panning The side-to-side movement
of sounds and images from one location to another. Originally a camera term.
pan & scan A method of
converting a widescreen presentation to an image within a 4:3 aspect ratio without
black bars at the top and bottom of the picture. The camera moves back and forth
(panning and scanning) in each scene to show only the most important parts of
the image. Results in the left and/or right edges of the image being cut off.
passive subwoofer
A speaker for reproducing bass
frequencies that must be powered by a separate
power amplifier. Contrasted with “active”
or“powered” subwoofers, which contain
built-in amplifiers.
PCM See “Pulse
Code Modulation.”
peak A short-term, high-level audio
signal.
perceptual coding
A method of reducing the number of bits needed to encode an audio or video signal
by ignoring information unlikely to be heard or seen. Also called “lossy
compression.”
phantom
center-channel mode A setting on A/V receivers
or A/V controllers invoked
when no center-channel speaker is used.
phantom image The
creation of an apparent sound source between two speakers.
phase In a periodic wave, the
fraction of a period that has elapsed. Describes the time relationship between
two signals.
phase adjustment
A control provided on some subwoofers that lets
you delay the sound of the subwoofers lightly so
that its output is in phase (has the same time relationship) with the output of
the front speakers.
pixel The smallest element in
a displayed video image. Image resolution is measured in pixels; the greater the
number of pixels, the higher the resolution.
plasma display
panel (PDP) Fixed-pixel video display device in which an electrical charge
ionizes gas inside a glass-matrix array, causing phosphors on the glass to emit
light. Current plasma panels range in size from 42 to 71 inches, and are about
three inches thick.
port Opening in a loudspeaker
cabinet that channels bass from inside the enclosure
to outside the enclosure. Also called a “vent.”
power amplifier
An audio component that boosts a line-level signal to a powerful signal that can
drive loudspeakers.
power handling
A measure of how much amplifier power, in watts, a speaker can take before it
is damaged.
power output A measure
of a power amplifier’s ability, in watts,
to deliver electrical voltage and current to a speaker.
power supply Circuitry
found in every audio and video component that converts 60Hz
alternating current from the wall outlet into direct current that supplies the
device’s circuitry.
power transformer
Device in a power supply that reduces the incoming voltage from 120V to a lower
value.
progressive
scanning A method of creating an image on a video monitor by displaying
the scanning lines sequentially from top to bottom. Contrast with “interlaced
scanning.”
pulse code
modulation (PCM) A method of representing an audio signal as a series
of digital samples. Circuitry found in every audio
and video component that converts 60Hz alternating current
from the wall outlet into direct current that supplies the device’s circuitry.
power transformer
Device in a power supply that reduces the incoming voltage from 120V
to a lower value.