THE ERROR-CONTROLLED REGULATOR 



12/21 



to one end of a light stiff rod/, which can turn on a pivot K. Thus 

 if K is unmoving, a movement down at the other end L will lift the 

 cone, will allow air to escape, and will cause a fall of the pressure 

 z inside B; conversely, a movement up at L will make - rise. 



The air pressure in B works in opposition to a heavy weight P, 

 which is continued upwards as a pillar, the whole weight being 

 able to move only up or down. The pillar carries two pivots, K and 



Fig. 12/21/1 



M. M is pivot for a strong bar G, which is fixed at one end, F. 

 Thus if P moves upwards, M must move upwards by the same 

 amount, and G's free end H must move upwards by twice the distance. 

 Now let us see what happens if L is moved. Suppose the operator 

 lifts L by one inch. The other end (K) falls at once by one inch, 

 the valve is more obstructed, less air escapes, and more accumulates 

 in B, sending up the pressure. The increased pressure will lift /*, and 

 thus M and H. Thus H's movements tend simply to copy Us. (We 

 can notice that the upward movement of P (L being fixed after its 

 one inch rise) will make the valve V open, so the response of the 

 whole system to L's movement will be self-limiting, for the feedback 

 is negative; subject to certain quantitative details, which would 



239 



