https://en.wikipedia.org/wiki/Asymmetric_digital_subscriber_line#Operation https://en.wikipedia.org/wiki/Asymmetric_digital_subscriber_... https://en.wikipedia

https://en.wikipedia.org/wiki/Asymmetric_digital_subscriber_line#Operation https://en.wikipedia.org/wiki/Asymmetric_digital_subscriber_... https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_cor... As I understand it, the endpoints test a range of frequency blocks (or "bins") and only use the ones where there is sufficient signal-to-noise. This is dependent on line conditions.