Modulation and Demodulation
Modulation
In Context to a
modem, the modulation process involves the conversion of the
digital computer signals ( logic 1 and Logic 0 states) to
analog audio-frequency (AF) tones. Digital highs are renewed
to a tone having a certain constant pitch; digital lows are
transformed to a tone having a varying constant pitch. These
states change very quickly making a hiss sound as an output
of the computer modem. The demodulation process converts the
audio tones back into digital signals that are computer
friendly as described below.
Demodulation
Demodulation is
the process of decoding an analog signal into digital data.
When data is shifted over phone lines, a modem modulates the
data into audible tones carried on frequencies between 0 Hz
and 4 KHz. Once the data reaches its required destination,
another modem demodulates the signal back into digital data.
Cable TV networks also use modulation techniques to transfer
data.
