MEDIA, WAVES, & SIGNALS:

1.  Transmission Media:

The different forms of information (data, sound, image, video)
are sent by waves (electro magnetic, radio, light) along
different media (twisted pair, coax, fiber) or through space.

Different media have different carrying capacity of waves and
hence, different carrying capacity of information.  

a.  Twisted pair is cheap, universal, but slow and subject to 
interferrence & noise.
b.  Co-ax is more expensive, but faster and shielded from external
noise.
c.  Fiber comes from cheap natural resource, is technically
complex, switching is not fast, but transmission is very fast.
d.  Microwave (terrestrial & geo-stationary satellite) is fast, 
expensive, can travel through space.  

2.  Wave Theory:
Waves of different origins (water, air, light) have
similar characteristics (e.g. amplitude, phase, frequency & period). 

3.  Signal carrying waves are modulated (AM, FM, PM) to produce 
information signals (on/off).  An on/off signal is represented
by several waves.  The more waves per on/off signal, the "sharper"
the bit signal.

3.  Frequency Spectrum:
The frequency spectrum is a one dimensional
continuum that shows ascending frequencies and the various 
classifications and uses of those frequencies.

Notes:
The following list shows typical media and times to transmit a 2Megabit
file (e.g. a simple still image)

a. Traditional analog phone line (1.2 min.)
b. ISDN digital phone line (35.7 sec.)
c. T-1 phone line (1.3 sec.)
d. Co-ax cable (.5 sec.)

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