ISDN Specifications¶

Unfortunately there are many dialects of ISDN. This was common-place in the old national PSTN networks even before ISDN, so it seemed "normal" at the time.

International / ITU-T (formerly known as CCITT)¶

• Q.921 (LAPD)
• Q.931 (Call Control)

Europe / ETSI¶

Etsi specified what was later known as "Euro-ISDN".

• EN 300 403-1 (DSS1 Part 1: Protocol Specification)
• EN 300 403-2 (DSS1 Part 2: SDL Diagrams)

Germany¶

In Germany, there was a national ISDN dialect called 1TR6, which was later obsoleted by Euro-ISDN. See German_FTZ_ISDN_Specifications.

Further wiki pages¶

• German FTZ ISDN Specifications
• V110
• V120
• X31
• X75