positive phase-sequence relay A phase-sequence
sion, the condition in which transmitted power relay that responds to the positive phase se-
increases as the light intensity increases. Com- quence in a polyphase circuit. Compare NEGA-
pare NEGATIVE LIGHT MODULATION. TIVE PHASE-SEQUENCE RELAY.
positive line See POSITIVE CONDUCTOR. positive picture modulation See POSITIVE MOD-
positive logic 1. Binary logic in which a low posi- ULATION.
tive state represents logic 0, and a high positive positive picture phase In a television signal, the
state represents logic 1. 2. Binary logic in which swinging of the picture-signal voltage from zero to
a high negative state represents logic 0, and a low positive, in response to an increase in brightness
negative state represents logic 1. Compare NEG- in the scene. Compare NEGATIVE PICTURE
ATIVE LOGIC. PHASE.
positive magnetostriction A form of MAGNE- positive plate 1. The positive member of an elec-
TOSTRICTION in which the physical size of a trochemical cell or battery. Electrons flow to this
substance is directly proportional to the intensity plate from the negative plate, through the exter-
of the surrounding magnetic field. nal circuit. 2. A vacuum-tube plate that is biased
positive measurement error See POSITIVE ER- positively, as in a conventional tube circuit.
ROR OF MEASUREMENT. positive pole See POSITIVE ELECTRODE, 1, 2.
positive modulation In amplitude-modulated positive potential 1. The voltage at a positive elec-
television transmission, the increase in transmit- trode (with respect to the negative electrode).
ted power when the brightness of the scene in- 2. Voltage greater than that at ground as a refer-
creases. Compare NEGATIVE MODULATION. ence.
positive modulation factor For an amplitude- positive power See POSITIVE EXPONENT.
modulated wave having unequal positive and positive resistance Ohmic resistance (see OHMIC
negative peaks, a ratio expressing the maximum RESPONSE). Compare NEGATIVE RESISTANCE.
positive deviation (increase) from the average positive resistor A resistor whose value does not
value of the envelope. Compare NEGATIVE MOD- change with current or voltage changes. Compare
ULATION FACTOR. NEGATIVE RESISTOR.




Team-Fly®
547
positive temperature coefficient • potential energy


positive temperature coefficient Abbreviation, coils are connected so that they can be replaced
PTC. A number expressing the amount by which a by shorting connectors.
quantity (such as the value of a component) in- pot 1. See POTENTIOMETER. 2. See DASHPOT.
creases when temperature is increased. The coef- 3. Abbreviation of POTENTIAL. 4. To encapsulate a
ficient is stated as a percentage of the rated value circuit in a potting compound, such as epoxy resin.
per degree, or in parts per million per degree. potassium Symbol, K. A metallic element of the al-
Compare NEGATIVE TEMPERATURE COEFFI- kali-metal group. Atomic number, 19. Atomic
CIENT and ZERO TEMPERATURE COEFFICIENT. weight, 39.098.
positive transmission In facsimile or television, a potassium chloride Formula, KCl. A compound
form of amplitude modulation in which the pic- used as a phosphor coating on the screen of a
ture brightness is directly proportional to the sig- nearly permanent-persistence cathode-ray tube.
nal strength at any given instant of time. The fluorescence is magenta or white, as is the
positive valence The valence of a positive ion. phosphorescence.
positron A positively charged particle having the potassium cyanide Formula, KCN. A highly toxic
same mass as that of the electron, and the same salt that is an electrolyte in some forms of elec-
magnitude of electric charge, but positive (instead troplating.
of negative). Sometimes called positive electron. potassium dihydrogen phosphate Abbreviation,
post See BINDING POST. KDP. An inorganic ferroelectric material.
post- Prefix meaning “following,” “subsequent to,” pot core A magnetic core for a coil, made of ferrite
or “behind.” or of powdered iron, consisting of a central rod, a
post-accelerating electrode In a cathode-ray surrounding potlike enclosure, and a lid. The rod
tube, the high-voltage electrode that produces passes through the center of the coil, and the pot
POST-DEFLECTION ACCELERATION of the elec- and lid completely enclose the coil. This arrange-
tron beam. Also called INTENSIFIER ELEC- ment provides a completely closed magnetic cir-
TRODE. cuit and coil shield.
postacceleration See POST-DEFLECTION ACCEL-
ERATION.
post-alloy-diffused transistor Abbreviation,
PADT. A transistor in which electrodes are dif-
Slot for coil
fused into the semiconductor wafer after other
electrodes have been alloyed.
post-conversion bandwidth The bandwidth of a
signal after it has been converted from one fre-
Slot for
quency to another.
coil
post-deflection accelerating electrode See
POST-ACCELERATING ELECTRODE.
post-deflection acceleration In a cathode-ray
tube, the intensification of the electron beam
following beam deflection. Also see POST- Clamping
DEFLECTION CRT. bolt
post-deflection CRT An oscilloscope tube pro-
vided with a high-voltage intensifier electrode in pot core
the form of a ring encircling the inside flare of the
tube, between the deflecting plates and the
screen. The deflected electron beam is acceler- potential See ELECTROMOTIVE FORCE.
ated by this electrode. This arrangement allows potential barrier The electric field produced on
the beam to be deflected at low velocity and high each side of a semiconductor junction by minor-
sensitivity, then to be accelerated for a brighter ity carriers (i.e., by holes in the n-layer and elec-
image. trons in the p-layer) that face each other across
post edit The editing of data in a computer output. the junction, but cannot diffuse across the junc-
postemphasis See DEEMPHASIS. tion and recombine.
post-equalization 1. In sound recording and re- potential coil The shunt coil in a conventional
production, equalization during playback. Com- wattmeter.
pare PREEQUALIZATION. 2. See DEEMPHASIS. potential difference See ELECTROMOTIVE
postmortem An investigation into the cause of FORCE and VOLTAGE.
failure of a circuit, device, or system. potential divider See VOLTAGE DIVIDER.
postmortem dump At the end of a computer pro- potential drop 1. A voltage difference between two
gram run, a dump to supply information for de- points in a circuit. 2. The voltage across a resis-
bugging purposes. tor in a direct-current circuit.
post office box A type of wheatstone bridge that potential energy Energy resulting from the posi-
contains resistance coils in a special box. The tion of a body or particle (e.g., the energy stored
548 potential energy • power amplifier


in something lifted against gravity and held in its potting material A substance, such as a resin or
new position) or from the position of charges (e.g., wax, used for potting electronic gear. Also called
the energy stored in a charged capacitor). Com- potting compound.
pare KINETIC ENERGY. pound 1. Abbreviations, lb, p. A unit of weight
potential gradient See VOLTAGE GRADIENT. equal to 16 avoirdupois ounces. 2. Abbreviation,
potential profile A rectangular-coordinate display lbf. A unit of force approximately equal to 4.448
of the VOLTAGE GRADIENT across a body (e.g., newtons. 3. Abbreviation, lbm. A unit of mass ap-
the cross section of a transistor). proximately equal to 0.4536 kilogram.
potential transformer A small step-up trans- poundal A unit of force equal to approximately
former for increasing the range of an alternating- 13825.5 dynes or 0.138255 newton. One poundal
current voltmeter. is the force that, when acting for one second, will
potentiometer 1. A variable resistor used as a volt- impart a speed of one foot per second to a one-
age divider. The input voltage is applied across the pound mass.
entire resistance element and the output voltage pound-foot Abbreviation, lb-ft. A unit of torque
is taken from the wiper, relative to one end of the equal to the product of a force of one pound and
element. One end is usually grounded (at zero po- a moment arm of one foot. Compare OUNCE-
tential). 2. A null device whose operation is based INCH.
on a variable resistor, and is used for precise volt- pounds per square inch absolute Abbreviation,
age measurements. The unknown voltage is ap- psia. Absolute pressure (i.e., the sum of atmo-
plied to the input of a variable resistor whose spheric pressure and the pressure indicated by a
settings are known with great accuracy; the resis- gauge). Compare POUNDS PER SQUARE INCH
tance is adjusted for an output voltage that ex- GAUGE.
actly equals the voltage of a standard cell (as pounds per square inch gauge Abbreviation,
indicated by a null between the two voltages). The PSIG. The value of pressure indicated by a gauge,
unknown voltage is then determined from the re- without correction for atmospheric pressure.
sistance and the standard-cell voltage. Compare POUNDS PER SQUARE INCH ABSO-
potentiometer noise In a current-carrying poten- LUTE.
tiometer, electrical noise generated when the powdered-iron core A magnetic core consisting of
wiper blade rubs against the resistance element, minute particles of iron, each coated with a film
or by contact between the blade and element. to insulate it from others, molded into a solid
potentiometric recorder A type of graphic mass. Because of its low eddy-current loss, this
recorder. It consists essentially of a resistance- type of core is usable in radio-frequency trans-
calibrated potentiometer, a standard cell, and a formers and coils, where it increases the induc-
galvanometer. When an unknown voltage (Ex) is tance of the winding.
applied to the input terminals of the potentiome- power 1. Symbol, P. Unit, watt. The rate of doing
ter and the potentiometer is set for null, Ex = Es work, or producing or transmitting energy. In
(R2/R1), where Es is the voltage of the standard direct-current circuits, and in alternating-current
cell, R1 is the input resistance of the potentiome- circuits containing no reactance, power is the
ter, and R2 is the output resistance of the poten- product of the root-mean-square current and
tiometer. voltage. See, for example, AC POWER, APPARENT
Potier diagram An illustration of the phase rela- POWER, DC POWER, KILOVOLT-AMPERE,
tionship between current and voltage in an alter- POWER FACTOR, REACTIVE KILOVOLT-
nating-current circuit that contains reactance. AMPERE, REACTIVE VOLT-AMPERE, TRUE
POTS Acronym for plain old telephone service, POWER, VOLT-AMPERE, WATT, and WATTLESS
meaning basic service without optional features POWER. 2. The product obtained by multiplying
(such as call waiting, conference calling, call for- a quantity x by itself n times, written xn. For ex-
ample, 24 = 2 — 2 — 2 — 2 = 8; here, 8 is the fourth
warding, etc.).
potted circuit A circuit embedded in plastic or power of 2. Compare ROOT, 1. 3. The exponent in
wax to protect it against the environment, and/or an expression, as defined in 2.
to minimize the effects of physical vibration (see power amplification 1. The amplification of a sig-
POTTING). nal having a certain power (wattage) to produce a
potted component An electronic part embedded signal having greater power. 2. The signal power
in a suitable plastic or wax to protect it against increase, expressed as a ratio or as a figure in
the environment, and/or to minimize the effects decibels, resulting from the process defined in 1.
of physical vibration (see POTTING). Also called POWER GAIN.
potting A process of embedding a component or power amplification ratio See POWER AMPLIFI-
circuit in a solid mass of plastic or wax held in a CATION, 2 and POWER GAIN.
container. The process is similar to encapsula- power amplifier An amplifier that delivers useful
tion, except that in potting, the container (enve- amounts of power to a load, such as one or more
lope) remains as part of the assembly. Compare speakers. Compare CURRENT AMPLIFIER and
ENCAPSULATION. VOLTAGE AMPLIFIER.
549
power-amplifier device • power grid


power dissipation Abbreviation, PD. The power
consumed by a device during normal operation.
This power is not available in the electrical output
of the device. An example is the direct-current
power dissipated in the collector circuit of a high-
+ Output fidelity audio amplifier.
Input
power divider A circuit that distributes power, in a
predetermined manner, among various loads.
power drain The amount of power drawn by a de-
vice. It can be operating power or standby power.
power dump See DUMP, 2.
power equations Variations of the basic power
equation: P = EI = E2/R = I2R, where P is the
power amplifier
power in watts, E is the voltage in volts, I is the
current in amperes, and R is the resistance in
ohms.
power factor Abbreviation, PF. In an alternating-
power-amplifier device A high-current tube or
current circuit, the ratio (expressed either as a
transistor designed especially for high power
decimal or a percentage) of true power (power ac-
output. Such a device does not always provide
tually consumed) to apparent power (simple
significant voltage amplification, but always pro-
product of voltage and current). The power factor
vides power amplification. Compare VOLTAGE-
is equal to the cosine of the phase angle. Also see
AMPLIFIER DEVICE.
AC POWER.
power at peak torque Symbol, Pp. For a torque
power-factor balance In a capacitance bridge, a
motor, the input power in watts needed for peak
separate null adjustment for the internal resis-
torque at stall at a winding temperature of 25 de-
tance component of a capacitor under measure-
grees Celsius.
ment. The dial of the variable component for this
power attenuation 1. A reduction of power level.
adjustment reads directly in percent power factor
2. See POWER LOSS.
in some bridges.
power bandwidth For a high-fidelity audio ampli-
power-factor correction To raise the power factor
fier, the difference between the maximum and
of an inductive circuit by inserting a parallel ca-
minimum frequencies at which the amplifier can
pacitance. In power circuits, this affords im-
produce at least 50 percent of its maximum
proved economy of operation because the current
power output, with less than a certain amount of
drain is brought more in line with that of a resis-
total harmonic distortion (usually 10 percent).
tive circuit.
power blackout A situation in which all electric
power-factor meter An instrument that gives di-
power is lost to utility subscribers in a defined re-
rect readings of power factor (lead or lag). One
gion.
such meter uses a dynamometer-type movement
power consumption 1. For a direct-current de-
(see ELECTRODYNAMOMETER) in which the ro-
vice, the normal operating voltage multiplied by
tating element consists of two coils fastened to-
the normal drawn current. 2. For an alternating-
gether at right angles.
current circuit, the root-mean-square voltage
power-factor regulator A device that regulates the
multiplied by the root-mean-square current.
power factor of an alternating-current line.
power control The adjustment of the output volt-
power-factor relay An alternating-current relay
age of a power supply, usually by means of a vari-
actuated by a rise or fall in power factor, with re-
able autotransformer, silicon-controlled rectifier,
spect to a predetermined value.
thyratron, or similar device.
power frequency 1. See POWER-LINE FRE-
power cutoff frequency Symbol, fco. The frequency
QUENCY. 2. The frequency of an alternating-
at which the power gain of a transistor drops 3 dB
current generator. 3. The output frequency of a
below its low-frequency value.
power inverter (see INVERTER, 1).
power derating For a temperature higher than the
power-frequency meter An instrument for mea-
specified ambient temperature, a deliberate re-
suring power-line frequency. It can use elec-
duction of the power dissipated by a component
tromechanical devices, or can directly count the
or device. This is done to prevent failure of the
number of alternations per second.
component or device. Also see DERATING, DER-
power gain Abbreviations, PG or PGdB. The extent
ATING CURVE, and DERATING FACTOR.
to which power is increased by a power amplifier.
power difference An expression of the power lost
It can be expressed as the ratio of power output to
in a circuit when power is absorbed by a dielectric
power input as PG = Po/Pi, or in decibels as
material.
PGdB = 10 log10(Po/Pi).
power diode A heavy-duty diode that is usually
power grid An aggregation of power-generating
used in power-supply service. Also called rectifier
stations, transmission lines, and associated
diode.
550 power grid • power surge


equipment, usually extending over hundreds of power-loss factor Symbol, Fp. In interstage cou-
miles and embracing several communities, so op- pling, the ratio of available power (with the cou-
erated that individual members can deliver power pling network in place) to the available power
to the system or draw power from it, according to when the network is disconnected.
local demand. power meter See WATTMETER.
power ground The power-supply ground for a cir- power modulation factor In amplitude modulation,
cuit or system. the ratio of the peak power to the average power.
power-handling capacity 1. The amount of power power oscillator A heavy-duty oscillator delivering
that a device can dissipate, either continuously or useful power output.
intermittently, without suffering damage. 2. The power output See OUTPUT POWER.
maximum input power that can be tolerated by an power-output meter See OUTPUT POWER ME-
amplifier transistor or tube without overheating. TER.
power hyperbola For a semiconductor device or power pack An external power-line-operated unit
vacuum tube, a curve plotted from the device™s supplying alternating or direct current for the op-
current and voltage values, which provide the eration of electronic equipment.
power value when multiplied (e.g., a 2-watt curve power pentode A heavy-duty pentode vacuum tube
for the direct-current collector input of a power designed to deliver relatively high output power.
transistor). power plug A plug for insertion into a power-line
power input See INPUT POWER. outlet.
power-input control The adjustment of the output power programmer A device that adjusts radar
of a power supply by varying the alternating- output power, in accordance with the target dis-
current input to the power transformer. Usually, tance.
a variable autotransformer is operated ahead of power rating 1. The specified power required by an
the power transformer. See, for example, equipment for normal operation. 2. The specified
VARIABLE TRANSFORMER and VARIAC. power output of a generator or amplifier.
power inverter See CHOPPER POWER SUPPLY. power reactive See REACTIVE VOLT-AMPERE.
power-level indicator 1. See DB METER. 2. See power rectifier A heavy-duty semiconductor diode
OUTPUT POWER METER. used to rectify alternating current for power-
power line The line through which electrical en- supply purposes.
ergy is received by a subscriber. power relay A heavy-duty relay designed to switch
power-line communication Abbreviation, PLC. significant amounts of power. The heavy contacts
Carrier-current telephony or telegraphy over and armature require high actuating current;
power lines that are common to transmitting and this necessitates a larger coil than is used in
receiving stations. Also see WIRED WIRELESS. lighter-duty relays.
power-line filter 1. A heavy-duty radio-frequency power resistor A heavy-duty resistor (i.e., one de-
(RF) filter inserted in the power line close to a de- signed to carry large currents without overheating).
vice that generates RF energy, such as a radio power stack A selenium rectifier consisting of a
transmitter. It prevents transmission of RF en- number of rectifier plates stacked in series for
ergy via the power line. 2. An RF filter inserted in higher voltage handling.
the power line, where it enters the power supply power supply 1. A device, such as a generator or a
of a sensitive electronic device, such as a com- transformer-rectifier-filter arrangement, that pro-
puter or high-fidelity audio amplifier. It prevents duces the power needed to operate an electronic
RF energy on the power line from entering the de- equipment. 2. A reserve of available power (e.g.,
vice via the power supply. the power line, an installation of batteries, etc.).
power-line frequency The frequency of the alter- power-supply filter A low-pass filter that is used
nating current and voltage available over com- to remove the ripple from the output of a power-
mercial power lines. In the United States, it is supply rectifier. See, for example, BRUTE-FORCE
60 Hz; in some countries, it is 50 Hz. FILTER.
power-line monitor An expanded-scale alternat- power-supply rejection ratio The ratio of the out-
ing-current voltmeter for the continuous moni- put-voltage change for an amplifier, oscillator, or
toring of power-line voltage. other circuit, to the change in power-supply volt-
power-line pickup The interception of radio- age. It is determined on an instantaneous basis.
frequency energy by utility power lines acting as power-supply sensitivity In an operational ampli-
receiving antennas. This energy can enter a sensitive fier, sensitivity of the offset to variations in the
electronic device, such as a computer or a high- power-supply voltage.
fidelity audio amplifier, via the power supply. power surge 1. A momentary increase in the volt-
power loss The power dissipated in a component. age on a utility line. 2. An abnormally high volt-
It generates heat while doing no useful work. age that sometimes exists for the first several
Represents energy loss, except when the genera- milliseconds after utility power is restored follow-
tion of heat is the end purpose. ing a blackout.
551
power switch • preamplifier


Filter power user In personal or business computing, a
chokes serious user who has extensive, up-to-date
knowledge of hardware and software.
power winding In a magnetic amplifier or sat-
urable reactor, the output winding (i.e., the wind-
+ +
ing through which the controlled current flows).
Poynting vector In an electromagnetic wave, the
Filtered
From vector product of instantaneous electric intensity
dc
rectifier and magnetic intensity.
PP Abbreviation of peripheral processor.
’ ’ PP 1. Symbol for PLATE POWER. 2. Symbol for
PEAK POWER.
ppb Abbreviation of parts per billion.
PPI Abbreviation of PLAN POSITION INDICATOR.
pp junction In a semiconductor wafer, the bound-
ary between two p-type regions that have some-
power-supply filter what different properties.
PPM Abbreviation of PULSE-POSITION MODULA-
TION.
power switch The switch for controlling power to a
ppm 1. Abbreviation of parts per million. 2. Abbre-
piece of equipment. Also see ON-OFF SWITCH.
viation of pulses per minute.
power switching Switching operating power on
pps Abbreviation of pulses per second.
and off. There are two principal methods: One in-
ppt Abbreviation of parts per thousand.
volves making and breaking the connections be-
PPV Abbreviation of PAY PER VIEW.
tween equipment and the power line; the other
Pr Symbol for PRASEODYMIUM.
involves making and breaking the output of a
practical component A circuit component consid-
line-operated or battery-type power supply.
ered in proper combination with the stray compo-
power tetrode A heavy-duty tetrode vacuum
nents inherent in it. Thus, a resistor has residual
tube designed to deliver relatively high output
inductance and capacitance, an inductor has
power.
residual capacitance and resistance. Compare
power-to-decibel conversion Abbreviation, PdB.
IDEAL COMPONENT.
Power expressed in decibels, with respect to a ref-
practical units A set of physical/electrical units
erence power level. Determined by the formula
especially suited to a particular application. For
PdB = 10 log10(Px/Pref ), where Px is the given power
example, in direct-current electrical applications,
level and Pref is the reference power level.
practical units are the AMPERE, OHM, VOLT,
power transfer 1. The passage of power from a
and WATT.
generator to a load. 2. The passage of power from
praetersonics See ACOUSTOELECTRONICS;
one circuit to another.
ACOUSTIC DELAY LINE; SURFACE-WAVE AM-
power transfer theorem See MAXIMUM POWER
PLIFIER; SURFACE-WAVE FILTER.
TRANSFER THEOREM.
pragilbert The unit of MAGNETOMOTIVE FORCE
power transformer A transformer designed solely
in the absolute mks (Giorgi) system.
to supply operating power to electronic equip-
pragilbert per weber The unit of RELUCTANCE in
ment”either directly or through a rectifier-filter
the absolute mks (Giorgi) system.
circuit. Because a power transformer is used at
praoersted The unit of MAGNETIZING FORCE in
low (power-line) frequencies, its core does not re-
the absolute mks (Giorgi) system.
quire the high-grade iron used in audio trans-
praseodymium Symbol, Pr. A metallic element of
formers, nor are special winding techniques
the rare-earth group. Atomic number, 59. Atomic
needed to reduce the leakage inductance and in-
weight, 140.908.
terwinding capacitance.
preaccelerating electrode In the electron gun of a
power transistor A heavy-duty transistor designed
cathode-ray tube, the high-voltage electrode that
for power-amplifier and power-control service.
provides initial acceleration to the electron beam.
power triode A heavy-duty triode vacuum tube de-
pre-alarm signal An audio and/or visual indicator
signed to deliver relatively high output power.
that an alarm will sound if an area is not cleared
power tube A heavy-duty electron tube designed to
within a short time. An example is a voice record-
deliver useful amounts of power. See, for exam-
ing in a car alarm system (e.g., “Stand back!”).
ple, POWER PENTODE, POWER TETRODE, and
preamplifier 1. A high-sensitivity, low-noise am-
POWER TRIODE.
plifier that usually uses a high-gain field-effect
power unit 1. A power supply (see POWER SUP-
transistor (FET) and is used to enhance the
PLY, 1). 2. A unit of power measurement. See,
sensitivity of a radio communications receiver.
for example, KILOWATT, MEGAWATT, MICRO-
They are especially used at frequencies above
WATT, MILLIWATT, PICOWATT, and WATT.
552 preamplifier • preset counter


preconduction current 1. The cutoff current in a
transistor. 2. In a thyratron, the small (anode)
Output current flowing before the tube is fired.
predetermined counter A counter programmed to
count to a desired number and stop.
predistortion See PREEMPHASIS.
pre-Dolby 1. To record a tape with DOLBY com-
+
pression. 2. A tape that has been recorded with
Dolby compression.
preemphasis In frequency modulation, the intro-
duction of a rising-response characteristic (re-
sponse rises as modulation frequency increases).
Compare DEEMPHASIS.
preamplifier
preequalization 1. In sound recording and repro-
duction, equalization during recording. 2. See
PREEMPHASIS.
approximately 15 MHz, where most of the noise
preferred values of components A number sys-
comes from the receiver, rather than from outside
tem used by the Electronics Industries Associa-
sources. 2. A low-noise amplifier used for boost-
tion (EIA) for establishing the values of
ing weak signals for television reception. 3. A low-
composition resistors and small fixed capacitors.
noise, low-level amplifier used for boosting signal
prefix multiplier See MULTIPLIER PREFIX.
levels from transducers, such as microphones or
prefix notation As used with complex expressions
photocells.
involving many operators and operands, a type of
prebiased relay A relay through which is main-
notation in which the expressions, rather than
tained a steady current that is just lower than
containing brackets, are given a value, according
that needed to close the relay. The actuating sig-
to the relative positions of operators and
nal, then, need only be a small amount of addi-
operands.
tional current.
preform 1. A small wafer, usually dry-pressed
precedence effect See FUSION, 1.
from powdered plastic, from which the body of a
precipitation 1. Water falling from the atmosphere
component, such as a capacitor or resistor, is
in some form (rain, snow, hail, or sleet). See PRE-
heat-molded. Also called a pill or biscuit. 2. The
CIPITATION STATIC. 2. The amount of precipita-
preformed slab used in molding a phonograph
tion occurring in a given period of time at a
disc. 3. To shape a moldable circuit before fixing
specific location. 3. Separation of a solid material
the final configuration or package.
from a solution, as a result of a chemical or phys-
preliminary information For manufactured elec-
ical action.
tronic components, data that is released prior to
precipitation static 1. Radio noise that some-
the actual availability of the device. Subject to
times occurs when it rains or snows. It can be
change when units are produced.
mistaken for artificially generated noise. 2. Radio
premix A molding compound of reinforced plastic.
noise caused by atmospheric electricity arising
prerecorded disc A phonograph disc on which a
from rain, snow, ice crystals, hail, or dust clouds,
recording has been made (i.e., a recorded disc).
through which an aircraft carrying the radio flies.
prerecorded tape Magnetic tape on which a pro-
precipitator See DUST PRECIPITATOR.
gram or data has been recorded. Also called
precipitron See DUST PRECIPITATOR.
RECORDED TAPE.
precision 1. Pertaining to electronic hardware, es-
p region See P LAYER.
pecially test instruments and measuring devices,
prescaler A device operated ahead of a counter to
designed and built to function with a high degree
establish a new, usually higher-frequency, range
of accuracy. 2. The relative accuracy of a meter or
over which frequency measurements can be
other indicating device. 3. The accuracy of the re-
made.
sults of an experiment, test, or measurement.
preselector A tuned or untuned radio-frequency
precision approach radar A radar aimed along the
amplifier operated ahead of a radio or television
approach path to guide an aircraft during ap-
receiver to boost the sensitivity of the receiver.
proach.
presence 1. In sound reproduction, the quality of
precision instrument An instrument possessing
being true to life. 2. The effect of boosted upper-
high accuracy and stability (i.e., one capable of
midrange frequencies in music.
reproducing readings or settings for various trials
preset counter A pulse counter that delivers one
under set circumstances).
output pulse for a number of successive input
precision potentiometer 1. A POTENTIOMETER
pulses, determined by the settings of counter-
possessing highly accurate resistance calibra-
circuit controls. Thus, a preset counter might
tion, linearity, and repeatability of settings. 2. A
give an output pulse for each train of 125 input
potentiometer-type voltage-measuring instru-
pulses.
ment.
553
preset element • primary coil


preset element In automation and control, an ele- This one-sided exposure results in the displace-
ment that can be preset to a given level or value, ment of the diaphragm by an amount proportional
and to which other elements can then be referred. to the instantaneous pressure of the sound waves.
preset switch In the circuit of a PRESET COUN- pressure pad In a tape recorder, a small pad that
TER, a multiposition rotary switch that can be set holds the tape against one of the heads.
to determine the number of input pulses that pressure pickup See PRESSURE TRANSDUCER.
must be received for the circuit to deliver one pressure roller In a tape recorder, a rubber-tired
output pulse. roller that presses the tape against the capstan.
preshoot A downward-moving transient pip that pressure sensor A device that detects the presence
sometimes precedes the rise of a pulse. of, and/or measures, physical force within a spe-
cific area. One simple device uses two metal
plates separated by electrically resistive foam.
Pressure compresses the foam and reduces the
resistance between the plates. This resistance
Relative amplitude




change can be detected and measured.
pressure switch A switch that is opened or closed
by a change in pressure within a system.
pressure transducer A sensor for converting pres-
sure into proportionate current or voltage. Some
Preshoot Time use strain gauges; others use piezoelectric crys-
tals, potentiometers, and other variable elements.
pressure zone A region of high air pressure that is
’ immediately adjacent to a surface reflecting an
acoustic (sound) wave.
preshoot pressure-zone microphone A microphone equip-
ped with a deflector that helps to guide acoustic
preshoot amplitude The peak voltage of a PRE- energy toward the diaphragm.
SHOOT, measured from the zero line to the valley prestore To place data in memory before it is in-
of the preshoot. tended for use.
preshoot time The width of a PRESHOOT, mea- pretuned stage A stage, such as one in an inter-
sured along the horizontal base line (time axis). mediate-frequency amplifier or single-frequency
pressing 1. A process by which phonographic receiver, that is preset to a frequency, rather than
discs are fabricated from plastic. 2. A disc being continuously tuned.
pressed from plastic. prf Abbreviation of PULSE REPETITION FRE-
press-to-talk microphone A microphone that QUENCY.
uses a PRESS-TO-TALK SWITCH for actuation. pri Abbreviation of PRIMARY.
press-to-talk switch A switch in a microphone or primaries See PRIMARY COLORS.
on the end of a control cord. It is used to actuate primary 1. See PRIMARY WINDING. 2. See PRI-
a transmitter, telephone, or recorder when the MARY STANDARD.
operator wishes to speak. primary battery A battery composed of primary
pressure Abbreviation, P or p. 1. Force per unit cells.
area. It can be expressed in any appropriate units primary block A fundamental group of channels in
of force and area (e.g., newtons per square meter, pulse-code modulation, combined by means of
pounds per square inch, grams per square cen- time-division multiplexing.
timeter, etc.). 2. The application of force over part primary capacitance 1. The distributed capaci-
or all of a surface. 3. Compression. 4. See TEN- tance of the primary winding of a transformer
SION, 1. whose secondary winding is unloaded. Compare
pressure amplitude The pressure caused by an SECONDARY CAPACITANCE, 1. 2. A series or
acoustic disturbance. It is usually measured in shunt capacitance used to tune the primary coil
dynes per square centimeter. of a radio-frequency transformer. Compare SEC-
pressure capacitor An enclosed fixed or variable ONDARY CAPACITANCE, 2.
capacitor, whose breakdown voltage increases primary cell An electrochemical cell that does not
when the air pressure rises inside the container. require, and generally will not accept, an electri-
pressure contact 1. Electrical contact made by cal charge in order to function. Once it has been
pressing two conducting surfaces together (to discharged, the cell must usually be thrown
complete a circuit). 2. A contact for obtaining the away. Compare STORAGE CELL. Also see CELL,
condition described in 1. DRY CELL, and STANDARD CELL.
pressure-gradient microphone See PRESSURE primary circuit 1. The circuit associated with the
MICROPHONE. primary winding of a transformer. 2. The circuitry
pressure microphone A microphone that receives associated with the input to a device or system.
sound waves at only one side of its diaphragm. primary coil See PRIMARY WINDING.
554 primary colors • print


primary colors See COLOR PRIMARY. primary utilization factor Abbreviation, UFp. For
primary current The current flowing in the pri- a transformer in a rectifier circuit, the ratio of
mary winding of a transformer. Also called direct-current power output to primary volt-
TRANSFORMER INPUT CURRENT. Compare amperes. Numerically, the primary utilization
SECONDARY CURRENT. factor is higher than the secondary utilization
primary electron The electron possessing the factor, but is less than 1. Also see SECONDARY
greater energy after a collision between two elec- UTILIZATION FACTOR and UTILITY FACTOR.
trons. Compare SECONDARY ELECTRON. primary VA The volt-amperes in the input circuit
primary emission Emission arising directly from a of a transformer. Compare SECONDARY VA.
source, such as the cathode of an electron tube. primary voltage The voltage across the primary
Compare SECONDARY EMISSION. winding of a transformer. Also called transformer

<<

. 30
( 42)



>>