11/16 AN INTRODUCTION TO CYBERNETICS 



SOME VARIATIONS 



11/16. In S.11/4 the essential facts implied by regulation were 

 shown as a simple rectangular table, as if it were a game between two 

 players D and R. The reader may feel that this formulation is 

 much too simple and that there are well known regulations that it is 

 insufficient to represent. The formulation, however, is really much 

 more general than it seems, and in the remaining sections of this 

 chapter we shall examine various complications that prove, on 

 closer examination, to be really included in the basic formulation 

 of S.11/4. 



11/17. Compound disturbance. The basic formulation of S.11/4 

 included only one source of disturbance D, and thus seems, at first 

 sight, not to include all those cases, innumerable in the biological 

 world, in which the regulation has to be conducted against several 

 disturbances coming simultaneously by several channels. Thus, a 

 cyclist often has to deal both with obstructions due to traffic and 

 with disequilibrations due to gusts. 



In fact, however, this case is included; for nothing in this chapter 

 excludes the possibility that D may be a vector, with any number of 

 components. A vectorial D is thus able to represent all such 

 compound disturbances within the basic formulation. 



11/18. Noise. A related case occurs when T is "noisy" — when T 

 has an extra input that is affected by some disturbance that interferes 

 with it. This might be the case if T were an electrical machine, 

 somewhat disturbed by variations in the mains' voltage. At first 

 sight this case seems to be not represented in the basic formulation. 



It must be appreciated that D, T, E, etc. were defined in S.11/3 

 in purely functional form. Thus "i)" is "that which disturbs". 

 Given any real system some care may be necessary in deciding what 

 corresponds to D, what to T, and so on. Further, a boundary 

 drawn provisionally between D and T (and the other boundaries) 

 may, on second thoughts, require moving. Thus one set of boun- 

 daries on the real system may give a system that purports to be of 

 D, T, etc. yet does not agree with the basic formulation of S.11/4. 

 Then it may be found that a shifting of the boundaries, to give a 

 new D. T, etc., gives a set that does agree with the formulation. 



If a preliminary placing of the boundaries shows that this (pro- 

 visional) T is noisy, then the boundaries should be re-drawn so as 

 to get r's input of noise (S.9/19) included as a component in D. D 



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