FTZ 1 TR 6

FTZ 1 TR 6 (or 1 TR 6) is the standard for the obsolete German national digital signalling protocol (D channel protocol)[1] used for the ISDN. The standard was originally released in November 1990.[2] It has been superseded by DSS1[3] but is still in use on some lines and private exchanges.

1 TR 6 did not support multiple subscriber numbers but featured an Endgeräteauswahlziffer (EAZ, German "user device selection digit"). ISDN subscribers would get a sequence of 10 subsequent subscriber numbers, the last digit of which being the EAZ. The EAZ "0" was used for "global calls" to all connected devices.

1 TR 6 also offered semipermanent connections, which were (comparatively cheap) leased lines that could be temporarily disabled to use the B channel for other purposes.

It is said that the "TR" simply stands for "technische Richtlinie" (technical guidelines).

References

  1. ^ Abkürzungen zum Fach Kommunikationssysteme [Abbreviations for the subject of communication systems] (PDF) (Report) (in German). Rostock: Institut für Nachrichtentechnik und Informationselektronik, Fachbereich Elektrotechnik und Informationstechnik, Rostock University. 1999. Retrieved 29 November 2025.
  2. ^ ISDN Message Set (1TR6_NSA) Reference Manual (PDF) (Report). Vol. 8. IDACOM Electronics. 1990.
  3. ^ Klaß, Christian (24 June 2005). "Totgesagte leben länger: ISDN-Anschlüsse mit 1TR6" [Reports of its death have been greatly exaggerated: ISDN connections with 1TR6]. Golem magazine (in German). Retrieved 29 November 2025.
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