FTZ 1 TR 6

This article does not cite any sources. Please help by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources:  –  ·  ·  · scholar · JSTOR (December 2009) (Learn how and when to remove this template message)

FTZ 1 TR 6 (or 1 TR 6) is the standard for the obsolete German national digital signalling protocol (D channel protocol) used for the ISDN. It has been superseded by DSS1 but is still in use on some lines and private exchanges.

1 TR 6 did not support 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).

External links[]

• Scanned FTZ 1 TR 6 specifications, published in Osmocom retronetworking wiki. (list), Osmocom.