Pulse code Modulation the involves Sampling,Quantization, and Reconstruction.

Pulse code modulation techinique basically involves Sampling , Quantization , Reconstruction.

SAMPLING : The analog signal is sampled by multiplying it with an impulse train generates all the sample values.

QUANTIZATION : The sample values being only discrete in Time must also be made discrete in Amplitude also by the process of Quantization.

                                               ACCORDING TO THE RULE OF QUANTIZATION 
                                               
                                               X[N] = rk  if tk < X[n] < tk+1
                                               
                                               X[n] Sampled value
                                               rk - reconstruction level
                                               tk - quantization levels

RECONSTRUCTION : Using a low pass butter worth filter of sufficient bandwidth and order = 2.