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.[1][2]
| Status | In force |
|---|---|
| Organization | ITU-T |
| Base standards | G.992.3 |
| Domain | telecommunications |
| License | Freely available |
| Website | https://www.itu.int/rec/T-REC-G.992.3/ |
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, Vodafone Germany followed suit in April 2015 (marketed as quality improvements).
Legend
POTS/ISDN
Guard Band
Upstream
Downstream ADSL/ADSL2
Additional Downstream ADSL2+
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