Glossary
Term | Main definition |
---|---|
Plasticizer |
A chemical added to plastics to make them softer and
more flexible.
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Plenum |
The air-handling space between the walls, under
structural floors, and above drop ceilings when used
to circulate and otherwise handle air in a building.
Plenum-grade cable can be run through these spaces if
local building codes permit it.
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Plenum cable |
Cable whose flammability and smoke characteristics
allow it to be routed in plenum spaces without being
enclosed in a conduit; all cables with this rating must
pass NFPA 262 (formerly UL 910).
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Plug |
The male component of a plug/jack connector system. In
premises cabling, a plug provides the means for a user to
connect communications equipment to the communications
outlet.
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PM Phase modulation | One of three basic methods of adding information to a sine wave signal in which its phase is varied to impose information on it. See also amplitude modulation and frequency modulation.
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Point-to-point transmission |
Carrying a signal between two endpoints without
branching to other points.
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Polarity |
Identifies which side of an electrical circuit is positive
and which is negative.
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Polarization |
(1) Alignment of the electric and magnetic fields that
make up an electromagnetic wave. Normally refers to
the electric field. If all light waves have the same alignment,
the light is polarized. (2) The direction of vibration
of the photons in the light wave.
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Polarization maintaining fiber |
Optical fiber that maintains the polarization of light that
enters it.
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Polarization mode dispersion |
Spreading of the light wave caused by imperfections in a
single-mode optical fiber that slow down a polarization
mode of the signal. When one polarization mode lags
behind another, the signal spreads out and can become
distorted.
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Polarization stability |
The degree of variation in insertion loss as the polarization
state of the input light is varied.
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Polling |
A media access control method that uses a central device
called a controller, which polls each device in turn and
asks if it has data to transmit. 100VG-AnyLAN hubs poll
nodes to see if they have data to transmit.
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Polybutadiene |
A type of synthetic rubber often blended with other synthetic
rubbers to improve their dielectric properties.
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Polyimide |
A polymer that is used to coat optical fiber for harsh
environment applications.
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Polymer |
A substance made of repeating chemical units or molecules.
The term is often used as a synonym for plastic,
rubber, or elastomer.
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