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Digital Subscriber System No. 1
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<p>Digital Subscriber Signalling System No. 1 (DSS1) is a <a href="/facts/Digital_data/JChckAvr">digital</a> signalling protocol (D channel protocol) used for the <a href="/facts/Integrated_Services_Digital_Network/zcV99rUb">ISDN</a>. It is defined by ITU-T I.411 (ETS 300 102). It supports <a href="/facts/Bearer_Capability/jacrNgk3">Bearer Capability</a>, Low Level Compatibility and High Level Compatibility, ANI, DNIS and redirected number signaling in both directions. A standard developed by <a href="/facts/ETSI/8rJbbhPg">ETSI</a> for <a href="/facts/Europe/DTAtrKfh">Europe</a> is known as Euro-ISDN or E-DSS1 or simply EDSS1 (European DSS1). </p><p>DSS1/EDSS1 protocol, in contrast, for example, to the protocol <a href="/facts/QSIG/cAtvwyGJ">QSIG</a>, was designed for use as access to public <a href="/facts/Integrated_Services_Digital_Network/zcV99rUb">ISDN</a> and asymmetric in the sense that it suggests a link with the network side at one end (digital <a href="/facts/Telephone_exchange/PaRpGm8I">public telephone exchange</a>) and the user (<a href="/facts/Private_branch_exchange/eLWvlhzs">private branch exchange</a> (PBX)) - at the other. </p><p>Since the market for ISDN equipment was open, ETSI provided guidance to suppliers of ISDN equipment by means of the minimum requirements for inter-connectivity to ISDN networks. These documents, called NET3 for <a href="/facts/Basic_rate_interface/JAynT4Td">BRI</a> and NET5 for <a href="/facts/Primary_rate_interface/tNSdVs55">PRI</a> lines, described a set of protocol tests terminals should comply to. Later, testing institutes, like <a href="/facts/KEMA/8EGK70nE">KEMA</a> in the Netherlands, implemented and performed the protocol tests and provided the appropriate certificates. </p><p>In 1989, 26 network operators from 20 European countries decided to develop EDSS1 as a pan-<a href="/facts/Europe/DTAtrKfh">European</a> standard to replace earlier national protocols (such as <a href="/facts/FTZ_1_TR_6/mWp0g4Wy">FTZ 1 TR 6</a> (Germany) or VN3 (France)). EDSS1 has been one of the keys to the success of the <a href="/facts/Integrated_Services_Digital_Network/zcV99rUb">ISDN</a> within European countries (as compared to, for example, the <a href="/facts/United_States/P0sCdLe5">U.S.</a>). </p><p>Non-European countries using DSS1 include <a href="/facts/Australia/qLHpbppq">Australia</a>, <a href="/facts/Brazil/QHkG46GL">Brazil</a>, <a href="/facts/Iran/24yukge8">Iran</a>, <a href="/facts/India/1kKHcnxM">India</a>, <a href="/facts/Israel/dEe3IcaY">Israel</a>, <a href="/facts/New_Zealand/4mpSlJdg">New Zealand</a>, <a href="/facts/Pakistan/cbIsvJy1">Pakistan</a>, <a href="/facts/Peru/dBt7XrYD">Peru</a>, <a href="/facts/Singapore/CQDkhUvD">Singapore</a>, <a href="/facts/South_Africa/vvXQpLgq">South Africa</a>, <a href="/facts/Sri_Lanka/VtTBmysE">Sri Lanka</a>, <a href="/facts/Taiwan/VcJoUD8w">Taiwan</a>, <a href="/facts/State_of_Palestine/WWcc0vRx">Palestine</a>, <a href="/facts/Mexico/IT5bwhdh">Mexico</a>, and the <a href="/facts/United_Arab_Emirates/o1bEjgbR">United Arab Emirates</a>. </p><p>The DSS1 protocol knows four different codesets for information elements. Codeset 0 regards to <a href="/facts/Q.931/CrX6l6gV">Q.931</a>, Codeset 5 to the ETSI standard, Codeset 6 for national applications and Codeset 7 for PBX applications. The most common Codeset is 0/Q.931. </p>