G.992.3 Annex J
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Annex J is a specification in ITU-T recommendations G.992.3 and G.992.5 for all digital mode ADSL with improved spectral compatibility with ADSL over ISDN, which means that it is a type of naked DSL which will not disturb existing Annex B ADSL services in the same cable binder.
This specification has the same upstream/downstream frequency split of 276 kHz as Annex B, but does not have lower frequency limit of 138 kHz, allowing upstream bandwidth to be increased from 1.8 Mbit/s to 3.5 Mbit/s. This is similar to Annex M, but Annex J can not have POTS on the same line.
Deutsche Telekom started deploying Annex J in 2011 (marketed as "All-IP" service), Vodafone Germany followed suit in April 2015 (marketed as quality improvements).
![](http://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/ADSL_annex_overview.svg/600px-ADSL_annex_overview.svg.png)
Legend POTS/ISDN Guard Band Upstream Downstream ADSL/ADSL2 Additional Downstream ADSL2+ |