17 
digital recording units. A software package, including the basic and application 
programmes, is available. 
Kern DC-2 Interacting Digitiser-Graphic System (22) comprises the DC-2 
interface unit, a photogrammetric plotter (e.g. PG2). a table-top calculator 
(Hewlett Packard series), a digital recording device and/or an automatic 
drafting machine (AT). As in other systems, a control panel, display unit and 
teletype are provided. The basic and some application software is available. 
The Zeiss Jena modular system (17) is identical to that with the Coordi- 
meter F, with the difference that the latter is replaced by the KRS 4100 
computer. 
1.2 Multiple systems (serial) 
A significant development has been the implementation of the multiple 
system concept. In a multiple system several single serial systems (i.e. sub- 
systems) are linked to a central computer. 
For certain applications the individual (sub-) systems operate indepen- 
dently and thus unrelated. In other applications their operation can be synchro- 
nised by the central computer. Multiple systems use common peripheral units 
(linked to the central computer). The central computer may be a more power- 
ful minicomputer. It receives raw data from the individual (sub-) systems on 
time sharing basis. These data should often be conditioned, i.e. converted into 
a more useful form. After appropriate processing the data of different (sub-) 
systems can be recorded on separate media. Multiple systems are feasible 
for bulk-production, particularly of uniform products. 
The information flow between the individual (sub-) systems and the 
central computer can be uni- or bi-directional. Accordingly a distinction can 
be made between: 
— simple multiple systems, 
— multiple systems with a distributive computer network. 
The configurations of the two versions are represented in figures 6a 
and 6b.