said by leibold:In order for the DSL Ring idea to work DSL signals need to be retransmitted. This means that the CN will need to receive DSL signals at the same frequencies (from the CO) at which it will forward it into the Ring (to the CPE) and vice versa. If the HGW are active components (retransmitting instead of just passing through) the same problem exists there as well. I'm not sure how realistic it is under real life conditions to avoid the feedback problems (from local transmitter to receiver) this is going to cause.
By placing a notch filter on the line, you can allow the voice coming from the exchange to pass through the line while effectivley cutting the line at dsl frequencies. Or you could feed the voice circuits from the exchange by running a PCM encoded system or voip over the top of the DSL signals between the local ring and the exchange backhaul. 
