This is the status of the DSL loop to the subscriber.
1=Loop is down.
2=Frx card has achieved physical layer activation with
the first BRITE card or the NT1 if there are no BRITE cards.
3=Link is up but Annex-D is still inactive. The ACT bit has
been exchanged with the NT1 indicating a clear channel path
to the customer has been established. Ports running protocols
(i.e. PPP) that do not support Annex-D will never be in this
state.
4=Link is fully up. Annex-D (if appropriate) is active.