THE MULTISTABLE SYSTEM 



16/5 



The process can be illustrated on the homeostat. Tliree units 

 were connected so that the diagram of immediate effects was 

 2 ^± 1 ^±: 3 (corresponding to A, B, and C respectively). To 

 separate the effects of 2 and 3 on 1, bars were placed across the 

 potentiometer dishes (Figure 8/8/2) of 2 and 3 so that they could 

 move only in the direction recorded as downwards in Figure 

 16/5/1, while 1 could move either upwards or downwards. 

 If 1 was above the central line (shown broken), 1 and 2 inter- 

 acted, and 3 was independent ; but if 1 was below the central 

 line, then 1 and 3 interacted, and 2 was independent. 1 was 



u jVl ^ m * n 



—\j — \r 



v 



Time 



Figure 16/5/1 : Three units of the homeostat interacting. Bars in the 

 central positions prevent 2 and 3 from moving in the direction corre- 

 sponding here to upwards. Vertical strokes on U record changes of 

 uniselector position in unit 1. 



set to act on 2 negatively and on 3 positively, while the effects 

 2 — >- 1 and 3 — > 1 were uniselector-controlled. 



When switched on, at J, 1 and 2 formed an unstable system 

 and the critical state was transgressed. The next uniselector 

 connections (K) made 1 and 2 stable, but 1 and 3 were unstable. 

 This led to the next position (L) where 1 and 3 were stable but 

 1 and 2 became again unstable. The next position (M) did 

 not remedy this ; but the following position (N) happened to 

 provide connections which made both systems stable. The values 

 of the step-functions are now permanent ; 1 can interact repeatedly 

 with both 2 and 3 without loss of stability. 



It has already been noticed that if A, B and C should form 

 from time to time a triple combination, then the step-functions 



175 



