Digital Access Signalling System 1: Difference between revisions

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{{short description|Proprietary protocol providing ISDN services}}

'''Digital Access Signaling System 1''' ('''DASS1''') is a [[protocol (computing)|protocol]] defined by [[British Telecom]] for digital links to [[PSTN]] based on [[Integrated Services Digital Network|ISDN]].

{{Use dmy dates|date=April 2022}}

{{Ref improve|date=February 2024}}

'''Digital Access Signalling System 1''' ('''DASS1''') is a [[proprietary protocol]] defined by [[British Telecom]] to provide [[Integrated Services Digital Network|ISDN]] services in the [[United Kingdom]].<ref>{{cite web |title=Introduction To Line Telecommunications |url=https://www.tlc-direct.co.uk/Technical/Telecoms/History/TH022.htm |publisher=TLC |access-date=3 February 2024}}</ref> It is now obsolete, having been replaced by [[DASS2]]. This too will become obsolete over the coming years as [[Q.931]], a European standard, becomes widely adopted in the [[European Union|EU]].

==External links==

* [http://www.linkbit.com/support-decoder.html Linkbit Online DASS1 Message Decoder]

==References==

DASS2 is a superset of DPNSS which expands its capability to route calls across the PSTN and not just PABX to PABX.

{{Reflist}}

{{BT Group}}

[[Category:BT Group]]

It is defined in BTNR190 however it is very difficult to get a copy of this document.

[[Category:History of telecommunications in the United Kingdom]]

[[Category:Integrated Services Digital Network]]

Much of the data in DASS2 is compatible with DPNSS. For basic calls, only the header information changes.

{{techUK-stub}}

While developing a generic ISDN interface board, many sources suggested the DASS2 and DPNSS protocols are almost the same as EuroISDN. Extracting data from various ISDN types showed that the similarity ends with layer 2.

{{telecomm-stub}}

Signalling data is in timeslot 16. There are only 8 bits in each timeslot so a complete data message is built up from many frames. Messages are separated by a flag (01111110b).

This is a legacy ISDN standard and all new installations are EuroISDN/ISDN30e. Pete Garner, BSc.

==See also==

* [[DASS2]]

{{tech-stub}}

[[Category:Integrated Services Digital Network]]