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DATA COMMUNICATIONS
Copyright Brian Brown, 1995-2000. All rights reserved.

Part 1: Introduction to Communications

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Overview | Shannon's Model | Modes of communication
Thinking Exercise | Summary | References


Overview of Communications
The need to communicate is part of mans inherent being. Since the beginning of time the human race has communicated using different techniques and methods. Circumstances and available technology have dictated the method and means of communications. Many early forms of communication were writing, depicted on cave walls. Then communication advanced by the development of language and the use of symbols. Papyrus and paper were used to record communication for later use. Smoke signals of the early american Indians; the drums of African tribes; and the towers of the chinese wall are indications of the desire to communicate beyond the immediate physical boundaries of space. Story tellers around the camp-fire are a good example of communication, using animation, gestures and sound to communicate their message to other members of the tribe.

In 1948, a model of communication was proposed by Claude Shannon. Shannon worked for the Bell Telephone Company in America, and was concerned with the transmission of speech across a telephone line. Warren Weaver, in association with Shannon, wrote a preface to this model and it was published as a book in 1949. Weaver saw the applicability of Shannon's model of communication to a much wider sphere than just telephony, and it has served as a basis for explaining communication since that time.

Shannon model
Shannons Model of Communication

In terms of oral communication between two people, the model is applied as follows.

Message The idea, thought
Source The brain
Sender The transmitting device, the mouth
Channel The medium the message travels over, air
Receiver The receiving device, the ear
Destination The brain

In any communication there is noise, which affects the message as it travels across the channel from the sender to the receiver. Shannon proposed building in redundancy, which was added to the transmitted message in order for it to be reliably detected at the receiver. Let us apply this model to a telephone conversation between two people. The person that initiates the call by lifting the telephone handset and dialing a number is the SOURCE, their telephone the SENDER, whilst the person who answers the ringing telephone is the DESTINATION and their telephone the RECEIVER. The CHANNEL is the Public Telephone Switched Network (PTSN), and the MESSAGE is the topic of conversation [speech] that was the reason for the call being made.

 

Exercise
Apply Shannon's model of communication to the following pictures, by identifying the source, sender, channel, receiver, destination and message elements.

air traffic controllerbears fighting

 

Problems of Shannon's Model
However, Shannon's model has a number of problems as a model for explaining communication.


Modes of Communication
There are a number of commonly accepted divisions or layers of communication. The following table lists the more common layers that form the basis of modern courses in communications.

Communication Type Explanation
Intra Personal Communication one has with oneself, thoughts, daydreaming
Inter Personal Communication one has with another person
Group Communication one has with a group of people (group discussion, party)
Organizational Communication within or between organizations (newsletters, memos)
National Communication within or between nations (trade, war)
Global Communication on a global scale that affects all people on the planet (greenhouse effect)

 

Look at the following images. Try to categorize each picture into the appropriate layer of communication outlined in the previous table.

groupintranationalinterpersonal


think.gif (2560 bytes) Something to think about
Spend a few moments thinking about some of the methods of communication used today, such as radio, television, news-papers, fax, phone and Internet. Are they one-way, two-way, multiple or interactive? How can user participation be encouraged (classic case is talk back radio, and music requests)? What reasons can you think of for encouraging user participation in traditionally one way methods of communication?

In addition, a message is sometimes delivered in different formats, for example, sound (as in clicks and whistles between dolphins), as printed text in newspapers, as sound waves in speech, sometimes as electromagnetic radio waves or light. What criteria do you think must exist if the sender and receiver are to inter-communicate effectively?

And another thought... under what occassions might you want the message to be secure so that other parties who might be listening in would not know the content of the message?


Summary
Communication takes place all around us. Mankind has communicated in various ways since the beginning of their existence, by means of drawings, writings, signals, symbols and language.

Shannon's model of communication serves as a basis for explaining communication, but it has limitations, an example is that it does not explain the meaning of the message.

There are many levels of communication, from inter, intra, group, organizational, national to global. We can also speak of animal communication and computer mediated communication, where the computer mediates the message. In the information age, much of the communication we receive each day is mediated in some way by technology.


Further Internet based references
Assyrian lion hunt frieze at the British Musuem. http://www.british-museum.ac.uk/highligh.htm#Dying
The Rosetta Stone at the British Musuem. http://www.british-museum.ac.uk/highligh.htm#Rosetta

Torches and Beacons Gerard Holzmann, Bjorn Pehrson.
http://www.it.kth.se/docs/early_net/ch-1-1.html
Chandler, Doug. The Transmission Model of Communication.
http://www.aber.ac.uk/~dgc/trans.html
Weaver, Warren. Brief Excerpts from Warren Weaver’s Introduction to: Claude Shannon’s The Mathematical Theory of Communication
http://darkwing.uoregon.edu/~felsing/virtual_asia/info.html
Summary of Communication Theories. Brian Brown.
http://www.cit.ac.nz/staff/brownbr/mcomms/comm501/theories.htm


I am indebted to Professor John Tiffin, Victoria University of Wellington, for the insights and thoughts expressed in this section.


Copyright B Brown. 1995-2000. All rights reserved.
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