Lesson 6

Text: Communication

Pre-text exercises:

I. Arrange synonyms and antonyms in pairs and memorize them:

Require, function, apply, to come out of, giant, demand, to increase, hence, usually, use, modern, commonly, mainly, consequently, tiny, heat, light, raise, heavy, cool, reduce, confined, inside, outside, input, principally, to come into, slowly, to decrease, output, complicated, rapidly, simple, present-day, operate.

II. Read and translate the text: “COMMUNICATION”

The word “communication” is used very often in a very broad sense to include all of the procedures by which one mind may affect another. This involves not only written and oral speech, but also music, the pictorial arts, the theatre, the ballet and in fact all human behave our.

In some connections it may be desirable to use a still broader definition of communication, namely, one which would include the procedures by means of which one mechanism affects another mechanism. Relative to the broad subject of communication, there seem to be three problems. Thus it seems reasonable to ask: How accurately can the symbol of communication be transmitted? (The technical problem.) How precisely do the transmitted symbols convey the desired meaning? (The semantic problem.) How effectively: does the received meaning affect conduct in the desired way? (The effectiveness problem.)

The technical problems are concerned with the accuracy of transference from the sender to the receiver of sets of symbols (written speech), or of continuously varying signals (telephonic or radio transmission of voice or music), or of a continuously varying two dimensional patterns (television), etc. Mathematically, the first involves the transmission of a finite set of discrete symbols, the second the transmission of one continuous function of time and the third the transmission of many continuous functions of time, or of one continuous function of time and of two space coordinates.

A Communication System and its Problems.The communication system may be symbolically represented as in Fig. 8. The information source selects a desired message out of a set of possible messages. The selected message may consist of written or spoken words, or of pictures, music, etc. The transmitter changes this message into the signal which is sent over the communication channel from the transmitter to the receiver. In the case of telephony, the channel is a wire, the signal is a varying electrical current on this wire; the transmitter is the set of devices (telephone transmitter, etc.) which change the sound pressure of the voice into varying electrical current.

In telegraphy, the transmitter codes written words intosequences of interrupted current of varying lengths (dots, dashes, spaces). In oral speech, the information is the brain, the transmitter is the voice mechanism producing the varying sound pressure (the signal) which is transmitted through the air (the channel).

In the case of radio, the channel is simply space and the signal is the electromagnetic wave which is transmitted.

The receiver is a sort of the inverse transmitter, changing the transmitter signal back into a message, and handing this message on to the destination. In the process of being transmitted it is unfortunately characteristic that certain things are added to the signal which were not intended by the information source. These unwanted additions may be distortions of sound (in telephony, for example) or static (in radio), or distortions in shape or shading of picture (television), or errors in transmission (telegraphy or facsimile), etc. All of these changes in the transmitted signal are called noise.

The word “information”, in the mathematical theory of communication, is used in a special sense that must not be confused with its ordinary usage. In particular, information must not be confused with meaning. In fact two messages, one of which is heavily loaded with meaning and the other of which is pure nonsense, can be exactly equivalent, from the present viewpoint, as regards information.

The word “information” in communication theory relates not so much to what you do say, as to what you could say. That is, information is a measure of one's freedom of choice when one selects a message. If one is confronted with a very elementary situation where he has to choose one of two alternative messages, then it is arbitrarily said⁹ that the information associated with this situation is unity. Note that it is misleading to say that one or the other message conveys unit information. The concept of information applies not to the individual message (as the concept of meaning would), but rather to the situation as a whole, the unit information indicates that in this situation one has an amount of freedom of choice, in selecting a message, which it is convenient to regard as a standard unit amount.