-8 . 
INTERNATIONAL SOCIETY FOR PHOTOGRAMMETRY AND REMOTE SENSING 
Commission VI 
Symposium held in Mainz, FR Germany, 22 - 25 September 1982 
  
DATA COMMUNICATION OVER 
PUBLIC NETWORKS 
Walter Tietz 
Fernmeldetechnisches Zentralamt, Darmstadt, FR Germany 
ABS TRACT 
Data connection between interfaces and their compatibility is outlined. Open 
communication systems are stressed. Access to telecommunication networks is 
mentioned. Users rely on the performance capability and on the error control 
system of countries being involved in the data transport. As an example for 
international connections, the situation in the FR Germany is delineated. 
1. Types of services and general aspects 
All telecommunication services are used to transmit electric signals. The cha- 
racteristic feature of data communication services is that they are based on 
communication networks which use interfaces defined for the data signals and have 
the task of transporting these signals between interfaces. The data sources and 
sinks also termed data terminal equipment (DTE) operate over the communication 
network, the inner structure of which may be technically different. Data con- 
nections between the interfaces may be 
- permanently dedicated or 
- provided temporarily, that is switched 
Figure 1 shows the interdependence of the system components in a data communication 
system which , in general terms, is also called teleprocessing system. 
All types of data communication performed over public telecommunication networks 
in the Federal Republic of Germany are called Datel services whose function is the 
transport of data. These data communication services differ in the various coun- 
tries in their legal provisions, technical characteristics and certain facilities. 
M — Data Network 
| Fr DatacOMMuMENtION Net work 
Ver ME Station messe un 
| Reftected 
Datostation \ image 
  
OTE DCE 
  
  
  
| 
Switching Network 
| Access Line 
I fransms sion Nelwork - bam 
I 
| 
i 
  
  
  
  
  
  
Transport Network 
  
  
  
  
  
  
  
  
digital _ann Loy - analogue o, d'a! 
signais | signals signals 
Interfuce between OTE and DCE 
Packet - switched. Stations x 25 
Circus - switched Stations X 20/X 20bıs 
X 21/X 21bıs 
DCE on Tetepnone Stations V - (mterfacen 
DCE on Fixed Connections V-[nterfacon or X - [nterfaces 
OTE: Dota Terminal Equipment 
DCE. Data Circuit - terminating Equipment 
Figure | Interface between OTE and OCE and essential network components 
Bibliograpnic quotation : 
Tietz, W. : Data communication over public networks. In: Int. Archive of Photo- 
grammetry, 24 -VI, pp 78 - 81, Mainz 1982