14 
V.1 Systems with uni-directional communication 
1.1 Single systems (serial) 
Such systems have a serial arrangement of the analogue and digital 
components. Therefore their configurations are relatively simple. Figure 5a 
shows a block diagram of a single serial system without a digital computer, 
whereas figure 5b represents a similar system with a digital computer incor- 
porated. 
| Plotting Conventional Dig. Recording € e 
| Device vi Instrument nteriace Device 
Keyboard Drafting | 
O-no. display {Machine | 
  
  
  
  
  
  
  
  
  
  
  
  
figure Sa 
single serial system without computer 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
| Plotting Conventional Digital 
; ; 
| Device Instrument Interface Computer JO units 
He gunna | | : + ]4 3 I 
—— | 
Keyboard | “Drafting = 5. | | 
@-no. display | Machine | mnl ev 
——-—-— (Graphic CRT! 
| Display | 
| Terminal | 
vom eme d a À 
figure 5b 
single serial system with computer € ® 
In both cases the interactions between analogue and digital components 
are limited. However, the number of parameters involved in information flow, 
its rate, and the complexity of processing and control may differ substantially 
in the alternative approaches. 
Systems without a computer (figure 5a) represent the simplest version. 
The flow of information from instrument to interface is restricted to model 
co-ordinates and orientation parameters. The interface is equipped e.g.