18WuD2x

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