Pulse-code modulation (PCM) is similar to pulse-position modulation (PPM) in
that the received information is not determined by the shape
of the pulse, but has the additional advantage that the
precise location of the pulse is not important either. The
analogue signals are first sampled using pulse amplitude modulation. The
pulse amplitude modulation pulses are then encoded into a binary
code that is transmitted as a digital stream. At the
receiver these pulse code modulation (PCM) codes are decoded
into pulse amplitude modulation (PAM) pulses that are then used
to reconstruct the analogue waveform. In adaptive differential pulse-code modulation
(ADPCM), the binary number that is transmitted is not the
number that corresponds to the actual voltage level, but rather
the difference between the current sample value and the last.
The difference values have a smaller dynamic range and compression
(of the order of one-half) results).
Other topics in our resources on Communications Systems related to Pulse code modulation include: