INCESSANT TRANSMISSION 9/16 



the paper, then the marks will affect his retina and so on to his 

 brain where an interaction will occur with the trace (whatever that 

 may be) of "118213"; he will then give a final answer. What we 

 must notice here is that this process, from brain, through motor 

 cortex, arm, pencil, marks, light rays, retina, and visual cortex back 

 to brain, is, to the communication engineer, a typical "channel", 

 linking "transmitter" to "receiver". To the cyberneticist, therefore, 

 the white matter, and similar fibres, are not the only channels of 

 communication available to the brain : some of the communication 

 between part and part may take place through the environment. 



9/16. Redundancy. In S.7/14 it was stated that when a constraint 

 exists, advantage can usually be taken of it. An illustration of this 

 thesis occurs when the transmission is incessant. 



For simplicity, reconsider the traffic lights — Red, Yellow, and 

 Green — that show only the combinations 



(1) Red 



(2) Red and Yellow 



(3) Green 



(4) Yellow. 



Each component (each lamp or colour) can be either fit or unfit, 

 so the total variety possible, if the components were independent, 

 would be 8 states. In fact, only 4 combinations are used, so the 

 set shows constraint. 



Now reconsider these facts after recognising that a variety of four 

 signals is necessary: 



(i) Stop 



(ii) Prepare to go 

 (iii) Go 

 (iv) Prepare to stop. 



If we have components that can each take two values, + or — , we 

 can ask how many components will be necessary to give this variety. 

 The answer is obviously two; and by a suitable re-coding, such as 



+ + = Stop 



H — = Prepare to go 



-- = Go 



— h = Prepare to stop 



the same variety can be achieved with a vector of only two compo- 

 nents. The fact that the number of components can be reduced 

 (from three to two) without loss of variety can be expressed by 



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