The upper diagram shows the signal-to-noise ratio at each individual downstream carrier.

The lower diagram is a graph of the modulation depth. The higher the modulation depth, the more bits per time unit are transmitted by the carrier.

A carrier corresponds to a frequency band of 4312.5 Hz. The ADSL transmission area is subdivided into 256 carriers, of which 32 may be used for upstream (to the Internet) and 190 for downstream transmission.

The red marking indicates the pilot tone which is used to synchronize the DSL-Controller with the exchange.