18WuD2x

peak torque • PEP transistor 521
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Amplitude
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Amplitude
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Amplitude
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pk-pk
pk-pk
pk-pk
peak-to-peak voltage
Time
Time
Time
pencil 1. A beam of electrons or other particles or
rays that either converges to, or diverges from, a
specific point. 2. A pair of geometric entities sharing
a property (e.g., lines intersecting at a single
point).
pendulum switch A device that closes a circuit
when subjected to physical shock. One type consists
of a dangling element resembling a pendulum,
with one or more nearby contacts.
penetrating frequency For a particular layer of
the ionosphere, the lowest high frequency at
which a vertically propagated wave penetrates the
layer (i.e., it is not reflected back to earth). Also
called CRITICAL FREQUENCY.
penetrating radiation Ionizing radiation that
passes through otherwise opaque materials. A
relative term; low-energy X rays are less penetrating
than high-energy X rays, which, in turn, are
less penetrating than gamma rays.
penetrating rays See COSMIC RAYS.
penetration depth See DEPTH OF PENETRATION.
pent Abbreviation of PENTODE.
pentavalent element An element whose atoms
have five valence electrons (e.g., antimony or arsenic).
pentode A five-electrode vacuum tube in which the
electrodes are an anode, cathode, control grid,
screen grid, and suppressor grid.
pentode field-effect transistor A field-effect transistor
with three separate gates.
pentode transistor A bipolar transistor with three
emitters.
peak torque Symbol, T p . For a torque motor, the
maximum useful torque at maximum recommended
input current.
peak voltage Abbreviation, E p . The highest value
reached by an alternating-current voltage half cycle,
or by a voltage pulse. Also called MAXIMUM
VOLTAGE.
peak voltmeter 1. An alternating-current (ac) voltmeter
that responds to the peak value of the applied
voltage. 2. An ac voltmeter that responds to
the average value of the applied voltage—even
though its scale reads in peak volts.
pea lamp A miniature incandescent bulb, sometimes
used as a control-panel or meter light.
PEC Abbreviation of PHOTOELECTRIC CELL.
pedestal See BLANKING PEDESTAL.
pedestal level See BLANKING LEVEL.
pel See PIXEL.
Peltier effect A drop below ambient temperature
at the junction between two dissimilar metals
when an electric current is passed through the
junction.
PEM Abbreviation of photoelectromagnetic.
pen-and-ink recorder A graphic recorder in which
a fountain-pen-type stylus inscribes an ink line
on a paper chart. Also called pen recorder.
B
C
E 1
E 2
E 3
pentode transistor
penumbra 1. That part of a shadow in which the
light source is not fully obscured by the eclipsing
object. 2. In a sunspot, the outer part of the spot;
it is less dark than the inner portion.
PEP 1. Abbreviation of PLANAR EPITAXIAL PASSI-
VATED. 2. Abbreviation of PEAK ENVELOPE
POWER.
PEP diode See PLANAR EPITAXIAL PASSIVATED
DIODE.
PEP reading wattmeter A wattmeter that shows
the peak envelope power output of a transmitter.
PEP transistor See PLANAR EXPITAXIAL PASSI-
VATED TRANSISTOR.