Integrated text and data network
The integrated text and data network ( IDN ), also known as the "integrated telex and data network", was a data network that was introduced in the Federal Republic of Germany in 1975 . It was based on the electronic switching system EDS, which Siemens AG supplied to the Deutsche Bundespost . Until then, the various telecommunications networks for each service were made up of special transmission and switching devices and components, but a digital telecommunications network has now been set up to transport several services. The following networks have been combined in the IDN:
- the telex network for the telegraphy service (from 1981)
- the Gentex network, which was an internal network of the postal administrations for the transmission of telegrams
- the direct call network , which provided dedicated lines, at that time with a maximum of 9600 bit / s
- the Datex-L network for circuit-switched digital dial-up connections
- the Datex-P network for packet-switched dial - up connections (from 1980)
The IDN provided a central step file for these services. Because all sending and receiving stations of these services used this central clock for bit synchronization, their synchronization was guaranteed and conversions between them were possible. The central step act was a prerequisite for the integration of the services.
The line-technical requirement for the IDN was provided by the telephone network . The long -haul routes of the upper network level, which represented the data network between the individual EDS switching systems, were implemented with 2 Mbit / s multiplex routes, the basic bit rate E1 of the PDH hierarchy. Time division multiplex systems for data transmission, so-called ZD systems, combine the different transmission speeds of the individual connections to form a 2 Mbit / s signal. The connection of data terminal equipment was carried out via data transmission equipment , which mainly worked according to the baseband method . The IDN expanded the telex network to include services such as speed dialing , direct calling , subscriber operating class , circulars , notification and the addition of date and time . When the teletex service came up, the IDN was expanded to include telex / teletex converters (from 1981) so that the modern memory typewriters of the teletex service, which were already equipped with screens, could exchange messages with teleprinters and their paper tape.
When the Deutsche Bundespost officially put ISDN into operation in 1989 , the IDN quickly lost its importance.
Deutsche Telekom (Hrsg.): The historical development of switching devices for telephone and data communication from 1945 onwards - an overview - A piece of technology history , in instruction sheets: the specialist journal of Deutsche Telekom for training and further education, Volume 57-2, Hamburg 2004 , Pp. 88-101