150
Networking Fundamentals
transmitter
an electronic device
that generates a carrier
wave and modulates
the data signal into the
carrier wave.
receiver
an electronic device
that receives a modu-
lated signal and
demodulates it.
consists of a transmitter, which generates the carrier wave and modulates
information into the carrier wave, and a receiver, which receives the modulated
wave and demodulates it. The transceiver and receiver must both be at or very
near the same carrier wave frequency for communication to occur.
Look at the example of a voice wave broadcast in Figure 4-3. In the example, a
carrier wave of 104.5 MHz, is shown. The human voice produces sound at a much
lower frequency, typically in a range from a 400 cycles per second to approximately
4,000 cycles per second. The human voice is converted into electrical energy using
a microphone. The microphone produces a pattern of electrical energy in direct
proportion to the human voice. The electrical energy is mixed with the carrier
wave. The carrier wave has a much higher frequency than the electromagnetic
wave produced by the human voice. The two are combined so that the human
voice can be transmitted.
Figure 4-2.
A carrier wave
is the means of
communication
between two
wireless devices. In
this example, a radio
station assigned the
104.5-MHz frequency
transmits data on a
104.5-MHz carrier
wave. A radio with its
dial set to 104.5 picks
up the information
broadcast from the
radio station.
104.5
Radio station
104.5-MHz
carrier wave
Figure 4-3.
Example of a voice
wave broadcast.
The speaker
converts electrical
energy into a
voice wave.
The electrical energy
produced from the
sound wave is mixed
with the carrier wave.
The transmitter
produces the
carrier wave.
104.5
104.5 MHz
The receiver accepts
the combined wave,
and then separates the
voice wave from the
carrier wave. The voice
wave is converted to
electrical energy.
The voice wave
is converted to
electrical energy.
~400 to
~4,000 MHz