19 
   
  
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
iiem 
IPlotting Conventional 
j Device Instrument 2 
EE T @-no. Display 
Keyboard 1 
ee = té Microcomputer 2 . u 
IPlotting Conventional 
|Device Instrument 2 ^" Mini Input/Output 
IR = {Computer Units 
@-no. Display 
Keyboard 2 um i: Ho a 
a YT rus p | [Graphic CRT | 
— — *- ^A |Display Terminal(s) | 
Microcomputer n 
IPlotting Conventional 
Device Instrument n 
  
  
  
  
  
  
O-no. Display 
Keyboard n 
  
  
  
figure 6b 
multiple system with distributive computer network (serial) 
V.2 Systems with bi-directional communication 
The information flow between analogue and digital components is, in 
this case, bi-directional. This, however, permits high level interactions 
between the components, which further increases flexibility, versatility and 
performance. : 
Operation of such systems may depend on current outputs, which per- 
mits implementation of self-adaptive controls. Some decisions, which are 
normally taken by human operator, can be made by computer. 
Digital control can be applied to several instrumental parameters. Most 
commonly these are the model co-ordinates (X, Y, Z). However, in hybrid 
systems the photo-co-ordinates (x’, y’; x", y") or sometimes selected orien- 
tation parameters (particularly by) may also be controlled digitally. 
As in the class of serial systems (paragraph V.1), a distinction can be