Tial state (discussed in S.11/19) is really included in the cases
Mentioned above. Such a difficulty occurs to a railway signalman
In a fog. He is well informed that a disturbance “fog” has arrived,
But he often has difficulty in ascertaining the present state of the
System he is controlling, i.e. the present positions of the trains in
His sector. With this restriction in the flow of information from T
To R goes the difficulty, or even impossibility, of maintaining full
Regulation.
The basic formulation of S.11/4 assumed that the process of
Regulation went through its successive stages in the following order:
A particular disturbance threatens at D;
It acts on R, which transforms it to a response;
The two values, of D and R, act on T simultaneously to pro-
Duce T’s outcome;
The outcome is a state in E, or affects E.
Thus (3) supposes that if R is an actual material system, it performs
All its work before T starts to move. We assumed, in other words
That the regulator R moved at a higher order of speed than T.
This sequence does actually occur in many cases. When the cat
Approaches, the mouse may react so as to get to its hole before the
Cat’s claws actually strike. We say in general that the organism
Has reacted to the threat (at D) rather than to the disaster itself (at
E), and has thus forestalled the disaster. The formulation is thus
Properly representative of many important regulations.
On the other hand, there are many important cases in which this
Anticipation is not possible— in which R’s action cannot be com-
Pleted before the outcome (at T) starts to be determined. (An
Example is given in the next section.) In such cases the regulation
Envisaged in S.11/3 is impossible. What then is to be done?
One method, of course, is to speed up the transmission of infor-
Mation from D to R; and many regulating systems have various
Devices specially to this end. Primitive nerve fibres develop mye-
Lin sheaths, so that the passage to the brain may be faster. Some
Organisms develop a sense of smell, so that the appropriate
221
A N I N T R O D UC T I O N T O C Y B E R NE T I C S
TH E ERR O R- CO N TR O LLED REG U LA TO R
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Response may be prepared in time for the actual bodily encounter.
And economic systems send messages by cable rather than by
Messenger so that the arrival in port of a ship with a perishable
Cargo can be prepared for.
Sometimes, however, the available resources do not include a
Speeding-up of the transmission through R; R’s reaction cannot be
Got to T before the outcome commences. In that case, the best that
Can be done is that the imperfect regulation should at least be as
Good as it can be made in the circumstances. The succeeding sec-
Tions will discuss how this can be done.
Regulation by error. A well-known regulator that cannot react
Directly to the original disturbance D is the thermostat controlled
Water- bath, which is unable to say “I see someone coming with a
Cold flask that is to be immersed in me— I must act now”. On the
Contrary, the regulator gets no information about the disturbance
Until the temperature of the water (E) actually begins to drop. And
The same limitation applies to the other possible disturbances, such
As the approach of a patch of sunlight that will warm it, or the leav-
Ing open of a door that will bring a draught to cool it.
The same limitation holds over many important regulators.
There is, for instance, a mechanism that helps to keep constant the
Oxygen supply to the tissues: any long-continued lack of oxygen
Causes eventually an increase in the number of red corpuscles
Contained in the blood. So people with certain types of heart dis-
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