15 
with hardwired circuits for the basic control functions (i.e. acquisition, 
transfer and recording) and sometimes for simple processing. 
The digital components available at present, belonging to this class, are 
Dell Foster RSS 400, Keuffel & Esser Ecars, Auto-Trol M 3700, Wild EK-22, 
Zeiss Oberkochen Ecomat 11, DIREC 1 and DZ-5, Kern ER-2, DC-2 and . 
PG-2-AT system, Zeiss Jena Co-ordimeter F, Matra/SFOM short system, 
Galileo Rec III and others. The properties (i.e. flexibility, versatility, compa- 
tibility, performance and reliability) of these systems differ considerably. 
All, except PG-2-AT and DZ-5, are suitable for recording data in digi- 
tal form. Most of the listed equipment is compatible with different types of 
photogrammetric instruments computers, and recording devices. The majority 
can operate in stationary, time-controlled, distance controlled mode, or in 
combinations thereoff. They have different capacities and flexibility with 
regard to output format, number of parameters (three or four), number of 
digits per parameter, arrangement of fields for additional data, displays, re- 
and pre-setting facilities, processing facilities, etc. 
Zeiss Jena has developed attachable modules for digital profiling with 
the Topocart (with or without Orthophot C) and the Stereometrograph (17). 
These modules are: electrical motor drive (e.g. for the Y-screw), a digitiser 
box (with synchro receivers and digitisers for X, Y, Z), Co-ordimeter F, and 
a paper tape punch. When linked to Topocart an adapter box, distributing 
gears and a power supply unit must be added. If Topocart operates with 
the Orthophot C, the extra motor drive with power supply unit is not needed. 
A system for graphical recording via a digital interface is the Kern 
PG2-AT (Automatic Table). The interface is a hardwired microprocessor 
linking a PG2 plotter, via encoders and stepping motors, with a tiltable auto- 
matic drawing table AT (of Data Technology, Boston). The system has several 
important merits, i.e. a bulk-storage is not needed (due to on-line operation). 
The software is relatively simple. It provides for high accuracy and speed, 
permits one-man operation, gives possibility for separate scaling in X and Y, 
provides for interchangeability of the axes, enables automatic plotting of 
straight line segments, point- and line symbols, and automatic manuscript 
preparation, etc. 
Another system for graphical recording has been developed by Zeiss 
Oberkochen. The system comprises a photogrammetric plotter (e.g. Planimat,