Digital Access Signalling System 1
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Digital Access Signalling System 1 (DASS1) is a proprietary protocol defined by British Telecom to provide ISDN services in the United Kingdom.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</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 It is now obsolete, having been replaced by DASS2.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 EU.