3-27
Figure 3-23.—Pcm conversion.
When the pcm demodulator recognizes the presence or absence of pulses in each position, it
reproduces the correct standard amplitude represented by the pulse code group. For this reason, noise
introduces no error if the largest peaks of noise are not mistaken for pulses. The pcm signal can be
retransmitted as many times as desired without the introduction of additional noise effects so long as the
signal-to-noise ratio is maintained at a level where noise pulses are not mistaken for a signal pulse. This is
not the only method for demodulating pcm, but it is one of the simplest.
This completes your study of demodulation. You should remember that this module has been a basic
introduction to the principles of modulation and demodulation. With the advent of solid-state electronics,
integrated circuits have replaced discrete components. Although you cannot trace the signal flow through
