Source: 

The source can be an analog signal. Example: A Sound signal.


Input Transducer:

This is a transducer which takes a physical input and converts it to an electrical signal (Example: microphone). This block also consists of an analog to digital converter where a digital signal is needed for further processes. A digital signal is generally represented by a binary sequence.


Source Encoder

The source encoder compresses the data into minimum number of bits. This process helps in effective utilization of the bandwidth. It removes the redundant bits.


Channel Encoder:

The channel encoder, does the coding for error correction. During the transmission of the signal, due to the noise in the channel, the signal may get altered and hence to avoid this, the channel encoder adds some redundant bits to the transmitted data. These are the error correcting bits.


Source Decoder:

The resultant signal is once again digitized by sampling and quantizing so that the pure digital output is obtained without the loss of information. The source decoder recreates the source output.

Output Transducer:

This is the last block which converts the signal into the original physical form, which was at the input of the transmitter. It converts the electrical signal into physical output (Example: loud speaker).

Output Signal:

This is the output which is produced after the whole process. Example − The sound signal received.

Advantages of Digital Communication:-

As the signals are digitized, there are many advantages of digital communication over analog communication, such as −
The effect of distortion, noise, and interference is much less in digital signals as they are less affected.
Digital circuits are more reliable.
Digital circuits are easy to design and cheaper than analog circuits.
The hardware implementation in digital circuits, is more flexible than analog.
The occurrence of cross-talk is very rare in digital communication.
Signal processing functions such as encryption and compression are employed in digital circuits to maintain the security of the information.
The probability of error occurrence is reduced by employing error detecting and error correcting codes.
The configuring process of digital signals is easier than analog signals.
Digital signals can be saved and retrieved more conveniently than analog signals.
Many of the digital circuits have almost common encoding techniques and hence similar devices can be used for a number of purposes.
The capacity of the channel is effectively utilized by digital signals.