ANALOG TO DIGITAL CONVERSION

                          If we've an analog signal like one created by a microphone or camera. to alter an analog signal to digital data we use two techniques, pulse code modulation and delta modulation. After the digital data are created (digitization) then we convert the digital data to a digital signal.

1. Pulse Code Modulation (PCM):

                          Pulse Code Modulation (PCM) is that the most typical technique wont to change an analog signal to digital data (digitization). A PCM encoder has three processes as shown within the following Figure.

The analog signal is sampled.
The sampled signal is quantized.
The quantized values are encoded as streams of bits.

2. Sampling

                          Sampling as its name suggests will be defined as take samples. Take samples of a digital signal over x axis. Sampling is completed on an experimental variable. Sampling is completed on the x variable. we are able to also say that the conversion of x axis (infinite values) to digital is completed under sampling.
     
Sampling is further divide into up sampling and down sampling. If the range of values on x-axis are less then we are going to increase the sample of values. this is often referred to as up sampling and its the other way around is thought as down sampling.

3. Quantization

                        Quantization as its name suggest will be defined as dividing into quanta (partitions). Quantization is completed on variable quantity. it's opposite to sampling.
In case of this mathematical equation y = sin(x)
Quantization is completed on the Y variable. it's done on the y axis. The conversion of y axis infinite values to 1, 0, -1 (or the other level) is thought as Quantization.