o Signals
are transmitted from
one device to
another in the
form of electromagnetic
energy
o Electromagnetic signals can travel
through Vacuum, Air or other transmission media
o Electromagnetic energy, a combination of
electrical and mechanical fields vibrating in
relation
to each other includes power, voice, video, radio waves, infrared light,
visible
light
and ultra violet light
o Each of the above constitute a portion of
the Electromagnetic Spectrum:
ƒ Not all the portions of the spectrum are
currently usable for Telecommunications
ƒ Voice-band frequencies
are generally tx
as current over
metal cables, such
a
twisted
pair or coaxial cable
o Radio frequencies can travel through air
or space but require specific transmitting and
receiving
mechanisms
o Visible
light, the third
type of Electromagnetic energy
currently used for
communications
is harnessed using fiber optic cable
™ Classes of Transmission Media
o Two classes of Transmission Media:
-Guided Media
-Unguided Media
Guided Media
Guided
Media, are those media that provide a conduit from one device to
another
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