Billion BiPAC 7700N User Manual page 110

Select the Test Mode, or leave it as default.
Tone Selection: suggesting you to leave it as default or let it configured by an advanced user.
The frequency band of ADSL is split up into 256 separate tones, each spaced 4.3125 kHz apart.
With each tone carrying separate data, the technique operates as if 256 separate modems were
running in parallel. The tone range is from 0 to 31 for upstream and from 32 to 255 for
downstream。
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