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Building blocks of communication systems

19 January, 2016 - 14:56

You’ll learn the design and applications of communication systems in this course. So, as you work toward your first reading, the first idea you need to understand is the building blocks of a communication system.

A communication system should consist of at least one source, one sink (destination) and a channel. Examples of communication systems that contain:

  1. a single source and a single sink; and
  2. a single source and multiple sink;

are shown in Figure 1.1.

Figure 1.1 Examples of communication systems

At one end, the information will be transmitted from the source through a medium (i.e., the channel) to the destination (called the sink), which is the other end point.

Let’s take a chat with your friend as an example:

You voice out a message to your friend through the air.

That’s to say, you are one of key components in this communication system.

Similarly, you should already be aware of other types of communication systems  in daily use. All of these systems are essentially similar to the voice conversation described above — the technology used is obviously different. Let’s consider a typical process in a telephone system as an example.

Other types of communication systems found in our daily life

  • Telephone systems
  • Commercial radio
  • Television
  • Satellite systems
  • Mobile cellular telephone systems
  • Fax
  • Internet

Typical process in a telephone system

  1. When the speaker speaks at the transmitting end, the telephone converts his or her voice into an electrical signal.
  2. The electrical signal is transmitted over a link to a telephone network.
  3. The telephone network routes the signal to the receiving end according to the phone number dialled.
  4. At the receiving end, the electrical signal is converted back to voice. Therefore, the receiving party is able to listen to the speech.

This is a simple explanation of the idea of a communication system. You will learn a lot more about these basic concepts throughout this unit, which will help you to build up a complete picture of the subject.

The terms used to describe the building blocks of communication systems might be different in other reference books. Here are some equivalent terms:

Equivalent term


Input transducer

A device that converts the original message to a suitable form for transmission.


The medium of the communication path, sometimes also called link

Output transducer

A device that converts the output signal at the receiver back to the original signal form.