Plate 2 



These photos symbolize three stages in the adv^ance of control systems. Left: This 

 steam-engine governor, photographed in motion at the Science Museum, London, is one of 

 the earliest examples of a practical automatic control system. Using the engine's output 

 (speed) to control the energy input to the engine, it foreshadows the use of the feedback, 

 so fundamental to modern control systems and to cybernetics (photo: Patrick Thurston). 

 Above: A modern test vehicle used for guidance and control experiments — sensing device 

 is at left, control devices at right. Much of the remaining space is taken up by calculating 

 devices — it is this stage of control that has developed so remarkably in modern s\-stems 

 (Crown Copyright). Right: A look into the future of control systems. Picture shows an 

 experimental arrangement enabling an automaton to change its own pattern of connec- 

 tions. Vertical tubes are filled with electrolyte and serve also as "bus bars." Insulating 

 film of oxide can be formed electrolytically on horizontal wires at points of intersection by 

 currents passed through them, thus altering input-output relations of the network so as to 

 match changing patterns of demand (MacKay and Ainsworth, Brit. Pat. App. 12887/61)- 



