> For the complete documentation index, see [llms.txt](https://prosbcdocs.telcobridges.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://prosbcdocs.telcobridges.com/telecom-references/protocols/isdn-specification.md).

# ISDN Specification

The ISDN protocol layer conforms to the following standards:

* ITU-T Q.920
* ITU-T Q.921
* ITU-T Q.931
* ETS 300 102
* ETS 300 125
* ETS 300 403-1, 403-2, 403-3
* AT\&T TR 41459
* TS-013 and TS-014

TelcoBridges' implementation of ISDN supports the following switch variants:

* Q.921 LAPD
* Q.931 ISDN PRI
  * NI-2
  * Lucent 4ESS
  * Lucent 5ESS
  * Nortel DMS-100
  * Nortel DMS-250
  * Euro ISDN ETSI NET5 (French, German, UK, China, Hong-Kong, and Korea)
  * Euro Numeris (VN6)
  * Japanese NTT INS-NET1500
  * Australian


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