I've just upgraded the IOS on my 877W.
It used to show the DSL lien attenuation as 39dB, but since the upgrade from 12.4.4T to 12.4.9T the attenuation is shown as 47db.
I have tried two other routers - a Draytek & a Netgear on the same line, both report 39db so I think it safe to say that figure is correct.
I wonder if anyone else has seen this problem?
Regards