Editing ISDN (section)

=== Replacement by ADSL ===

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}}

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.