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| first_published = {{End date and age|1988}}{{Efn|There is not a single ISDN specification, | | first_published = {{End date and age|1988}}{{Efn|There is not a single ISDN specification, more a collection of various incompatible dialects.}} | ||
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[[File:ISDN telefono.jpg|thumb|ISDN telephone]] | [[File:ISDN telefono.jpg|thumb|ISDN telephone]] | ||
'''Integrated Services Digital Network''' ('''ISDN''') is a set of communication standards for simultaneous [[Digital data|digital]] [[Transmission (telecommunications)|transmission]] of voice, video, data, and other network services over the digitalised circuits of the [[public switched telephone network]].<ref>{{Cite book|last=Dr. rer. nat. Peter Bocker|title=ISDN The Integrated Services Digital Network: Concepts, Methods, Systems.|publisher=Springer Berlin Heidelberg|year=1988|isbn=978-3-662-08036-8}}</ref> Work on the standard began in 1980 at [[Bell Labs]] and was formally standardized in 1988 in the [[ITU-T|CCITT]] "Red Book".<ref>{{cite journal|journal=IEEE Journal on Selected Areas in Communications|date=May 1986|volume= 4|issue= 3|pages = 320–25 | issn= 0733-8716|doi= 10.1109/JSAC.1986.1146333| title= CCITT Recommendations on the ISDN: A Review | last1 = Decina| first1= M |last2= Scace| first2= E}}</ref> By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market. One estimate suggests ISDN use peaked at a worldwide total of 25 million subscribers at a time when 1.3 billion analog lines were in use.{{sfn|Cioffi|2011|p=30}} ISDN has largely been replaced with [[digital subscriber line]] (DSL) systems of much higher performance. | '''Integrated Services Digital Network''' ('''ISDN''') is a set of communication standards for simultaneous [[Digital data|digital]] [[Transmission (telecommunications)|transmission]] of voice, video, data, and other network services over the digitalised circuits of the [[public switched telephone network]].<ref>{{Cite book|last=Dr. rer. nat. Peter Bocker|title=ISDN The Integrated Services Digital Network: Concepts, Methods, Systems.|publisher=[[Springer Berlin]] Heidelberg|year=1988|isbn=978-3-662-08036-8}}</ref> Work on the standard began in 1980 at [[Bell Labs]] and was formally standardized in 1988 in the [[ITU-T|CCITT]] "Red Book".<ref>{{cite journal|journal=[[IEEE Journal on Selected Areas in Communications]]|date=May 1986|volume= 4|issue= 3|pages = 320–25 | issn= 0733-8716|doi= 10.1109/JSAC.1986.1146333| title= CCITT Recommendations on the ISDN: A Review | last1 = Decina| first1= M |last2= Scace| first2= E |bibcode=1986IJSAC...4..320D }}</ref> By the time the standard was released, newer networking systems with much greater speeds were available, and ISDN saw relatively little uptake in the wider market. One estimate suggests ISDN use peaked at a worldwide total of 25 million subscribers at a time when 1.3 billion analog lines were in use.{{sfn|Cioffi|2011|p=30}} ISDN has largely been replaced with [[digital subscriber line]] (DSL) systems of much higher performance. | ||
Prior to ISDN, the telephone system consisted of digital links like [[T-carrier|T1]]/[[E-carrier|E1]] on the long-distance lines between telephone company offices and analog signals on [[Twisted pair|copper telephone wires]] to the customers, the "[[Last mile (telecommunications)|last mile]]". At the time, the network was viewed as a way to transport voice, with some special services available for data using additional equipment like [[modem]]s or by providing a T1 on the customer's location. What became ISDN started as an effort to digitize the last mile, originally under the name "Public Switched Digital Capacity" (PSDC).{{sfn|Cioffi|2011|p=30}} This would allow call routing to be completed in an all-digital system, while also offering a separate data line. The [[Basic Rate Interface]], or BRI, is the standard last-mile connection in the ISDN system, offering two {{nowrap|64 kbit/s}} "bearer" lines and a single {{nowrap|16 kbit/s}} "data" channel for commands and data. | Prior to ISDN, the telephone system consisted of digital links like [[T-carrier|T1]]/[[E-carrier|E1]] on the long-distance lines between telephone company offices and analog signals on [[Twisted pair|copper telephone wires]] to the customers, the "[[Last mile (telecommunications)|last mile]]". At the time, the network was viewed as a way to transport voice, with some special services available for data using additional equipment like [[modem]]s or by providing a T1 on the customer's location. What became ISDN started as an effort to digitize the last mile, originally under the name "Public Switched Digital Capacity" (PSDC).{{sfn|Cioffi|2011|p=30}} This would allow call routing to be completed in an all-digital system, while also offering a separate data line. The [[Basic Rate Interface]], or BRI, is the standard last-mile connection in the ISDN system, offering two {{nowrap|64 kbit/s}} "bearer" lines and a single {{nowrap|16 kbit/s}} "data" channel for commands and data. | ||
ISDN remains successful globally, but in the US the system was largely ignored and garnered the industry nickname "innovation(s) subscribers didn't need."{{sfn|Cioffi|2011|p=31}} The underlying ISDN concepts found wider use as a replacement for the T1/E1 lines it was originally intended to extend, roughly doubling the performance of those lines. | |||
== History == | == History == | ||
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=== Standardization === | === Standardization === | ||
Around 1978, Ralph Wyndrum, Barry Bossick and Joe Lechleider of [[Bell Labs]] began one such effort to develop a last-mile solution. They studied a number of derivatives of the T1's AMI concept and concluded that a customer-side line could reliably carry about {{nowrap|160 kbit/s}} of data over a distance of {{convert|4|to|5|miles}}. That would be enough to carry two voice-quality lines at {{nowrap|64 kbit/s}} as well as a separate {{nowrap|16 kbit/s}} line for data. At the time, [[modem]]s were normally {{nowrap|300 bit/s}} and {{nowrap|1200 bit/s}} would not become common until the early 1980s and the {{nowrap|2400 bit/s}} standard would not be completed until 1984. In this market, {{nowrap|16 kbit/s}} represented a significant advance in performance in addition to being a separate channel that coexists with voice channels.{{sfn|Cioffi|2011|p=31}} | Around 1978, Ralph Wyndrum, Barry Bossick and Joe Lechleider of [[Bell Labs]] began one such effort to develop a last-mile solution. They studied a number of derivatives of the T1's AMI concept and concluded that a customer-side line could reliably carry about {{nowrap|160 kbit/s}} of data over a distance of {{convert|4|to|5|miles}}. That would be enough to carry two voice-quality lines at {{nowrap|64 kbit/s}} as well as a separate {{nowrap|16 kbit/s}} line for data. At the time, [[modem]]s that were normally {{nowrap|300 bit/s}} and {{nowrap|1200 bit/s}} would not become common until the early 1980s and the {{nowrap|2400 bit/s}} standard would not be completed until 1984. In this market, {{nowrap|16 kbit/s}} represented a significant advance in performance in addition to being a separate channel that coexists with voice channels.{{sfn|Cioffi|2011|p=31}} | ||
A key problem was that the customer might only have a single twisted pair line to the location of the handset, so the solution used in T1 with separate upstream and downstream connections was not universally available. With analog connections, the solution was to use [[echo cancellation]], but at the much higher bandwidth of the new concept, this would not be so simple. A debate broke out between teams worldwide about the best solution to this problem; some promoted newer versions of echo cancellation, while others preferred the "ping pong" concept where the direction of data would rapidly switch the line from send to receive at such a high rate it would not be noticeable to the user. [[John Cioffi]] had recently demonstrated echo cancellation would work at these speeds, and further suggested that they should consider moving directly to {{nowrap|1.5 Mbit/s}} performance using this concept. The suggestion was literally laughed off the table | A key problem was that the customer might only have a single twisted pair line to the location of the handset, so the solution used in T1 with separate upstream and downstream connections was not universally available. With analog connections, the solution was to use [[echo cancellation]], but at the much higher bandwidth of the new concept, this would not be so simple. A debate broke out between teams worldwide about the best solution to this problem; some promoted newer versions of echo cancellation, while others preferred the "ping pong" concept where the direction of data would rapidly switch the line from send to receive at such a high rate it would not be noticeable to the user. [[John Cioffi]] had recently demonstrated echo cancellation would work at these speeds, and further suggested that they should consider moving directly to {{nowrap|1.5 Mbit/s}} performance using this concept. The suggestion was literally laughed off the table and his boss told him to "sit down and shut up."{{sfn|Cioffi|2011|p=31}} But the echo cancellation concept that was taken up by Joe Lechleider eventually came to win the debate.{{sfn|Cioffi|2011|p=31}} | ||
Meanwhile, the debate over the encoding scheme itself was also ongoing. As the new standard was to be international, this was even more contentious as several regional digital standards had emerged in the 1960s and 70s and merging them was not going to be easy. To further confuse issues, in 1984 the [[Breakup of the Bell System|Bell System was broken up]] and the US center for development moved to the [[American National Standards Institute]] (ANSI) T1D1.3 committee. Thomas Starr of the newly formed [[Ameritech]] led this effort and eventually convinced the ANSI group to select the [[2B1Q]] standard proposed by Peter Adams of [[British Telecom]]. This standard used an 80 kHz base frequency and encoded two bits per baud to produce the {{nowrap|160 kbit/s}} base rate. Ultimately Japan selected a different standard, and Germany selected one with three levels instead of four, but all of these could interchange with the ANSI standard.{{sfn|Cioffi|2011|p=32}} | Meanwhile, the debate over the encoding scheme itself was also ongoing. As the new standard was to be international, this was even more contentious as several regional digital standards had emerged in the 1960s and 70s and merging them was not going to be easy. To further confuse issues, in 1984 the [[Breakup of the Bell System|Bell System was broken up]] and the US center for development moved to the [[American National Standards Institute]] (ANSI) T1D1.3 committee. Thomas Starr of the newly formed [[Ameritech]] led this effort and eventually convinced the ANSI group to select the [[2B1Q]] standard proposed by Peter Adams of [[British Telecom]]. This standard used an 80 kHz base frequency and encoded two bits per baud to produce the {{nowrap|160 kbit/s}} base rate. Ultimately Japan selected a different standard, and Germany selected one with three levels instead of four, but all of these could interchange with the ANSI standard.{{sfn|Cioffi|2011|p=32}} | ||
From an economic perspective, the [[European Commission]] sought to liberalize and regulate ISDN across the [[European Economic Community]].<ref>{{cite journal |first=Reinhard |last=Schulte-Braucks |title=Telecommunications Law and Policy in the European Community |volume=13 |journal=[[Fordham International Law Journal|Fordham Int'l L.J.]] |page=234 |date=1989 |url=https://ir.lawnet.fordham.edu/ilj/vol13/iss2/5 |issue=2 |access-date=2022-10-18}}</ref> The [[Council of the European Communities]] adopted Council Recommendation | From an economic perspective, the [[European Commission]] sought to liberalize and regulate ISDN across the [[European Economic Community]].<ref>{{cite journal |first=Reinhard |last=Schulte-Braucks |title=Telecommunications Law and Policy in the European Community |volume=13 |journal=[[Fordham International Law Journal|Fordham Int'l L.J.]] |page=234 |date=1989 |url=https://ir.lawnet.fordham.edu/ilj/vol13/iss2/5 |issue=2 |access-date=2022-10-18}}</ref> The [[Council of the European Communities]] adopted Council Recommendation<ref>{{Cite web |url=https://eur-lex.europa.eu/eli/reco/1986/659 |title=EUR-Lex - 31986H0659 - IT - EUR-Lex |access-date=2022-10-18 |archive-date=2022-10-18 |archive-url=https://web.archive.org/web/20221018042541/https://eur-lex.europa.eu/eli/reco/1986/659 |url-status=bot: unknown }}</ref> in December 1986 for its coordinated introduction within the framework of CEPT. [[ETSI]] (the European Telecommunications Standards Institute) was created by CEPT in 1988 and would develop the framework. | ||
=== Rollout === | === Rollout === | ||
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Lechleider also believed this higher-speed standard would be much more attractive to customers than ISDN had proven. Unfortunately, at these speeds, the systems suffered from a type of [[crosstalk]] known as "NEXT", for "near-end crosstalk". This made longer connections on customer lines difficult. Lechleider noted that NEXT only occurred when similar frequencies were being used, and could be diminished if one of the directions used a different carrier rate, but doing so would reduce the potential bandwidth of that channel. Lechleider suggested that most consumer use would be asymmetric anyway, and that providing a high-speed channel towards the user and a lower speed return would be suitable for many uses.{{sfn|Cioffi|2011|p=34}} | Lechleider also believed this higher-speed standard would be much more attractive to customers than ISDN had proven. Unfortunately, at these speeds, the systems suffered from a type of [[crosstalk]] known as "NEXT", for "near-end crosstalk". This made longer connections on customer lines difficult. Lechleider noted that NEXT only occurred when similar frequencies were being used, and could be diminished if one of the directions used a different carrier rate, but doing so would reduce the potential bandwidth of that channel. Lechleider suggested that most consumer use would be asymmetric anyway, and that providing a high-speed channel towards the user and a lower speed return would be suitable for many uses.{{sfn|Cioffi|2011|p=34}} | ||
This work in the early 1990s eventually led to the [[ADSL]] concept, which emerged in 1995. An early supporter of the concept was [[Alcatel]], who jumped on ADSL while many other companies were still devoted to ISDN. Krish Prabu stated that "Alcatel will have to invest one billion dollars in ADSL before it makes a profit, but it is worth it." They introduced the first DSL Access Multiplexers ([[DSLAM]]), the large multi-modem systems used at the telephony offices, and later introduced customer ADSL modems under the Thomson brand. [[Alcatel-Lucent|Alcatel]] remained the primary vendor of ADSL systems for well over a decade.{{sfn|Cioffi|2011|p=38}} | This work in the early 1990s eventually led to the [[ADSL]] concept, which emerged in 1995. An early supporter of the concept was [[Alcatel]], who jumped on ADSL while many other companies were still devoted to ISDN. Krish Prabu, COO of Alcatel, stated that "Alcatel will have to invest one billion dollars in ADSL before it makes a profit, but it is worth it." They introduced the first DSL Access Multiplexers ([[DSLAM]]), the large multi-modem systems used at the telephony offices, and later introduced customer ADSL modems under the Thomson brand. [[Alcatel-Lucent|Alcatel]] remained the primary vendor of ADSL systems for well over a decade.{{sfn|Cioffi|2011|p=38}} | ||
ADSL quickly replaced ISDN as the customer-facing solution for last-mile connectivity. ISDN has largely disappeared on the customer side, remaining in use only in niche roles like dedicated teleconferencing systems and similar legacy systems. | ADSL quickly replaced ISDN as the customer-facing solution for last-mile connectivity. ISDN has largely disappeared on the customer side, remaining in use only in niche roles like dedicated teleconferencing systems and similar legacy systems. In 2026, the ISDN subsystem within the [[Linux kernel]] was finally retired and removed. <ref>{{Cite web |last=Laranel |first=Michael |date=24 April 2026 |title=Farewell ISDN, Ham Radio & Old Network Drivers: Linus Torvalds Merges 138k L.O.C. Removal |url=https://www.phoronix.com/news/Linux-7.1-Removes-Old-Net |access-date=2026-04-25 |website=www.phoronix.com |language=en}}</ref> | ||
== Design == | == Design == | ||
''Integrated services'' refers to ISDN's ability to deliver at minimum two simultaneous connections, in any combination of data, voice, [[Videotelephony|video]], and [[fax]], over a [[local loop|single line]]. Multiple devices can be attached to the line, and used as needed. That means an ISDN line can take care of what were expected to be most people's complete communications needs (apart from [[broadband Internet access]] and entertainment [[television]]) at a much higher transmission rate, without forcing the purchase of multiple analog phone lines. It also refers to integrated switching and transmission<ref>{{Cite journal |title= Pragmatic Introduction of Digital Switching and Transmission in Existing Networks | first1= G | last1 = Robin | first2= S | last2 = Treves |journal= IEEE Transactions on Communications |date= July 1979 |volume=27 |doi=10.1109/TCOM.1979.1094494 |issue= 7 |page = 1071}}</ref> in that [[telephone switch]]ing and [[carrier wave]] transmission are integrated rather than separate as in earlier technology. | ''Integrated services'' refers to ISDN's ability to deliver at minimum two simultaneous connections, in any combination of data, voice, [[Videotelephony|video]], and [[fax]], over a [[local loop|single line]]. Multiple devices can be attached to the line, and used as needed. That means an ISDN line can take care of what were expected to be most people's complete communications needs (apart from [[broadband Internet access]] and entertainment [[television]]) at a much higher transmission rate, without forcing the purchase of multiple analog phone lines. It also refers to integrated switching and transmission<ref>{{Cite journal |title= Pragmatic Introduction of Digital Switching and Transmission in Existing Networks | first1= G | last1 = Robin | first2= S | last2 = Treves |journal= IEEE Transactions on Communications |date= July 1979 |volume=27 |doi=10.1109/TCOM.1979.1094494 |issue= 7 |page = 1071 | bibcode= 1979ITCom..27.1071R }}</ref> in that [[telephone switch]]ing and [[carrier wave]] transmission are integrated rather than separate as in earlier technology. | ||
=== Configurations === | === Configurations === | ||
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[[File:ISDN box on wall June 21.jpg|thumb|A decommissioned BT ISDN 2e box]] | [[File:ISDN box on wall June 21.jpg|thumb|A decommissioned BT ISDN 2e box]] | ||
The entry level interface to ISDN is the [[Basic Rate Interface]] (BRI), a 128 [[kilobits per second|kbit/s]] service delivered over a pair of standard telephone copper wires.<ref name="Talkers 2013-03-28"/> The {{nowrap|144 kbit/s}} overall payload rate is divided into two {{nowrap|64 kbit/s}} [[bearer channel]]s ([[B channel|'B' channels]]) and one {{nowrap|16 kbit/s}} signaling channel ([[D channel|'D' channel]] or data channel). This is sometimes referred to as 2B+D.<ref name="SW Bell ISDN">{{cite web|title=What is ISDN?|url=http://public.swbell.net/ISDN/overview.html|publisher=Southwestern Bell|access-date=April 6, 2013|archive-url=https://web.archive.org/web/20130415082843/http://public.swbell.net/ISDN/overview.html|archive-date=April 15, 2013|url-status=dead}}</ref> | The entry level interface to ISDN is the [[Basic Rate Interface]] (BRI), a 128 [[kilobits per second|kbit/s]] service delivered over a pair of standard telephone copper wires.<ref name="Talkers 2013-03-28">{{cite web|title=Verizon: No Longer Taking Orders for ISDN Service in Northeast Starting May 18|url=http://www.talkers.com/2013/03/28/verizon-no-longer-taking-orders-for-isdn-service-in-northeast-starting-may-18/|work=Talkers|access-date=April 6, 2013|date=March 28, 2013|archive-date=February 3, 2020|archive-url=https://web.archive.org/web/20200203105609/http://www.talkers.com/2013/03/28/verizon-no-longer-taking-orders-for-isdn-service-in-northeast-starting-may-18/|url-status=dead}}</ref> The {{nowrap|144 kbit/s}} overall payload rate is divided into two {{nowrap|64 kbit/s}} [[bearer channel]]s ([[B channel|'B' channels]]) and one {{nowrap|16 kbit/s}} signaling channel ([[D channel|'D' channel]] or data channel). This is sometimes referred to as 2B+D.<ref name="SW Bell ISDN">{{cite web|title=What is ISDN?|url=http://public.swbell.net/ISDN/overview.html|publisher=Southwestern Bell|access-date=April 6, 2013|archive-url=https://web.archive.org/web/20130415082843/http://public.swbell.net/ISDN/overview.html|archive-date=April 15, 2013|url-status=dead}}</ref> | ||
The interface specifies the following network interfaces: | The interface specifies the following network interfaces: | ||
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=== Telephone industry === | === Telephone industry === | ||
ISDN is a core technology in the telephone industry. A [[telephone network]] can be thought of as a collection of wires strung between switching systems. The common electrical specification for the signals on these wires is [[Digital Signal 1|T1]] or [[E-carrier|E1]]. Between telephone company switches, the signaling is performed via [[Signaling System No 7|SS7]]. Normally, a PBX is connected via a T1 with [[robbed bit signaling]] to indicate on-hook or off-hook conditions and [[ | ISDN is a core technology in the telephone industry. A [[telephone network]] can be thought of as a collection of wires strung between switching systems. The common electrical specification for the signals on these wires is [[Digital Signal 1|T1]] or [[E-carrier|E1]]. Between telephone company switches, the signaling is performed via [[Signaling System No 7|SS7]]. Normally, a PBX is connected via a T1 with [[robbed-bit signaling]] to indicate on-hook or off-hook conditions and [[multi-frequency|MF]] and [[dual-tone multi-frequency|DTMF]] tones to encode the destination number. ISDN is much better because messages can be sent much more quickly than by trying to encode numbers as long (100 [[Millisecond|ms]] per digit) tone sequences. This results in faster call setup times. Also, a greater number of features are available and fraud is reduced. | ||
In common use, ISDN is often limited to usage to [[Q.931]] and related protocols, which are a set of [[Signaling (telecommunications)|signaling protocol]]s establishing and breaking circuit-switched connections, and for advanced [[calling feature]]s for the user.<ref>{{cite journal |last1 =Aaron |first1 =R | last2 = Wyndrum | first2 = R |title= Future trends |journal= IEEE Communications Magazine |date=March 1986 | volume = 24 | issue = 3 | pages = 38–43 | publisher = [[AT&T Bell Laboratories]] |doi= 10.1109/MCOM.1986.1093028}}</ref> Another usage was the deployment of [[videoconference]] systems, where a direct end-to-end connection is desirable. ISDN uses the [[H.320]] standard for [[audio coding]] and [[video coding]]. | In common use, ISDN is often limited to usage to [[Q.931]] and related protocols, which are a set of [[Signaling (telecommunications)|signaling protocol]]s establishing and breaking circuit-switched connections, and for advanced [[calling feature]]s for the user.<ref>{{cite journal |last1 =Aaron |first1 =R | last2 = Wyndrum | first2 = R |title= Future trends |journal= IEEE Communications Magazine |date=March 1986 | volume = 24 | issue = 3 | pages = 38–43 | publisher = [[AT&T Bell Laboratories]] |doi= 10.1109/MCOM.1986.1093028 |bibcode =1986IComM..24c..38A }}</ref> Another usage was the deployment of [[videoconference]] systems, where a direct end-to-end connection is desirable. ISDN uses the [[H.320]] standard for [[audio coding]] and [[video coding]]. | ||
ISDN is also used as a smart-network technology intended to add new services to the [[public switched telephone network]] (PSTN) by giving users direct access to end-to-end circuit-switched digital services and as a backup or failsafe circuit solution for critical use data circuits. | ISDN is also used as a smart-network technology intended to add new services to the [[public switched telephone network]] (PSTN) by giving users direct access to end-to-end circuit-switched digital services and as a backup or failsafe circuit solution for critical use data circuits. | ||
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=== Germany === | === Germany === | ||
In [[Germany]], ISDN was very popular with an installed base of 25 million channels (29% of all subscriber lines in Germany as of 2003 and 20% of all ISDN channels worldwide). Due to the success of ISDN, the number of installed analog lines was decreasing. [[Deutsche Telekom]] (DTAG) offered both BRI and PRI. Competing phone companies often offered ISDN only and no analog lines. However, these operators generally offered free hardware that also allows the use of POTS equipment, such as NTBAs ("[[:de:Network Termination for ISDN Basic rate Access|Network Termination for ISDN Basic rate Access]]": small devices that bridge the two-wire UK0 line to the four-wire S0 bus) with integrated [[terminal adapter]]s. Because of the widespread availability of ADSL services, ISDN was primarily used for voice and fax traffic. | In [[Germany]], ISDN was very popular with an installed base of 25 million channels (29% of all subscriber lines in Germany as of 2003 and 20% of all ISDN channels worldwide). Due to the success of ISDN, the number of installed analog lines was decreasing. [[Deutsche Telekom]] (DTAG) offered both BRI and PRI. Competing phone companies often offered ISDN only and no analog lines. However, these operators generally offered free hardware that also allows the use of POTS equipment, such as NTBAs ("[[:de:Network Termination for ISDN Basic rate Access|Network Termination for ISDN Basic rate Access]]": small devices that bridge the two-wire UK0 line to the four-wire S0 bus) with integrated [[terminal adapter]]s. Because of the widespread availability of ADSL services, ISDN was primarily used for voice and fax traffic. | ||
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Since approximately 2010, most German operators have offered more and more VoIP on top of DSL lines and ceased offering ISDN lines. New ISDN lines have been no longer available in Germany since 2018, existing ISDN lines were phased out from 2016 onwards and existing customers were encouraged to move to DSL-based VoIP products. | Since approximately 2010, most German operators have offered more and more VoIP on top of DSL lines and ceased offering ISDN lines. New ISDN lines have been no longer available in Germany since 2018, existing ISDN lines were phased out from 2016 onwards and existing customers were encouraged to move to DSL-based VoIP products. | ||
Deutsche Telekom intended to phase-out by 2018<ref>{{cite web|last1=Niek Jan van Damme|title=Deutsche Telekom - 100% IP by 2018|website=[[YouTube]] |url=https://www.youtube.com/watch?v=3JNSTrNFgCM| archive-url=https://ghostarchive.org/varchive/youtube/20211211/3JNSTrNFgCM| archive-date=2021-12-11 | url-status=live|access-date=7 May 2016|date=16 March 2014}}{{cbignore}}</ref> but announced the complete transition in 2020 | Deutsche Telekom intended to phase-out by 2018<ref>{{cite web|last1=Niek Jan van Damme|title=Deutsche Telekom - 100% IP by 2018|website=[[YouTube]] |url=https://www.youtube.com/watch?v=3JNSTrNFgCM| archive-url=https://ghostarchive.org/varchive/youtube/20211211/3JNSTrNFgCM| archive-date=2021-12-11 | url-status=live|access-date=7 May 2016|date=16 March 2014}}{{cbignore}}</ref> but announced the complete transition in 2020.<ref>{{Cite web |last=AG |first=Deutsche Telekom |date=2020-03-02 |title=Five facts about the IP migration |url=https://www.telekom.com/en/company/details/five-facts-about-the-ip-migration-596110 |access-date=2025-04-13 |website=www.telekom.com |language=en}}</ref> Other providers like Vodafone estimate to have their phase-out completed by 2022. | ||
=== Greece === | === Greece === | ||
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In the [[United Kingdom]], [[BT Group|British Telecom]] (BT) provides ISDN2e (BRI) as well as ISDN30 (PRI). Until April 2006, they also offered services named [[BT Highway|Home Highway and Business Highway]], which were BRI ISDN-based services that offered integrated analogue connectivity as well as ISDN. Later versions of the Highway products also included built-in [[USB]] sockets for direct computer access. Home Highway was bought by many home users, usually for Internet connection, although not as fast as ADSL, because it was available before ADSL and in places where ADSL does not reach. | In the [[United Kingdom]], [[BT Group|British Telecom]] (BT) provides ISDN2e (BRI) as well as ISDN30 (PRI). Until April 2006, they also offered services named [[BT Highway|Home Highway and Business Highway]], which were BRI ISDN-based services that offered integrated analogue connectivity as well as ISDN. Later versions of the Highway products also included built-in [[USB]] sockets for direct computer access. Home Highway was bought by many home users, usually for Internet connection, although not as fast as ADSL, because it was available before ADSL and in places where ADSL does not reach. | ||
In early 2015, BT announced their intention to retire the UK's ISDN infrastructure by 2025.<ref>{{Cite web|title=The Big Switch Off|url=http://www.tmc-telecom.co.uk/News/18/the-big-switch-off|access-date=2021-01-29|website=www.tmc-telecom.co.uk|language=en}}</ref> | In early 2015, BT announced their intention to retire the UK's ISDN infrastructure by 2025.<ref>{{Cite web |title=The Big Switch Off |url=http://www.tmc-telecom.co.uk/News/18/the-big-switch-off |url-status=usurped |archive-url=https://web.archive.org/web/20191215010019/http://www.tmc-telecom.co.uk/News/18/the-big-switch-off |archive-date=15 December 2019 |access-date=2021-01-29 |website=www.tmc-telecom.co.uk |language=en}}</ref> The shutdown period has since been extended to 31 January 2027 in line with the shutdown of [[Public switched telephone network|PSTN]].<ref>{{Cite web |date=2 October 2025 |title=PSTN and ISDN Switch Off UK 2027: How to Prepare and Transition |url=https://tawk.network/bt-group-announces-delay-of-pstn-and-isdn-switch-off/ |url-status=live |archive-url=https://archive.today/20260121175336/https://tawk.network/bt-group-announces-delay-of-pstn-and-isdn-switch-off/ |archive-date=21 January 2026 |access-date=21 January 2026 |website=Tawk Network}}</ref> | ||
=== United States and Canada === | === United States and Canada === | ||
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ISDN-BRI never gained popularity as a general use telephone access technology in Canada and the US, and remains a niche product. The service was seen as "a solution in search of a problem",<ref>{{Citation | journal = Computing Japan Magazine | date = September–October 1995 | type = article | title = ISDN: A Solution in Search of a Problem | url = http://www.japaninc.com/cpj/magazine/issues/1995/sep95/09isdn.html | access-date = 2009-06-05 | archive-date = 2011-07-18 | archive-url = https://web.archive.org/web/20110718194415/http://www.japaninc.com/cpj/magazine/issues/1995/sep95/09isdn.html | url-status = live }}.</ref> and the extensive array of options and features were difficult for customers to understand and use. ISDN has long been known by derogatory [[backronym]]s highlighting these issues, such as ''It Still Does Nothing'', ''Innovations Subscribers Don't Need'', and ''I Still Don't kNow'',<ref>{{cite book| first = James Harry | last = Green| title = The Irwin Handbook of Telecommunications | url = https://books.google.com/books?id=L1iJaXDV89gC&pg=PA262| edition = 5| access-date = 12 May 2012 | date= 26 October 2005 | publisher= McGraw-Hill Professional| isbn = 978-0-07-145222-9| page = 770}}</ref><ref>{{cite book| first1=Madeline | last1 = Bodin| first2= Keith | last2 = Dawson|title= The Call Center Dictionary: The Complete Guide to Call Center & Customer Support Technology Solutions| url = https://books.google.com/books?id=CTXhqkFDQKQC&pg=PA101 | access-date= 12 May 2012 | date= 3 January 2002 | publisher = Focal Press|isbn=978-1-57820-095-5|page= 227}}</ref> or, from the supposed standpoint of telephone companies, ''I Smell Dollars Now''.<ref>[https://books.google.com/books?id=Idg9EcuKlT4C&dq=isdn+i+smell+dollars+now&pg=PA91 Telecompetition: The Free Market Road to the Information Highway], Lawrence Gasman, p. 91</ref> | ISDN-BRI never gained popularity as a general use telephone access technology in Canada and the US, and remains a niche product. The service was seen as "a solution in search of a problem",<ref>{{Citation | journal = Computing Japan Magazine | date = September–October 1995 | type = article | title = ISDN: A Solution in Search of a Problem | url = http://www.japaninc.com/cpj/magazine/issues/1995/sep95/09isdn.html | access-date = 2009-06-05 | archive-date = 2011-07-18 | archive-url = https://web.archive.org/web/20110718194415/http://www.japaninc.com/cpj/magazine/issues/1995/sep95/09isdn.html | url-status = live }}.</ref> and the extensive array of options and features were difficult for customers to understand and use. ISDN has long been known by derogatory [[backronym]]s highlighting these issues, such as ''It Still Does Nothing'', ''Innovations Subscribers Don't Need'', and ''I Still Don't kNow'',<ref>{{cite book| first = James Harry | last = Green| title = The Irwin Handbook of Telecommunications | url = https://books.google.com/books?id=L1iJaXDV89gC&pg=PA262| edition = 5| access-date = 12 May 2012 | date= 26 October 2005 | publisher= McGraw-Hill Professional| isbn = 978-0-07-145222-9| page = 770}}</ref><ref>{{cite book| first1=Madeline | last1 = Bodin| first2= Keith | last2 = Dawson|title= The Call Center Dictionary: The Complete Guide to Call Center & Customer Support Technology Solutions| url = https://books.google.com/books?id=CTXhqkFDQKQC&pg=PA101 | access-date= 12 May 2012 | date= 3 January 2002 | publisher = Focal Press|isbn=978-1-57820-095-5|page= 227}}</ref> or, from the supposed standpoint of telephone companies, ''I Smell Dollars Now''.<ref>[https://books.google.com/books?id=Idg9EcuKlT4C&dq=isdn+i+smell+dollars+now&pg=PA91 Telecompetition: The Free Market Road to the Information Highway], Lawrence Gasman, p. 91</ref> | ||
Although various minimum bandwidths have been used in definitions of [[Broadband Internet access]], ranging up from {{nowrap|64 kbit/s}} up to {{nowrap|1.0 Mbit/s}}, the 2006 OECD report is typical by defining broadband as having download data transfer rates equal to or faster than {{nowrap|256 kbit/s}},<ref>{{Citation | url = http://www.oecd.org/document/7/0,3343,en_2649_34223_38446855_1_1_1_1,00.html | year = 2006 | publisher = OECD | title = Broadband Statistics | type = report | access-date = 2012-12-10 | archive-date = 2011-05-27 | archive-url = https://web.archive.org/web/20110527044720/http://www.oecd.org/document/7/0,3343,en_2649_34223_38446855_1_1_1_1,00.html | url-status = live }}</ref> while the United States FCC, | Although various minimum bandwidths have been used in definitions of [[Broadband Internet access]], ranging up from {{nowrap|64 kbit/s}} up to {{nowrap|1.0 Mbit/s}}, the 2006 OECD report is typical by defining broadband as having download data transfer rates equal to or faster than {{nowrap|256 kbit/s}},<ref>{{Citation | url = http://www.oecd.org/document/7/0,3343,en_2649_34223_38446855_1_1_1_1,00.html | year = 2006 | publisher = OECD | title = Broadband Statistics | type = report | access-date = 2012-12-10 | archive-date = 2011-05-27 | archive-url = https://web.archive.org/web/20110527044720/http://www.oecd.org/document/7/0,3343,en_2649_34223_38446855_1_1_1_1,00.html | url-status = live }}</ref> while the United States FCC, in 2008, defined broadband as anything above {{nowrap|768 kbit/s}}.<ref>{{Citation | url = http://hraunfoss.fcc.gov/edocs_public/attachmatch/DOC-280909A2.doc | title = Statement of Chairman | first = Kevin J | last = Martin | publisher = FCC | place = [[United States of America|US]] | format = [[Microsoft|MS]] [[Microsoft Word|Word]] doc | access-date = 2012-12-10 | archive-date = 2011-10-17 | archive-url = https://web.archive.org/web/20111017203347/http://hraunfoss.fcc.gov/edocs_public/attachmatch/DOC-280909A2.doc | url-status = dead }}.</ref><ref name = "Engadget">{{Citation | newspaper = Engadget | url = https://www.engadget.com/2008/03/19/fcc-redefines-broadband-to-mean-768kbps-fast-to-mean-kinda/ | title = FCC redefines "broadband" to mean {{nowrap|768 kbit/s}}, "fast" to mean "kinda slow" | date = 2008-03-19 | access-date = 2017-09-01 | archive-date = 2021-06-06 | archive-url = https://web.archive.org/web/20210606030829/https://www.engadget.com/2008-03-19-fcc-redefines-broadband-to-mean-768kbps-fast-to-mean-kinda.html | url-status = live }}.</ref> Once the term "broadband" came to be associated with data rates incoming to the customer at {{nowrap|256 kbit/s}} or more, and alternatives like [[ADSL]] grew in popularity, the consumer market for BRI did not develop and is effectively discontinued. Its only remaining advantage that it had, is that while ADSL has a functional distance limitation and can use [[ADSL loop extender]]s, BRI had a greater limit and could use repeaters. As such, BRI would have possibly been acceptable for customers who were too remote for ADSL. Widespread use of BRI was further stymied by some small North American [[Competitive local exchange carrier|CLEC]]s such as [[CenturyTel]] having given up on it and not providing Internet access using it.<ref>{{Citation | publisher = CenturyTel | title = Internet Access service offerings | quote = You may not obtain Internet services over ISDN lines (BRI or PRI), dedicated circuits or special service circuits | contribution = Disclaimer | url = http://www.centurytel.com/Pages/Disclaimers/internetDisclaimer.jsp | access-date = 2009-06-07 | archive-date = 2008-12-25 | archive-url = https://web.archive.org/web/20081225063242/http://www.centurytel.com/Pages/Disclaimers/internetDisclaimer.jsp | url-status = dead }}.</ref> However, AT&T would still have been able to have installed an ISDN BRI line anywhere in most states a normal analog line could have been placed (especially the former [[Southwestern Bell|SBC/SWB]] territory) until discontinuation in 2021.<ref name=":0" />{{update|date=December 2024}} | ||
ISDN-BRI is currently primarily used in industries with specialized and very specific needs. High-end [[videoconferencing]] hardware can bond up to 8 B-channels together (using a BRI circuit for every 2 channels) to provide digital, circuit-switched video connections to almost anywhere in the world. This is very expensive, and is being replaced by IP-based conferencing, but where cost concern is less of an issue than predictable quality and where a [[Quality of service|QoS]]-enabled IP does not exist, BRI is the preferred choice. | ISDN-BRI is currently primarily used in industries with specialized and very specific needs. High-end [[videoconferencing]] hardware can bond up to 8 B-channels together (using a BRI circuit for every 2 channels) to provide digital, circuit-switched video connections to almost anywhere in the world. This is very expensive, and is being replaced by IP-based conferencing, but where cost concern is less of an issue than predictable quality and where a [[Quality of service|QoS]]-enabled IP does not exist, BRI is the preferred choice. | ||
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Most modern non-[[VoIP]] PBXs use ISDN-PRI circuits. These are connected via [[T-carrier|T1 lines]] with the central office switch, replacing older analog two-way and [[direct inward dialing]] (DID) trunks. PRI is capable of delivering [[Calling Line Identification]] (CLID) in both directions so that the telephone number of an extension, rather than a company's main number, can be sent. It is still commonly used in [[recording studio]]s and some [[radio program]]s, when a [[voice-over]] actor or host is in one studio conducting [[remote work]], but the director and producer are in a studio at another location.<ref name="Talkers 2013-03-28"/> The ISDN protocol delivers channelized, not-over-the-Internet service, powerful call setup and routing features, faster setup and tear down, superior audio fidelity as compared to [[plain old telephone service]] (POTS), lower delay and, at higher densities, lower cost. | Most modern non-[[VoIP]] PBXs use ISDN-PRI circuits. These are connected via [[T-carrier|T1 lines]] with the central office switch, replacing older analog two-way and [[direct inward dialing]] (DID) trunks. PRI is capable of delivering [[Calling Line Identification]] (CLID) in both directions so that the telephone number of an extension, rather than a company's main number, can be sent. It is still commonly used in [[recording studio]]s and some [[radio program]]s, when a [[voice-over]] actor or host is in one studio conducting [[remote work]], but the director and producer are in a studio at another location.<ref name="Talkers 2013-03-28"/> The ISDN protocol delivers channelized, not-over-the-Internet service, powerful call setup and routing features, faster setup and tear down, superior audio fidelity as compared to [[plain old telephone service]] (POTS), lower delay and, at higher densities, lower cost. | ||
In 2013, [[Verizon]] announced it would no longer take orders for ISDN service in the [[Northeastern United States]] | In 2013, [[Verizon]] announced it would no longer take orders for ISDN service in the [[Northeastern United States]]<ref name="Talkers 2013-03-28" /> and Verizon's remaining ISDN services were finally discontinued and shutdown throughout 2025<ref>{{Cite web |last=Thomas |first=Sharon |date=11 February 2025 |title=Services to Be Withdrawn in Massachusetts, New Jersey, New York and Rhode Island |url=https://ripuc.ri.gov/sites/g/files/xkgbur841/files/2025-02/Verizon%20RI%20Tariff%2018%20NTRevision%202025%200313.pdf |access-date=27 April 2026 |website=Rhode Island Public Utilities Commission}}</ref> and 2026.<ref>{{Cite web |last=Thomas |first=Sharon |date=13 January 2026 |title=Services to be Withdrawn: Switched/Unswitched and Intra-LATA DS0 Services |url=https://ripuc.ri.gov/sites/g/files/xkgbur841/files/2026-02/RI18%202026%200213%20Sunsetting%20r.pdf |access-date=27 April 2026 |website=Rhode Island Public Utilities Commission}}</ref> In 2019, [[iHeartMedia]], the largest network of radio stations within the [[United States]] completed the transition from ISDN to [[Session Initiation Protocol|SIP]] for their internal broadcast circuits. <ref>{{Cite web |last=George |first=Steve |date=2019-08-07 |title=iHeartMedia Builds Audio Transport Platform With Barix |url=https://www.radioworld.com/tech-and-gear/buyers-guide/iheart-audio-transport-barix |access-date=2026-04-25 |website=Radio World |language=en-US}}</ref> In 2021, [[AT&T]] finally discontinued ISDN service, marking the final consumer facing network service provider to discontinue ISDN for any home or small business use in the entire US. <ref name=":0">{{Cite web |last=Bialik |first=David |date=2021-09-04 |title=Goodbye ISDN, Hello Streaming |url=https://www.radioworld.com/columns-and-views/guest-commentaries/goodbye-isdn-hello-streaming |access-date=2026-04-25 |website=Radio World |language=en-US}}</ref> | ||
== See also == | == See also == | ||
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{{wikibooks|Nets, Webs and the Information Infrastructure}} | {{wikibooks|Nets, Webs and the Information Infrastructure}} | ||
* {{cite journal | first = John | last = Cioffi | title = Lighting up copper | journal = IEEE Communications Magazine | volume = 49 | issue = 5 | date = May 2011 | pages = 30–43 | doi = 10.1109/MCOM.2011.5762795 | | * {{cite journal | first = John | last = Cioffi | title = Lighting up copper | journal = IEEE Communications Magazine | volume = 49 | issue = 5 | date = May 2011 | pages = 30–43 | doi = 10.1109/MCOM.2011.5762795 | bibcode = 2011IComM..49e..30C | s2cid = 8661205 }} | ||
* {{Citation | url = http://www.itu.int/rec/T-REC-I/e | type = list | title = Published recommendations available in English, French and Spanish | publisher = ITU | access-date = 2008-08-19 | archive-date = 2012-08-27 | archive-url = https://web.archive.org/web/20120827155842/http://www.itu.int/rec/T-REC-I/e | url-status = live }} | * {{Citation | url = http://www.itu.int/rec/T-REC-I/e | type = list | title = Published recommendations available in English, French and Spanish | publisher = ITU | access-date = 2008-08-19 | archive-date = 2012-08-27 | archive-url = https://web.archive.org/web/20120827155842/http://www.itu.int/rec/T-REC-I/e | url-status = live }} | ||
* {{Citation | url = http://hea-www.harvard.edu/~fine/ISDN/ | last = Fine | title = ISDN | publisher = Harvard | access-date = 2003-08-14 | archive-date = 2010-08-18 | archive-url = https://web.archive.org/web/20100818174908/http://hea-www.harvard.edu/~fine/ISDN/ | url-status = live }} | * {{Citation | url = http://hea-www.harvard.edu/~fine/ISDN/ | last = Fine | title = ISDN | publisher = Harvard | access-date = 2003-08-14 | archive-date = 2010-08-18 | archive-url = https://web.archive.org/web/20100818174908/http://hea-www.harvard.edu/~fine/ISDN/ | url-status = live }} | ||