12/22 AN INTRODUCTION TO CYBERNETICS 



require exact treatment in any particular embodiment, the system 

 is thus stable at a state of equilibrium whose position is determined 

 by L's position.) 



The whole can thus also be regarded as a stable system that acts 

 so that, while a movement of, say, one inch at L would tend to cause, 

 at V, a movement of one inch also, the reaction of the system annuls 

 this. So the system can also be regarded as one that acts so as to 

 keep the position ofY constant. 



We can now see how it can become a power ampUfier, and be 

 used as a crane. 



The designer takes care to see that the lever / is light, and that the 

 valve is shaped so that the escaping air, or the pressure z, has little 

 effect on the force required at L. He also takes care that B shall 

 have a large area of action on P, and that the average working 

 pressure z shall be high (with the pressure at A higher still). If he 

 is successful, a small force at L, raising it through one inch, will be 

 suflBcient to evoke a large force at H sufficient to raise a heavy mass 

 through the same distance. Thus a force of 1 lb. moving through 

 one inch at L may result in a force of 1000 lbs. moving through one 

 inch at H. It is thus a work- (or power-) amphfier. 



So far it has given merely a simple and clear exemplification of the 

 principles of regulation and control described earlier. Later 

 (S.14/1) we shall return to it, for we shall have to be clear about how 

 we can have, simultaneously, a law saying that energy cannot be 

 created, and also a powev-aniplifier. 



Ex. 1 : How many degrees of freedom for movement have the three bodies, 

 P,J, G? 



Ex. 2: Modify the arrangement so as to make H move oppositely to L while 

 keeping the equilibrium stable. 



Ex. 3 : Modify the arrangement so that the equilibrium is unstable. 



GAMES AND STRATEGIES 



12/22. The subjects of regulation and control are extremely 

 extensive, and what has been said so far only begins to open up the 

 subject. Another large branch of the subject arises when D and R 

 are vectors, and when the compounding that leads eventually to 

 the outcome in T or £■ is so distributed in time that the components 

 of D and R occur alternately. In this case the whole disturbance 

 presented and the whole response evoked each consists of a sequence 

 of sub-disturbances and sub-responses. 



240 



