o
The metal casing prevents the penetration of EM noise
o It also can eliminate a phenomenon called
Crosstalk, which is the undesired effect
of
one circuit (or channel) on another circuit (or channel)
o It occurs when one one line picks up some
of the signals traveling down another
line.
o This effect can be experienced during
telephone conversations when one can hear
other
conversations in the background
o Shielding each pair of twisted pair can
eliminate most crosstalk
o STP
Cable has the
same quality considerations and
uses the same
connectors as
UTP
but the shield must be connected to a ground
o STP is more expensive than UTP but is
less susceptible to noise
™ Coaxial Cable
o Instead of having two wires, coaxial
cable has a central core conductor of solid or
stranded
wire (usually copper) enclosed in an insulating sheath
o This is in turn encased in an outer
conductor of metal foil, braid or a combination
of
the two
o The
outer metallic wrapping
serves both as
a shield against
Noise and as
the
second
conductor which completes the circuit
o This outer conductor is also enclosed in
an insulating sheath and the whole cable
is
protected by a plastic cover
|
Shielded
Twisted Pair (STP)
o Has
a metal foil
or braided-mesh covering
that encases each
pair of insulated
conductors
|
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