It proved to be necessary to introduce another (serial) 
interface for the connection of the instrument to digital 
computers. Thus the DZT 90 x 120 can also accept data in 
on-line operation from a computer (Fig. 2). The internal 
instruction volume of the DZT allows the following functions: 
. writing of point numbers 
. writing of terrain heights 
. straight-line connections (10 line types) 
. drawing of 10 basic symbols and its combination in 3 sizes 
In the program system TOPAS a program package CONT is offered 
tor the DZT 90 x 120 which with any given arrangement of 
points in a digital height model provides the drawing instruc- 
tions for drawing a contour plan. The DZT 90 x 120 incorpos 
rates part of the functions of the digitizer interface, which 
are necessary for the on-line connection to a measuring in- 
strument. If such a connection is not required, the internal 
intelligence of the instrument can essentially be enhanced. 
The DZT 90 x 120/RS was therefore designed as a peripheral 
instrument for digital computers and the instruction format 
and instruction volume were considerably changed. Coupling 
with the computer is again made via a serial interface, 
There are altogether 27 drawing instructions for the DZT 
90 x 120/RS, which inter alia enable the following functions: 
. Positioning, choice of tools 
. Straight-line connection with different line types 
. Drawing of symbols and ASCII characters of any size and in 
any direction 
. Circle interpolation (including circular arcs) 
. Mirror image representations on arbitrary straight lines 
. Input of view port coordinates 
. Transfer of drawing table coordinates and error status 
into the connected computer 
The computer-assisted DZT 90 x 120/RGS stereoplotting system 
represents the upgraded design. This system is fitted with a 
programmable digital computer with 2 disk drives, which allows 
different calculations with measurement series (absolute 
orientation, drawing table orientation, recording, mapping). 
For example, in the mapping program the rectangularity and 
parallelism of & building can be generated and & hachure 
added. This system is part of a concept for the decentralized 
computer application. A connection to a mainframe computer 
can be established by a magnetic tape unit (off-line). 
The use of the diskettes enables the range of internal func- 
tions being possible within the system to be permanently 
extended. 
At the moment three program diskettes are available: 
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