ISDN service identifier

from Wikipedia, the free encyclopedia

An ISDN service identifier (English service indicator , SI ) allows the distinction between different services in an ISDN connection.

Different types of data can be transmitted over ISDN. The service identifier can be used to distinguish between these various services so that only a compatible terminal device can receive the connection .

In order for this concept to work, the caller must have set the appropriate service identifier for his terminal. If analog terminal devices ( telephone or fax ) are connected via converter , this is not always possible, since simple converters often do not support service IDs, the service ID is incorrectly set or all analog connections are provided with the same service ID. So that connections with such callers can still be established, the analog ports of the called party are set so that they accept all analog connections. However, an automatic differentiation between, for example, a telephone call and a fax on the basis of the service identifier is then no longer possible.

SI (Service Indicator) Service title
0x00 analog speech (3.1 kHz)
0x01 digital language
0x02 analog fax (G2 or G3)
0x03 digital data ( X.21 )
0x04 digital fax (G4)
0x05 digital data ( V.110 )
0x07 digital data ( X.75 )
0x08 digital data ( X.25 )
0x09 Teletex
0x0A Mixed mode
0x0D Telemetry data
0x10 digital videophone


  • Peter Bocker: ISDN - the integrated services digital message network. Third edition, Springer Verlag, Berlin / Heidelberg, ISBN 978-3-662-08031-3 .
  • Otfried Georg: Telecommunication technology . A practical introduction, Springer Verlag, Berlin / Heidelberg 1996, ISBN 978-3-540-61381-7 .
  • Jörg Fischer, Christian Sailer: VoIP Practical Guide. Carl Hanser Verlag, Munich 2016, ISBN 978-3-446-44491-1 .
  • Martin Werner: Networks, protocols, interfaces and communication. 1st edition, Friedrich Vieweg & Sohn Verlag, Braunschweig 2005, ISBN 3-528-03998-1 .

Web links