Resyncs

[#1]

Are there events other than the interruption of the power supply. or something like too much noise that can xause a resync? Just curious

[#2]

Yes, too much noise or high interference on a DSL line can cause equipment to loose track of the DSL signal and cause a resync to the exchange.

At this time of year, christmas lights are good for this kind of thing!
You can also interrupt the DSL cable in some way, be it by unplugging it from the router or someone digging through the phoneline to your home etc. This would also be a resync event.

[#3]

We've just migrated our service to a new line. The first time we made a phone call caused a re-synch to a slightly lower speed.
I'd expect to see a number of things causing a re-synch during the initial period on a new line untill a stable rate is found.

[#4]

Quote from: MrToast

The first time we made a phone call caused a re-synch to a slightly lower speed.

Making phone calls should not affect your adsl sync (unless not correctly filtered) 

[#5]

No filter is perfect.
The first synch speed on the new line was 7200 and it dropped to 6848.
I'd say thats reasonable if the system started up against the limits for noise on the line. It hasn't dropped again for subsequent phone usage.